Pub Date : 2024-07-05DOI: 10.2113/2024/lithosphere_2023_322
Xingzong Liu, Bin Gong, Kezhi Song, Hao Liu
An indirect testing method for determining the tensile strength of rock-like heterogeneous materials is proposed. The realistic failure process analysis method, which can consider material inhomogeneity, is applied to model the failure process of the square plate containing a circular hole under uniaxial compression. The influence of plate thickness and applied loads on the maximum tensile stress is investigated, and the tensile strength equation is deduced. Meanwhile, the initial cracking loads are obtained by the corresponding physical tests, and the tensile strengths are determined by substituting the initial cracking loads into the developed tensile strength equation. The values predicted by the newly proposed method are almost identical to those of the direct tensile tests. Furthermore, the proposed method can give the relatively small tensile strength error with the direct tensile test in comparison to the other test methods, which indicates that the proposed method is effective and valid for determining the tensile strength of rock-like heterogeneous materials.During the design process in geotechnical engineering, a crucial parameter is the tensile strength of rock [1, 2]. Direct tensile testing (DTT) is one of the most reliable methods for determining this strength and is independent of the constitutive response of a material [3, 4]. However, performing valid direct tensile tests is challenging. Preparing the dog bone-shaped specimens required for these tests is difficult, and stress concentrations at the ends of specimens often lead to failure away from the midpoint [5-7]. To use the direct methods, empirical equations from the literature are typically used, and/or numerous rock samples are tested in the laboratory. However, physical experiment is usually time-consuming and costly. Meanwhile, some indirect methods for assessing the tensile strength have been proposed [8-10]. The classical indirect testing methods include the ring test [11-13], wedge splitting test [14], three-point or four-point beam bending tests [15-17], hollow cylinder test [18], unconfined expansion test [19], point load test [20, 21], and Brazilian test [22, 23]. The Brazilian split test (BST) is the most commonly used indirect method to determine the tensile strength of rock-like materials, which is the recommended test method by the International Society for Rock Mechanics (ISRM) [24, 25]. However, the Brazilian test has been criticized since it was initially proposed due to the test results varying with loading rate [26-28], specimen size [29-31], experimental materials [32, 33], jaw’s curvature [34], and testing standards [35]. In order to carry out a valid Brazilian test, researchers proposed plenty of modified Brazilian test methods [36-40].Several factors control the tensile strength of rock materials, for example discontinuities, foliation, lamination, mineral composition, cementing material, hardness, and porosity [41-43]. Discontinuities, foliation, and la
{"title":"Indirect Tensile Strength Test on Heterogeneous Rock Using Square Plate Sample with a Circular Hole","authors":"Xingzong Liu, Bin Gong, Kezhi Song, Hao Liu","doi":"10.2113/2024/lithosphere_2023_322","DOIUrl":"https://doi.org/10.2113/2024/lithosphere_2023_322","url":null,"abstract":"An indirect testing method for determining the tensile strength of rock-like heterogeneous materials is proposed. The realistic failure process analysis method, which can consider material inhomogeneity, is applied to model the failure process of the square plate containing a circular hole under uniaxial compression. The influence of plate thickness and applied loads on the maximum tensile stress is investigated, and the tensile strength equation is deduced. Meanwhile, the initial cracking loads are obtained by the corresponding physical tests, and the tensile strengths are determined by substituting the initial cracking loads into the developed tensile strength equation. The values predicted by the newly proposed method are almost identical to those of the direct tensile tests. Furthermore, the proposed method can give the relatively small tensile strength error with the direct tensile test in comparison to the other test methods, which indicates that the proposed method is effective and valid for determining the tensile strength of rock-like heterogeneous materials.During the design process in geotechnical engineering, a crucial parameter is the tensile strength of rock [1, 2]. Direct tensile testing (DTT) is one of the most reliable methods for determining this strength and is independent of the constitutive response of a material [3, 4]. However, performing valid direct tensile tests is challenging. Preparing the dog bone-shaped specimens required for these tests is difficult, and stress concentrations at the ends of specimens often lead to failure away from the midpoint [5-7]. To use the direct methods, empirical equations from the literature are typically used, and/or numerous rock samples are tested in the laboratory. However, physical experiment is usually time-consuming and costly. Meanwhile, some indirect methods for assessing the tensile strength have been proposed [8-10]. The classical indirect testing methods include the ring test [11-13], wedge splitting test [14], three-point or four-point beam bending tests [15-17], hollow cylinder test [18], unconfined expansion test [19], point load test [20, 21], and Brazilian test [22, 23]. The Brazilian split test (BST) is the most commonly used indirect method to determine the tensile strength of rock-like materials, which is the recommended test method by the International Society for Rock Mechanics (ISRM) [24, 25]. However, the Brazilian test has been criticized since it was initially proposed due to the test results varying with loading rate [26-28], specimen size [29-31], experimental materials [32, 33], jaw’s curvature [34], and testing standards [35]. In order to carry out a valid Brazilian test, researchers proposed plenty of modified Brazilian test methods [36-40].Several factors control the tensile strength of rock materials, for example discontinuities, foliation, lamination, mineral composition, cementing material, hardness, and porosity [41-43]. Discontinuities, foliation, and la","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":"78 1","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141743164","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-05DOI: 10.2113/2024/lithosphere_2024_117
Andrew Birkey, Heather A. Ford, Megan Anderson, Joseph S. Byrnes, Maximiliano J. Bezada, Maxim Shapovalov
Dense seismic arrays such as EarthScope’s Transportable Array (TA) have enabled high-resolution seismic observations that show the structure of cratonic lithosphere is more heterogeneous and complex than previously assumed. In this study, we pair TA data with data from the Bighorn Arch Seismic Experiment and the Crust and lithosphere Investigation of the Easternmost expression of the Laramide Orogeny (CIELO) to provide unprecedented detail on the seismic anisotropic structure of the eastern margin of the Wyoming Craton, where several orogens emerged from nominally strong cratonic lithosphere during the Laramide Orogeny. In this study, we use the splitting of teleseismic shear waves to characterize fabrics associated with deformation in the Earth’s crust and mantle. We constrain distinct anisotropic domains in the study area, and forward modeling shows that each of these domains can be explained by a single layer of anisotropy. Most significantly, we find a fast direction in the southern part of the Powder River Basin, which we refer to as the Thunder Basin Block (TBB), that deviates from absolute plate motion (APM). This change in splitting behavior coincides with changes in other modeled geophysical observations, such as active source P-wave velocity models, potential field modeling, and seismic attenuation analysis, which all show a significant change moving from the Bighorn Mountains to the TBB. We argue that these results correspond to structure predating the Laramide Orogeny, and most likely indicate a Neoarchean boundary preserved within the lithosphere.The Wyoming Craton is an Archean to Proterozoic block of lithosphere situated in the center of the North American continent (Figure 1) often divided into three main subregions: in decreasing order of age, the Montana metasedimentary province in the northwest, the Beartooth–Bighorn magmatic zone across the middle, and the southern accreted terranes in the southeast [1]. By ~2.5 Ga, all three subregions were cratonized and assembled as a distinct block of lithosphere [2]. Following cratonization, the Wyoming Craton’s interaction with the other cratons of Laurentia is debated. There is general agreement that terminal collision in Northern Laurentia between the Superior Craton, Hearne-Rae Craton (for location, Figure 1), and Slave Craton of northwestern Canada began earlier (~1.815 to 1.780 Ga) than in southern Laurentia between the Wyoming and Superior cratons (~1.750 to 1.700 Ga). It is unclear whether this represents one orogenic event (i.e. the Trans-Hudson Orogeny [THO]) or several discrete events, with some authors referring to the southern portion of the THO as the Black Hills or Dakotan Orogeny [3-5]. Following the formation of Laurentia, the Wyoming Craton was tectonically quiescent until ~80 Ma, when flattening of the Farallon slab initiated the Laramide Orogeny [6-9]. Cratons are assumed to be stable, thick lithosphere resistant to deformation or destruction under most circumstances [
高密度地震阵列（如 EarthScope 的可移动阵列 (TA)）实现了高分辨率的地震观测，显示板块岩石圈的结构比以前假设的更加异质和复杂。在本研究中，我们将可移动阵列数据与比格霍恩拱地震实验数据以及拉氏造山运动最东端地壳与岩石圈调查（CIELO）数据配对，提供了怀俄明克拉通东缘地震各向异性结构的前所未有的细节，在拉氏造山运动期间，怀俄明克拉通东缘从名义上坚固的板块岩石圈中产生了几个造山运动。在这项研究中，我们利用远震剪切波的分裂来描述与地壳和地幔变形相关的结构。我们对研究区域内不同的各向异性域进行了约束，前向建模显示，这些域中的每一个都可以用单层各向异性来解释。最重要的是，我们在粉河盆地南部发现了一个偏离绝对板块运动（APM）的快速方向，我们将其称为雷霆盆地块（TBB）。这种分裂行为的变化与其他地球物理观测模型的变化相吻合，如活动源 P 波速度模型、势场模型和地震衰减分析，这些模型都显示了从比格霍恩山脉到 TBB 的显著变化。我们认为，这些结果与拉雷米亚造山运动之前的结构相对应，很可能表明岩石圈中保留了新元古代的边界。怀俄明克拉通是位于北美大陆中心的阿新世至新生代岩石圈块体（图 1），通常被划分为三个主要亚区：按年龄递减顺序，西北部为蒙大拿变质岩带，中部为熊牙-大角山岩浆带，东南部为南部增生地块[1]。到约 2.5 Ga 时，所有这三个亚区都发生了克拉通化，并组合成一个独特的岩石圈块[2]。在克拉通化之后，怀俄明克拉通与劳伦提亚其他克拉通的相互作用还存在争议。人们普遍认为，劳伦提亚北部的苏必利尔克拉通、赫恩-雷克拉通（位置见图1）和加拿大西北部的斯拉夫克拉通之间的末端碰撞（约1.815-1.780Ga）要早于劳伦提亚南部的怀俄明和苏必利尔克拉通之间的碰撞（约1.750-1.700Ga）。目前还不清楚这代表的是一个造山事件（即跨哈德逊造山带[THO]）还是几个独立的事件，一些学者将跨哈德逊造山带的南部称为黑山造山带或达科他造山带[3-5]。劳伦提亚形成后，怀俄明克拉通在构造上一直处于静止状态，直到大约 80 Ma 时，法拉伦板块的扁平化引发了拉里酰胺造山运动[6-9]。人们假定克拉通是稳定、厚实的岩石圈，在大多数情况下可抵抗变形或破坏[10]，但在整个怀俄明克拉通，地壳在拉氏造山运动期间发生了以基底为中心的隆起变形（即风河山脉、花岗岩山脉、猫头鹰溪山脉、比格霍恩拱门、拉拉米山脉和黑山；图 1）。怀俄明克拉通东部边缘的位置仍存在争议：一些研究认为，根据黑山和整个怀俄明克拉通隆起中岩石的阿契安时代[2, 11]，以及来自黑山的锆石碎片的年龄[12]，克拉通延伸穿过黑山。然而，布莱克山的小麋鹿花岗岩[11]与比格霍恩山脉的阿歇安火山岩[13]的年龄相差约 300 Myr。还有人认为比格霍恩拱东部边缘的边界更偏西。这一论点的依据是地壳尺度西倾地震反射体的存在，该反射体可能反映了前寒武纪缝合带与比格霍恩山脉以东的磁接触[14]。磁电研究显示了一个从加拿大北部延伸到夏安带的高导异常[15]。Bedrosian 和 Finn [15] 将其称为北美中原异常，并认为它与 THO 和劳伦提亚的形成有关。这种解释将怀俄明克拉通的东缘置于黑山以东。鉴于这些研究的解释存在分歧，有关怀俄明克拉通的主要悬而未决问题如下：克拉通的东部边缘在哪里？拉氏造山运动是否影响怀俄明克拉通地壳和地幔岩石圈的物理状态（如坚固完整或减弱失稳）？岩石圈的现状与克拉通的形成和演化有何关系？在这项研究中，我们利用剪切波分裂（SWS）来研究这些问题。SWS 可以提供对动态和静态地幔的重要见解。
{"title":"Insight into the Evolution of the Eastern Margin of the Wyoming Craton from Complex, Laterally Variable Shear Wave Splitting","authors":"Andrew Birkey, Heather A. Ford, Megan Anderson, Joseph S. Byrnes, Maximiliano J. Bezada, Maxim Shapovalov","doi":"10.2113/2024/lithosphere_2024_117","DOIUrl":"https://doi.org/10.2113/2024/lithosphere_2024_117","url":null,"abstract":"Dense seismic arrays such as EarthScope’s Transportable Array (TA) have enabled high-resolution seismic observations that show the structure of cratonic lithosphere is more heterogeneous and complex than previously assumed. In this study, we pair TA data with data from the Bighorn Arch Seismic Experiment and the Crust and lithosphere Investigation of the Easternmost expression of the Laramide Orogeny (CIELO) to provide unprecedented detail on the seismic anisotropic structure of the eastern margin of the Wyoming Craton, where several orogens emerged from nominally strong cratonic lithosphere during the Laramide Orogeny. In this study, we use the splitting of teleseismic shear waves to characterize fabrics associated with deformation in the Earth’s crust and mantle. We constrain distinct anisotropic domains in the study area, and forward modeling shows that each of these domains can be explained by a single layer of anisotropy. Most significantly, we find a fast direction in the southern part of the Powder River Basin, which we refer to as the Thunder Basin Block (TBB), that deviates from absolute plate motion (APM). This change in splitting behavior coincides with changes in other modeled geophysical observations, such as active source P-wave velocity models, potential field modeling, and seismic attenuation analysis, which all show a significant change moving from the Bighorn Mountains to the TBB. We argue that these results correspond to structure predating the Laramide Orogeny, and most likely indicate a Neoarchean boundary preserved within the lithosphere.The Wyoming Craton is an Archean to Proterozoic block of lithosphere situated in the center of the North American continent (Figure 1) often divided into three main subregions: in decreasing order of age, the Montana metasedimentary province in the northwest, the Beartooth–Bighorn magmatic zone across the middle, and the southern accreted terranes in the southeast [1]. By ~2.5 Ga, all three subregions were cratonized and assembled as a distinct block of lithosphere [2]. Following cratonization, the Wyoming Craton’s interaction with the other cratons of Laurentia is debated. There is general agreement that terminal collision in Northern Laurentia between the Superior Craton, Hearne-Rae Craton (for location, Figure 1), and Slave Craton of northwestern Canada began earlier (~1.815 to 1.780 Ga) than in southern Laurentia between the Wyoming and Superior cratons (~1.750 to 1.700 Ga). It is unclear whether this represents one orogenic event (i.e. the Trans-Hudson Orogeny [THO]) or several discrete events, with some authors referring to the southern portion of the THO as the Black Hills or Dakotan Orogeny [3-5]. Following the formation of Laurentia, the Wyoming Craton was tectonically quiescent until ~80 Ma, when flattening of the Farallon slab initiated the Laramide Orogeny [6-9]. Cratons are assumed to be stable, thick lithosphere resistant to deformation or destruction under most circumstances [","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":"60 1","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141610819","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-05DOI: 10.2113/2024/lithosphere_2023_305
Xulin Du, Yanchun Su, Renyi Cao, Maojun Fang, Yajun Zheng, Linsong Cheng, Jinchong Zhou
The reliability of forecasts, fracture design, and recovery enhancement strategies in tight oil reservoirs is significantly compromised by the substantial uncertainties associated with fracture characterization. This article introduces an integrated simulation workflow for modeling microseismic fracture networks in tight oil reservoirs, incorporating automatic history matching, as illustrated through a field case study from block Y2 in the Ordos Basin, China. The model stochastically generates the geometry of complex fracture networks (CFNs), including parameters such as length, aperture, inclination and azimuth angles, and spatial positioning, constrained by data from hydraulic fracturing, core analyses, and microseismic monitoring. It employs a stochastic parameterization model to produce an ensemble of initial CFN property realizations and utilizes an advanced Green function-based hierarchical fracture model to accurately depict CFN morphology. The model is further refined, and its uncertainty in fracture characterization is minimized through calibration with an innovative Ensemble Kalman Filter-based assisted history-matching algorithm. Evidence suggests that this comprehensive approach effectively leverages all available geological data, substantially reduces uncertainties in the production process, and aids in identifying the optimal development strategy.Unconventional reservoirs are characterized by ultra-low permeability, high displacement resistance, and low productivity, primarily due to the presence of nanopores and fine throats within the tight matrix. Extensive experience in successfully extracting hydrocarbons from these reservoirs has demonstrated that creating complex fracture networks (CFNs) through multistage hydraulic fracturing represents one of the most effective strategies for boosting oil production [1-3]. However, accurately modeling CFNs presents significant challenges due to substantial uncertainties, leading to increased difficulties in the precise numerical simulation of unconventional reservoirs [4]. Additionally, the disconnect between geological and petroleum engineering disciplines impedes reservoir engineers from fully leveraging geological data in production planning, constituting another significant factor contributing to these challenges.Obtaining fracture morphology through conventional characterization methods is challenging. To enhance the assessment of fracture occurrence, propagation, and the effects of refracturing, microseismic monitoring has been employed to provide essential geological information, as illustrated in Figure 1. While microseismic monitoring data, collected during hydraulic fracturing, enables the analysis of fracture spatial distribution, accurately characterizing CFNs from microseismic events remains a technically demanding task. Currently, methods for reconstructing fracture networks based on microseismic interpretation are categorized into two approaches. The first relies on hydraulic
{"title":"Integrated Simulation for Microseismic Fracture Networks with Automatic History Matching in Tight Oil Development: A Field Case from Block Y2 in Ordos Basin, China","authors":"Xulin Du, Yanchun Su, Renyi Cao, Maojun Fang, Yajun Zheng, Linsong Cheng, Jinchong Zhou","doi":"10.2113/2024/lithosphere_2023_305","DOIUrl":"https://doi.org/10.2113/2024/lithosphere_2023_305","url":null,"abstract":"The reliability of forecasts, fracture design, and recovery enhancement strategies in tight oil reservoirs is significantly compromised by the substantial uncertainties associated with fracture characterization. This article introduces an integrated simulation workflow for modeling microseismic fracture networks in tight oil reservoirs, incorporating automatic history matching, as illustrated through a field case study from block Y2 in the Ordos Basin, China. The model stochastically generates the geometry of complex fracture networks (CFNs), including parameters such as length, aperture, inclination and azimuth angles, and spatial positioning, constrained by data from hydraulic fracturing, core analyses, and microseismic monitoring. It employs a stochastic parameterization model to produce an ensemble of initial CFN property realizations and utilizes an advanced Green function-based hierarchical fracture model to accurately depict CFN morphology. The model is further refined, and its uncertainty in fracture characterization is minimized through calibration with an innovative Ensemble Kalman Filter-based assisted history-matching algorithm. Evidence suggests that this comprehensive approach effectively leverages all available geological data, substantially reduces uncertainties in the production process, and aids in identifying the optimal development strategy.Unconventional reservoirs are characterized by ultra-low permeability, high displacement resistance, and low productivity, primarily due to the presence of nanopores and fine throats within the tight matrix. Extensive experience in successfully extracting hydrocarbons from these reservoirs has demonstrated that creating complex fracture networks (CFNs) through multistage hydraulic fracturing represents one of the most effective strategies for boosting oil production [1-3]. However, accurately modeling CFNs presents significant challenges due to substantial uncertainties, leading to increased difficulties in the precise numerical simulation of unconventional reservoirs [4]. Additionally, the disconnect between geological and petroleum engineering disciplines impedes reservoir engineers from fully leveraging geological data in production planning, constituting another significant factor contributing to these challenges.Obtaining fracture morphology through conventional characterization methods is challenging. To enhance the assessment of fracture occurrence, propagation, and the effects of refracturing, microseismic monitoring has been employed to provide essential geological information, as illustrated in Figure 1. While microseismic monitoring data, collected during hydraulic fracturing, enables the analysis of fracture spatial distribution, accurately characterizing CFNs from microseismic events remains a technically demanding task. Currently, methods for reconstructing fracture networks based on microseismic interpretation are categorized into two approaches. The first relies on hydraulic","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":"88 1","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141570280","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-05DOI: 10.2113/2024/lithosphere_2024_154
Sung Hi Choi, Samuel B. Mukasa, John W. Shervais, Igor S. Puchtel
We report platinum-group element (PGE) and Re concentrations, and Re−Os isotopic data for peridotites and podiform chromitite from the mid-Jurassic Coast Range ophiolite (CRO), California. Our aim is to provide insights into the formation and evolution of the CRO in a fore-arc tectonic setting. The CRO peridotites are divided into two groups: abyssal and supra-subduction zone (SSZ). They have Ir-group PGE concentrations similar to estimates for the primitive mantle and nearly chondritic relative abundances [(Os/Ir)N ≈ 1.1]. Abyssal-type peridotites have slightly subchondritic Pd-group PGE (PPGE)−Re abundances and flat chondrite-normalized patterns, whereas the SSZ-type ones are depleted overall with highly fractionated PPGE−Re patterns. The CRO peridotites have 187Os/188Os values of 0.1188 to 0.1315 (γOs = −8.3 to 1.4) and 187Re/188Os ranging from 0.022 to 0.413. The oxygen fugacity based on the V/Yb ratios of the CRO peridotites is equivalent to the fayalite−magnetite−quartz buffer. The abyssal-type peridotites are residues after ≤5% melting of the primitive upper mantle and represent a remnant of oceanic lithosphere trapped in an SSZ setting but before it was re-melted or modified by subduction processes. The abyssal-type peridotites yield an aluminachron model age of ~1.5 Ga, implying that the CRO mantle had experienced episode(s) of melt extraction before the CRO crust was formed. The SSZ-type peridotites are refractory residues after ~5% to 15% melting. Extraction of fore-arc basalts generated mainly by decompression melting resulted in the SSZ-type peridotites. The chromitite has 187Os/188Os value of 0.1250 (γOs = −3.5) and PGE−Re patterns complementary to that of boninite, indicating a genetic link to fore-arc magmatism.Ophiolites are sections of the Earth’s oceanic crust and the underlying upper mantle that have been tectonically emplaced into continental margins, providing important insights into the processes of plate tectonics, the composition of the oceanic crust and mantle, and the dynamics of Earth’s interior. Ophiolites are also valuable as ore deposits hosting precious metals, including platinum-group elements (PGEs), ferrous metals (Cr, Mn, and Ti), and base metals (Co, Cu, and Ni). The oceanic crust preserved in ophiolites may form in any tectonic setting during the evolution of ocean basins, from the mid-ocean ridge to subduction initiation and final closure [1]. The Coast Range ophiolite (CRO) is a mid-Jurassic (~172 to 161 Ma) ophiolite terrane in central California, extending over 700 km from Elder Creek at its northernmost segment extent to Point Sal at its southernmost terminus [2-5] (Figure 1). Petrologic and geochemical data indicate its formation in a supra-subduction zone (SSZ) fore-arc setting, probably above the east-dipping proto-Franciscan subduction zone [2, 6, 7]. Initiation of the subduction is considered to have possibly started along a large-offset transform fault zone, when an exotic or fringing is collided w
{"title":"Re−Os Isotope and PGE Abundance Systematics of Coast Range Ophiolite Peridotites and Chromitite, California: Insights into Fore-Arc Magmatic Processes","authors":"Sung Hi Choi, Samuel B. Mukasa, John W. Shervais, Igor S. Puchtel","doi":"10.2113/2024/lithosphere_2024_154","DOIUrl":"https://doi.org/10.2113/2024/lithosphere_2024_154","url":null,"abstract":"We report platinum-group element (PGE) and Re concentrations, and Re−Os isotopic data for peridotites and podiform chromitite from the mid-Jurassic Coast Range ophiolite (CRO), California. Our aim is to provide insights into the formation and evolution of the CRO in a fore-arc tectonic setting. The CRO peridotites are divided into two groups: abyssal and supra-subduction zone (SSZ). They have Ir-group PGE concentrations similar to estimates for the primitive mantle and nearly chondritic relative abundances [(Os/Ir)N ≈ 1.1]. Abyssal-type peridotites have slightly subchondritic Pd-group PGE (PPGE)−Re abundances and flat chondrite-normalized patterns, whereas the SSZ-type ones are depleted overall with highly fractionated PPGE−Re patterns. The CRO peridotites have 187Os/188Os values of 0.1188 to 0.1315 (γOs = −8.3 to 1.4) and 187Re/188Os ranging from 0.022 to 0.413. The oxygen fugacity based on the V/Yb ratios of the CRO peridotites is equivalent to the fayalite−magnetite−quartz buffer. The abyssal-type peridotites are residues after ≤5% melting of the primitive upper mantle and represent a remnant of oceanic lithosphere trapped in an SSZ setting but before it was re-melted or modified by subduction processes. The abyssal-type peridotites yield an aluminachron model age of ~1.5 Ga, implying that the CRO mantle had experienced episode(s) of melt extraction before the CRO crust was formed. The SSZ-type peridotites are refractory residues after ~5% to 15% melting. Extraction of fore-arc basalts generated mainly by decompression melting resulted in the SSZ-type peridotites. The chromitite has 187Os/188Os value of 0.1250 (γOs = −3.5) and PGE−Re patterns complementary to that of boninite, indicating a genetic link to fore-arc magmatism.Ophiolites are sections of the Earth’s oceanic crust and the underlying upper mantle that have been tectonically emplaced into continental margins, providing important insights into the processes of plate tectonics, the composition of the oceanic crust and mantle, and the dynamics of Earth’s interior. Ophiolites are also valuable as ore deposits hosting precious metals, including platinum-group elements (PGEs), ferrous metals (Cr, Mn, and Ti), and base metals (Co, Cu, and Ni). The oceanic crust preserved in ophiolites may form in any tectonic setting during the evolution of ocean basins, from the mid-ocean ridge to subduction initiation and final closure [1]. The Coast Range ophiolite (CRO) is a mid-Jurassic (~172 to 161 Ma) ophiolite terrane in central California, extending over 700 km from Elder Creek at its northernmost segment extent to Point Sal at its southernmost terminus [2-5] (Figure 1). Petrologic and geochemical data indicate its formation in a supra-subduction zone (SSZ) fore-arc setting, probably above the east-dipping proto-Franciscan subduction zone [2, 6, 7]. Initiation of the subduction is considered to have possibly started along a large-offset transform fault zone, when an exotic or fringing is collided w","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":"42 1","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141610898","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-19DOI: 10.2113/2024/lithosphere_2023_332
Wanda J. Taylor, Benjamin Surpless, Ilsa M. Schiefelbein Kerscher
Major normal fault systems are composed of segments that link as displacement accumulates, with linkage zone characteristics that reveal fault zone evolution. The steeply west-dipping Sevier fault zone in southwestern Utah, displays a complex fault network that developed between two long (>10 km), en echelon segments near the town of Orderville. Geologic map data and cross-sections of the transfer zone between the Mt. Carmel segment in the south and the Spencer Bench segment in the north reveal more than ten normal faults and four relay ramps displaying a range of geometries, including two relay ramps that display ramp-parallel folds. We suggest that transfer zone deformation was initially dominated by faults subparallel to the primary segments with later cross-faults that hard-linked these faults across most of the transfer zone. When the transfer zone was a soft-linked system, a displacement deficit likely existed relative to fault segments to the north and south. This early fault configuration would have reduced the efficiency of slip propagation associated with major earthquakes (>M7.0). In contrast, the present-day transfer zone, with a complex but hard-linked fault network, shows displacements that transition smoothly from the higher displacement (~800 m) southern segment to the lower displacement (~400 m) northern segment. That transition, combined with extensional strain within the zone, suggests that the Orderville fault network would be unlikely to impede propagation associated with future major earthquakes. The kinematic model of fault evolution presented here has implications for those investigating geothermal energy potential, groundwater flow, natural gas and oil reservoirs, mineral deposit formation, or seismic hazards.Over the past several decades, researchers have demonstrated that major normal fault systems are commonly segmented in map view and at depth, with segment linkage zone characteristics that can be used to reveal how long (10s–100s of km) fault zones evolve [1-10]. The interactions of fault segments at linkage zones perturb the local stress field, may permit slip transfer between fault segments, and can influence the formation of relay ramps, minor faults, and fracture networks [6, 11-13]. These fractures may promote fluid flow within a rock volume, so are important for evaluating oil and gas exploration, groundwater flow, and geothermal energy potential [13-17]. If heat flow is high enough, the intensely fractured damage zones associated with fault segment linkage [18] may be excellent targets for geothermal energy production [19-22]. Thus, a better understanding of fault network evolution and associated damage zone development will help future scientists more effectively target locations with high potential for geothermal energy production. In addition, because the entire length of long (from several km to over 100-km long) normal faults does not rupture during a single earthquake, linkage zones between segments play
{"title":"Complex Segment Linkage Along the Sevier Normal Fault, Southwestern Utah","authors":"Wanda J. Taylor, Benjamin Surpless, Ilsa M. Schiefelbein Kerscher","doi":"10.2113/2024/lithosphere_2023_332","DOIUrl":"https://doi.org/10.2113/2024/lithosphere_2023_332","url":null,"abstract":"Major normal fault systems are composed of segments that link as displacement accumulates, with linkage zone characteristics that reveal fault zone evolution. The steeply west-dipping Sevier fault zone in southwestern Utah, displays a complex fault network that developed between two long (>10 km), en echelon segments near the town of Orderville. Geologic map data and cross-sections of the transfer zone between the Mt. Carmel segment in the south and the Spencer Bench segment in the north reveal more than ten normal faults and four relay ramps displaying a range of geometries, including two relay ramps that display ramp-parallel folds. We suggest that transfer zone deformation was initially dominated by faults subparallel to the primary segments with later cross-faults that hard-linked these faults across most of the transfer zone. When the transfer zone was a soft-linked system, a displacement deficit likely existed relative to fault segments to the north and south. This early fault configuration would have reduced the efficiency of slip propagation associated with major earthquakes (>M7.0). In contrast, the present-day transfer zone, with a complex but hard-linked fault network, shows displacements that transition smoothly from the higher displacement (~800 m) southern segment to the lower displacement (~400 m) northern segment. That transition, combined with extensional strain within the zone, suggests that the Orderville fault network would be unlikely to impede propagation associated with future major earthquakes. The kinematic model of fault evolution presented here has implications for those investigating geothermal energy potential, groundwater flow, natural gas and oil reservoirs, mineral deposit formation, or seismic hazards.Over the past several decades, researchers have demonstrated that major normal fault systems are commonly segmented in map view and at depth, with segment linkage zone characteristics that can be used to reveal how long (10s–100s of km) fault zones evolve [1-10]. The interactions of fault segments at linkage zones perturb the local stress field, may permit slip transfer between fault segments, and can influence the formation of relay ramps, minor faults, and fracture networks [6, 11-13]. These fractures may promote fluid flow within a rock volume, so are important for evaluating oil and gas exploration, groundwater flow, and geothermal energy potential [13-17]. If heat flow is high enough, the intensely fractured damage zones associated with fault segment linkage [18] may be excellent targets for geothermal energy production [19-22]. Thus, a better understanding of fault network evolution and associated damage zone development will help future scientists more effectively target locations with high potential for geothermal energy production. In addition, because the entire length of long (from several km to over 100-km long) normal faults does not rupture during a single earthquake, linkage zones between segments play","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":"81 1","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141503521","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-30DOI: 10.2113/2024/lithosphere_2023_348
Ming Zou, Zheming Zhu, Weiting Gao, Tao Peng, Meng Wang
The Laoheba Phosphate Mine Area in the Sichuan Basin stands as one of China’s primary locations for phosphate extraction, boasting a diverse array of rock types and complex rock layers. In recent years, frequent geological disasters, notably landslides, have occurred in the mining area. The safe extraction of phosphate rock faces significant challenges, necessitating an in-depth exploration of the physical and mechanical properties of the rocks within the mining area. This study employs nuclear magnetic resonance (NMR) and X-ray diffractometer (XRD) testing on six typical rock specimens, contrasting and analyzing their physical traits, thus unveiling the impact of rock composition and microstructure on their mechanical properties. The MTS815 Flex Test GT rock mechanics testing system was employed to perform uniaxial compression, triaxial compression, Brazilian disk splitting, and triaxial penetration tests. The study systematically examined the mechanical characteristics of typical rocks in the mining area. The correctness of the experiments was mutually validated by four types of tests. Finally, an analysis of rock failure modes and patterns was conducted. Research suggests that phosphate ore exhibits the highest porosity and permeability. Phosphate ore exhibits significant development of original joints and cracks internally, along with numerous defects, leading to its minimal compressive and tensile strength. Phosphate ore is typically situated in regions of weakened rock mass strength. Real-time monitoring of confining pressure is essential during mining operations to prevent the collapse of surrounding rock formations. The findings of this study offer theoretical backing for secure mining operations in the Laoheba Mining Area of the Sichuan Basin while also furnishing fundamental physical and mechanical parameters for regional geomechanical analysis.The Sichuan Basin is situated in southwestern China. The mining area lies on the southwestern edge of the Sichuan Basin. The phosphate ore layer is found in the lower strata of the Cambrian System. The mining area boasts a diverse range of rock types. The rocks exhibit unique compositions. Their physical and mechanical features differ from those of ordinary rocks. We conducted research on six typical rocks selected from the mining area. Geological exploration and investigation into the physical and mechanical properties of rocks are essential prerequisites for the safe exploitation of phosphate mines.With the exploration and development of mineral resources, and the increasing scale of various underground rock engineering projects, higher demands have been placed on the design and construction of geotechnical engineering. In recent years, there has been a surge in accidents in rock engineering, drawing attention to the safety of underground rock engineering. The physical and mechanical properties of rocks are closely associated with the stability of rock engineering. Therefore, investigating thes
样品 4 出现严重故障，左侧出现一条斜穿透裂缝，右侧出现一条垂直裂缝，导致样品断裂成三块，两端严重受损。样品 5 出现复合破坏，上部出现两条垂直裂缝和一条横向裂缝。样品 P 有两条垂直的主要裂缝，其中一条在下部改变了方向，并向右延伸至底部。由于六种岩石的性质、成分和内部节理结构不同，岩石材料的物理和机械性能也各不相同。这导致了破坏模式和破坏过程中破碎程度的不同。在隧道施工过程中，应特别注意样本 4，因为它的抗压强度低、脆性明显、破碎程度高。此外，它在破坏过程中的变形相对较小，因此很难观察到，而且极有可能发生瞬间破坏。样本 4 属于围岩薄弱的区域，因此在采矿作业中必须加强位移监测。图 14 展示了巴西圆盘劈裂中六种岩石的断裂形态。由于这些岩石类型的物理和机械特性各不相同，圆盘劈裂的破坏模式也不尽相同。试样 1、2、4 和 5 表现出典型的巴西盘劈裂破坏模式。在加载过程中，主裂缝出现，横穿试样中心并贯穿整个试样。在受力端，应力集中导致局部碎裂，表现出明显的脆性。在试样 3 的失效过程中，围绕圆盘中心轴出现了两条对称的平行裂纹，将试样分为三部分。试样 3 中出现的这些裂纹可能源于试样内部预先存在的微裂纹，这些微裂纹在加载作用下进一步扩展，形成主裂纹。试样 P 显示了一条穿透试样的弯曲裂纹，但并未与试样中心相交。上部的裂纹表明是拉伸裂纹，而下部的斜裂纹则表明是剪切裂纹，从而形成了拉伸和剪切相结合的失效模式。图 15 显示了六种岩石在不同包络压力下的三轴压缩破坏模式。岩石样本的破坏形态复杂多样，破坏模式显示出明显的围压效应。在低围岩压力下，岩石样本会产生穿透性垂直裂缝和多条微裂缝，形成复杂的裂缝网络。在较高压力下，裂纹数量减少，复杂无序的裂纹网络逐渐转变为单一的剪切裂纹。概括老河坝矿区岩石的破坏行为和模式，在低围岩压力下，主要有两种破坏模式，即垂直劈裂破坏和共轭剪切破坏。随着围岩压力升高，出现了三种不同的破坏模式：局部剪切破坏、穿透剪切破坏和拉剪复合破坏。这五种破坏模式不仅随着围岩压力的变化而变化，而且还与岩性密切相关。表 8 列出了老河坝矿区岩石在不同围岩压力和岩性条件下的破坏模式。对这五种破坏模式的分析详述如下：垂直劈裂破坏（Ve-Sp）主要发生在低围岩压力（5 兆帕）下的岩石样本中。在这种压力下，岩石样本受到的横向约束极小，从而导致垂直裂缝的产生。这些裂缝表现为一条横穿整个岩样的主裂缝，同时伴有多条次裂缝，这些次裂缝在主裂缝附近分支，形成裂缝网络。共轭剪切破坏（Co-Sh）也主要发生在承受低包络压力（5 兆帕）的岩石样本中。在这些条件下，由于端面效应，样品最初会沿一侧断裂，导致轴向应力集中在另一侧，从而形成剪切裂缝。最终，对侧的这些裂纹汇聚成一个 V 形共轭主裂纹，导致样品失效。
{"title":"Analysis of Typical Rock Physical Characteristics, Mechanical Properties, and Failure Modes of the Laoheba Phosphate Mining Area in the Sichuan Basin, China","authors":"Ming Zou, Zheming Zhu, Weiting Gao, Tao Peng, Meng Wang","doi":"10.2113/2024/lithosphere_2023_348","DOIUrl":"https://doi.org/10.2113/2024/lithosphere_2023_348","url":null,"abstract":"The Laoheba Phosphate Mine Area in the Sichuan Basin stands as one of China’s primary locations for phosphate extraction, boasting a diverse array of rock types and complex rock layers. In recent years, frequent geological disasters, notably landslides, have occurred in the mining area. The safe extraction of phosphate rock faces significant challenges, necessitating an in-depth exploration of the physical and mechanical properties of the rocks within the mining area. This study employs nuclear magnetic resonance (NMR) and X-ray diffractometer (XRD) testing on six typical rock specimens, contrasting and analyzing their physical traits, thus unveiling the impact of rock composition and microstructure on their mechanical properties. The MTS815 Flex Test GT rock mechanics testing system was employed to perform uniaxial compression, triaxial compression, Brazilian disk splitting, and triaxial penetration tests. The study systematically examined the mechanical characteristics of typical rocks in the mining area. The correctness of the experiments was mutually validated by four types of tests. Finally, an analysis of rock failure modes and patterns was conducted. Research suggests that phosphate ore exhibits the highest porosity and permeability. Phosphate ore exhibits significant development of original joints and cracks internally, along with numerous defects, leading to its minimal compressive and tensile strength. Phosphate ore is typically situated in regions of weakened rock mass strength. Real-time monitoring of confining pressure is essential during mining operations to prevent the collapse of surrounding rock formations. The findings of this study offer theoretical backing for secure mining operations in the Laoheba Mining Area of the Sichuan Basin while also furnishing fundamental physical and mechanical parameters for regional geomechanical analysis.The Sichuan Basin is situated in southwestern China. The mining area lies on the southwestern edge of the Sichuan Basin. The phosphate ore layer is found in the lower strata of the Cambrian System. The mining area boasts a diverse range of rock types. The rocks exhibit unique compositions. Their physical and mechanical features differ from those of ordinary rocks. We conducted research on six typical rocks selected from the mining area. Geological exploration and investigation into the physical and mechanical properties of rocks are essential prerequisites for the safe exploitation of phosphate mines.With the exploration and development of mineral resources, and the increasing scale of various underground rock engineering projects, higher demands have been placed on the design and construction of geotechnical engineering. In recent years, there has been a surge in accidents in rock engineering, drawing attention to the safety of underground rock engineering. The physical and mechanical properties of rocks are closely associated with the stability of rock engineering. Therefore, investigating thes","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":"131 1","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140933153","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-30DOI: 10.2113/2024/lithosphere_2024_120
Xun Kang, Jingqiang Tan, Feng Lu, Ruipu Hu, Wenxuan Hu
Strontium isotopes of authigenic carbonate potentially record sediment provenance, fluid sources, and fluid–rock interactions, little was studied on this topic in clastic strata. This study investigated clastic rocks containing authigenic calcite in the Lower Triassic Baikouquan Formation in the Junggar Basin, northwestern China. Mineral compositional and fluid inclusion analyses were conducted to constrain the precipitation processes of authigenic calcite, and the Sr contents and isotope ratios of the calcite were also measured. The authigenic calcite was precipitated at 80–140°C as the final product of thermochemical oxidation of hydrocarbons and thus has high Mn contents and highly negative δ13CVPDB values (as low as −70‰). The calcite also exhibits anomalously low 87Sr/86Sr values (0.704827, 0.706612), which are lower than contemporaneous seawater and published 87Sr/86Sr values of carbonate cements in clastic sediments, and also much lower than 87Sr/86Sr values (0.722027, 0.736750) of alkali feldspar in the strata. These low 87Sr/86Sr values record the low 87Sr/86Sr of the dominant rocks in the provenance area, such as volcanic rocks. During diagenesis, especially mesodiagenesis, the charging of hydrocarbon-bearing fluids promoted abundant dissolution of orthoclase in the alkali feldspar detritus, releasing radiogenic 87Sr into the pore waters, and eventually increasing the 87Sr/86Sr values in the late-stage calcite that precipitated after this reaction. This inference is consistent with the positive correlation between the calcite 87Sr/86Sr ratios and the dissolution intensity of orthoclase. In regions that do not undergo hydrocarbon-charging and where orthoclase remains stable, the lower 87Sr/86Sr ratios of the calcite generally record the provenance. For authigenic calcite associated with intense fluid–rock interactions, the higher 87Sr/86Sr ratios reflect the enhanced dissolution intensity of 87Sr-rich minerals such as orthoclase. Therefore, combined with a petrological study, Sr isotopes of authigenic carbonate in clastic sediments can trace sediment provenance and intensity of fluid–rock interactions.Strontium isotope composition is a robust tracer of sediment provenance [1], fluid sources [2, 3], and fluid–rock reactions [4, 5]. The 87Sr/86Sr signature of ancient seawater can serve as a proxy for understanding the tectonic evolution of the Earth system [6, 7] as well as a tool for stratigraphic correlation [8-10]. The 87Sr/86Sr of seawater records the relative importance of two major strontium fluxes: (a) the riverine input of radiogenic Sr due to continental weathering and (b) the “mantle Sr” from hydrothermal circulation at mid-ocean ridges [1, 10]. Strontium isotopic composition of pore water mainly reflects fluctuations of fluid sources, pathways, mixing [2, 3], and fluid–rock reactions [4, 5]. Therefore, Sr isotope was also used in studies investigating the evolution of hydrology and paleohydrology [2, 11], diagenetic reactions, a
{"title":"Strontium Isotopic Variations of Authigenic Calcite in Clastic Strata Record Its Sediment Provenance and Fluid−Rock Interactions","authors":"Xun Kang, Jingqiang Tan, Feng Lu, Ruipu Hu, Wenxuan Hu","doi":"10.2113/2024/lithosphere_2024_120","DOIUrl":"https://doi.org/10.2113/2024/lithosphere_2024_120","url":null,"abstract":"Strontium isotopes of authigenic carbonate potentially record sediment provenance, fluid sources, and fluid–rock interactions, little was studied on this topic in clastic strata. This study investigated clastic rocks containing authigenic calcite in the Lower Triassic Baikouquan Formation in the Junggar Basin, northwestern China. Mineral compositional and fluid inclusion analyses were conducted to constrain the precipitation processes of authigenic calcite, and the Sr contents and isotope ratios of the calcite were also measured. The authigenic calcite was precipitated at 80–140°C as the final product of thermochemical oxidation of hydrocarbons and thus has high Mn contents and highly negative δ13CVPDB values (as low as −70‰). The calcite also exhibits anomalously low 87Sr/86Sr values (0.704827, 0.706612), which are lower than contemporaneous seawater and published 87Sr/86Sr values of carbonate cements in clastic sediments, and also much lower than 87Sr/86Sr values (0.722027, 0.736750) of alkali feldspar in the strata. These low 87Sr/86Sr values record the low 87Sr/86Sr of the dominant rocks in the provenance area, such as volcanic rocks. During diagenesis, especially mesodiagenesis, the charging of hydrocarbon-bearing fluids promoted abundant dissolution of orthoclase in the alkali feldspar detritus, releasing radiogenic 87Sr into the pore waters, and eventually increasing the 87Sr/86Sr values in the late-stage calcite that precipitated after this reaction. This inference is consistent with the positive correlation between the calcite 87Sr/86Sr ratios and the dissolution intensity of orthoclase. In regions that do not undergo hydrocarbon-charging and where orthoclase remains stable, the lower 87Sr/86Sr ratios of the calcite generally record the provenance. For authigenic calcite associated with intense fluid–rock interactions, the higher 87Sr/86Sr ratios reflect the enhanced dissolution intensity of 87Sr-rich minerals such as orthoclase. Therefore, combined with a petrological study, Sr isotopes of authigenic carbonate in clastic sediments can trace sediment provenance and intensity of fluid–rock interactions.Strontium isotope composition is a robust tracer of sediment provenance [1], fluid sources [2, 3], and fluid–rock reactions [4, 5]. The 87Sr/86Sr signature of ancient seawater can serve as a proxy for understanding the tectonic evolution of the Earth system [6, 7] as well as a tool for stratigraphic correlation [8-10]. The 87Sr/86Sr of seawater records the relative importance of two major strontium fluxes: (a) the riverine input of radiogenic Sr due to continental weathering and (b) the “mantle Sr” from hydrothermal circulation at mid-ocean ridges [1, 10]. Strontium isotopic composition of pore water mainly reflects fluctuations of fluid sources, pathways, mixing [2, 3], and fluid–rock reactions [4, 5]. Therefore, Sr isotope was also used in studies investigating the evolution of hydrology and paleohydrology [2, 11], diagenetic reactions, a","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":"142 1","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141503460","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-30DOI: 10.2113/2024/lithosphere_2023_324
Pengfei Zuo, Haihua Cheng, A. J. C. Magalhães, Jiangtao Sun, Liang Qiu, Zihan Xiao, Yiming Dong
Dolostone, with its complex diagenetic history, has long been debate. The formation of patchy dolostone, which consists of various types of dolomites, is particularly controversial due to the superimposed diagenetic events. In this study, we conducted mineralogical and stable isotope geochemical analyses of the Ediacaran patchy dolostone from the Dengying Formation in South Qinling to elucidate the diagenetic processes involved. Microscopic examination reveals that the patchy dolostone can be classified into three types: Type I, composed of micritic to powdery crystalline dolomite (D1) and fine crystalline dolomite (D2); Type II, primarily consisting of medium-coarse crystalline dolomite (D3) along with D2; and Type III, characterized by the presence of saddle dolomite (SD) and D1. Cathodoluminescence and electron probe microanalysis indicate that D2 and D3 are enriched in Mn and Fe, whereas SD is depleted in Sr and Na compared to D1. Backscattered electron images reveal a prevalence of apatite, particularly in Type III dolostone. Calcite and quartz extensively replace the dolomites. Carbon and oxygen isotopes indicate that D1 has the highest δ13C and δ18O values, while D2 and D3 show negative shifts, and SD exhibits the lowest values. These observations suggest that the transition from D1 to D2 and D3 is due to recrystallization processes during burial. The formation of SD is likely the result of hydrothermal activity. Consequently, the patchy dolostone experienced three main stages of diagenesis, which included the recrystallization of D1 and the formation of SD. Considering the vertical distribution of the patchy dolostone and the occurrence of hyperkarst breccia dolostone, it is reasonable to infer that sea level variations are the primary cause of the formation of patchy dolostone.The Ediacaran represents a pivotal era in Earth’s history, characterized by remarkable geological, oceanic, and biological changes [1, 2]. During this period, various types of dolostones were extensively developed [3]. Dolostone, which serves as a rock unit documenting the intricate history of sedimentation and diagenesis, has long been a subject of debate and extensive research in geology [4-8]. Various conceptual models, such as the evaporation pump, brine seepage reflux, mixed-water dolomitization, and hydrothermal dolomitization, have been proposed based on these investigations [9-16]. The development of thick dolostone is controlled by external factors, including the paleoclimate background, relative sea-level changes, and tectonic activity [17-20]. This is particularly significant when studying shallow-marine carbonate, where multiple occurrences of these factors may occur during penecontemporaneous or early burial periods, leading to various dolomitization processes. Patchy dolostone, a unique sedimentary fabric characterized by “patchy” sedimentary records and a complex diagenetic evolution [21-24], is controversial for hydrothermal genesis [25, 26] or earl
{"title":"Petrology and Stable Isotopes of Patchy Dolostone of Ediacaran Dengying Formation in South Qinling, Central China: Implication for the Diagenetic History","authors":"Pengfei Zuo, Haihua Cheng, A. J. C. Magalhães, Jiangtao Sun, Liang Qiu, Zihan Xiao, Yiming Dong","doi":"10.2113/2024/lithosphere_2023_324","DOIUrl":"https://doi.org/10.2113/2024/lithosphere_2023_324","url":null,"abstract":"Dolostone, with its complex diagenetic history, has long been debate. The formation of patchy dolostone, which consists of various types of dolomites, is particularly controversial due to the superimposed diagenetic events. In this study, we conducted mineralogical and stable isotope geochemical analyses of the Ediacaran patchy dolostone from the Dengying Formation in South Qinling to elucidate the diagenetic processes involved. Microscopic examination reveals that the patchy dolostone can be classified into three types: Type I, composed of micritic to powdery crystalline dolomite (D1) and fine crystalline dolomite (D2); Type II, primarily consisting of medium-coarse crystalline dolomite (D3) along with D2; and Type III, characterized by the presence of saddle dolomite (SD) and D1. Cathodoluminescence and electron probe microanalysis indicate that D2 and D3 are enriched in Mn and Fe, whereas SD is depleted in Sr and Na compared to D1. Backscattered electron images reveal a prevalence of apatite, particularly in Type III dolostone. Calcite and quartz extensively replace the dolomites. Carbon and oxygen isotopes indicate that D1 has the highest δ13C and δ18O values, while D2 and D3 show negative shifts, and SD exhibits the lowest values. These observations suggest that the transition from D1 to D2 and D3 is due to recrystallization processes during burial. The formation of SD is likely the result of hydrothermal activity. Consequently, the patchy dolostone experienced three main stages of diagenesis, which included the recrystallization of D1 and the formation of SD. Considering the vertical distribution of the patchy dolostone and the occurrence of hyperkarst breccia dolostone, it is reasonable to infer that sea level variations are the primary cause of the formation of patchy dolostone.The Ediacaran represents a pivotal era in Earth’s history, characterized by remarkable geological, oceanic, and biological changes [1, 2]. During this period, various types of dolostones were extensively developed [3]. Dolostone, which serves as a rock unit documenting the intricate history of sedimentation and diagenesis, has long been a subject of debate and extensive research in geology [4-8]. Various conceptual models, such as the evaporation pump, brine seepage reflux, mixed-water dolomitization, and hydrothermal dolomitization, have been proposed based on these investigations [9-16]. The development of thick dolostone is controlled by external factors, including the paleoclimate background, relative sea-level changes, and tectonic activity [17-20]. This is particularly significant when studying shallow-marine carbonate, where multiple occurrences of these factors may occur during penecontemporaneous or early burial periods, leading to various dolomitization processes. Patchy dolostone, a unique sedimentary fabric characterized by “patchy” sedimentary records and a complex diagenetic evolution [21-24], is controversial for hydrothermal genesis [25, 26] or earl","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":"25 1","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141503459","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Composite salt formation is a high-quality caprock for oil and gas resources. The accident encountered in composite salt formation drilling is a big problem to be solved in the drilling process. According to statistics, nearly 50% of drilling accidents occur in composite salt formations. The composite salt formation is mainly composed of salt, gypsum, and interbed mud, and the lithology is complex and changeable. Therefore, it is very important to study the deformation mechanism and leading influencing factors of composite salt formation in view of the problem of frequent accidents in the drilling process. In this article, the creep parameters based on the constitutive equation of creep of salt rock are obtained by combining theoretical with experimental research. A three-dimensional directional wellbore mechanical model is established to analyze the influence of inclination on borehole shrinkage.The salt gypsum layer refers to the formation with salt or gypsum as the main component. In the oil drilling industry, we usually regard the formation as mainly composed of sodium chloride or other water-soluble inorganic salts such as potassium chloride, magnesium chloride, calcium chloride, gypsum, or Glauber’s nitrate as the salt gypsum formation, that is, the salt gypsum layer. According to statistics, salt rocks in sedimentary basins are the best caprock, under which are buried a considerable amount of oil and gas resources in the world, especially rich unconventional oil and gas resources [1-3]. Therefore, the salt gypsum layer is not only the focus of the world oil industry but also the focus of our oil and gas resource development.Along with the process of oil and gas exploitation, the shallow, easily recoverable resources are gradually exhausted, and the exploitation center is gradually transferred to the deep oil and gas resources. The salt rock with very low permeability and porosity is the best caprock, and the drilling of salt rock is unavoidable in the drilling process. The gypsum rocks, which are mainly composed of salt or gypsum, exist above oil and gas reservoirs. The gypsum rocks found in our drilling are mainly distributed in Tarim, Jianghan, Sichuan, Shengli, Zhongyuan, North China, Xinjiang, Qinghai Changqing, and so forth. Various accidents occurred in the drilling of the gypsum rocks in the above oil fields, such as sticking and squeezing casing.Hambley et al. [4] improved the creep constitutive model of salt rock by fully combining the experimental and field data. Fossum et al. [5] determined the stress-related probability distribution function through the pure salt creep test and creep model. Weidinger et al. [6] established a composite plastic deformation model to explicitly consider the heterogeneity of the observed dislocation structure and calculated the transient creep and steady-state creep of salt rock with this model combined with the mechanical laws of dislocation motion. Urai et al. [7] discussed the process of dissolut
{"title":"Geomechanical Simulation of 3D Directional Borehole Circumference in Deep Composite Salt Formation","authors":"Shiyuan Li, Chenglong Li, Zhaowei Chen, Wenbao Zhai, Yajun Lei, Jiawei Cao","doi":"10.2113/2024/lithosphere_2023_212","DOIUrl":"https://doi.org/10.2113/2024/lithosphere_2023_212","url":null,"abstract":"Composite salt formation is a high-quality caprock for oil and gas resources. The accident encountered in composite salt formation drilling is a big problem to be solved in the drilling process. According to statistics, nearly 50% of drilling accidents occur in composite salt formations. The composite salt formation is mainly composed of salt, gypsum, and interbed mud, and the lithology is complex and changeable. Therefore, it is very important to study the deformation mechanism and leading influencing factors of composite salt formation in view of the problem of frequent accidents in the drilling process. In this article, the creep parameters based on the constitutive equation of creep of salt rock are obtained by combining theoretical with experimental research. A three-dimensional directional wellbore mechanical model is established to analyze the influence of inclination on borehole shrinkage.The salt gypsum layer refers to the formation with salt or gypsum as the main component. In the oil drilling industry, we usually regard the formation as mainly composed of sodium chloride or other water-soluble inorganic salts such as potassium chloride, magnesium chloride, calcium chloride, gypsum, or Glauber’s nitrate as the salt gypsum formation, that is, the salt gypsum layer. According to statistics, salt rocks in sedimentary basins are the best caprock, under which are buried a considerable amount of oil and gas resources in the world, especially rich unconventional oil and gas resources [1-3]. Therefore, the salt gypsum layer is not only the focus of the world oil industry but also the focus of our oil and gas resource development.Along with the process of oil and gas exploitation, the shallow, easily recoverable resources are gradually exhausted, and the exploitation center is gradually transferred to the deep oil and gas resources. The salt rock with very low permeability and porosity is the best caprock, and the drilling of salt rock is unavoidable in the drilling process. The gypsum rocks, which are mainly composed of salt or gypsum, exist above oil and gas reservoirs. The gypsum rocks found in our drilling are mainly distributed in Tarim, Jianghan, Sichuan, Shengli, Zhongyuan, North China, Xinjiang, Qinghai Changqing, and so forth. Various accidents occurred in the drilling of the gypsum rocks in the above oil fields, such as sticking and squeezing casing.Hambley et al. [4] improved the creep constitutive model of salt rock by fully combining the experimental and field data. Fossum et al. [5] determined the stress-related probability distribution function through the pure salt creep test and creep model. Weidinger et al. [6] established a composite plastic deformation model to explicitly consider the heterogeneity of the observed dislocation structure and calculated the transient creep and steady-state creep of salt rock with this model combined with the mechanical laws of dislocation motion. Urai et al. [7] discussed the process of dissolut","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":"118 1","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140888535","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-30DOI: 10.2113/2024/lithosphere_2023_306
Mikhail M. Buslov, Anna V. Kulikova, Evgenii V. Sklyarov, Alexei V. Travin
A model of tectonothermal evolution of the Zagan metamorphic core complex (MCC) based on the new data from 40Ar/39Ar dating of amphibole, mica, and apatite fission-track dating is discussed. A relationship with the long-range impact of processes from the collision of the North China (Amurian–North China) block with the Siberian continent in the Mesozoic era is proposed. The Zagan MСС was formed in the Cretaceous period on the southern flank of a high mountain uplift of Western Transbaikalia, composed of late Paleozoic granitoids of the Angara–Vitim batholith. According to 40Ar/39Ar dating of amphiboles and micas from the mylonite zone, the active development time of the Zagan MCC corresponds to the early Cretaceous epoch (131, 114 Ma). The tectonic exposure of the core from about 15 km to the depths of about 10 km occurred at a rate of tectonic erosion of 0.4–0.3 mm/year as a result of post-collisional extension of the Mongol–Okhotsk orogen. Apatite fission-track dating shows that further exhumation and cooling of the rocks to about 3 km occurred in the lower-upper Cretaceous epoch (112, 87 Ma). The erosional denudation rate was about 0.3 mm/year.MCC- metamorphic core complexes, AFT- apatite fission-trackMesozoic metamorphic core complexes (MCCs) [1-3] are common in East Asia. They mark global intracontinental extensions along the folded borders of the Siberian craton in Western Transbaikalia and the North China craton [4-13]. The Zagan MCC is one of the more than ten identified ones on the southern border of the Siberian Craton [6-13], where Paleozoic magmatic complexes of the world’s largest Baikal–Vitim and Khentei batholithes and well-known Cenozoic Baikal rift zone occur. Currently, the tectonothermal history of the rocks of the region using apatite fission track dating has been published in a small number of papers [14, 15], partly in [16-19]. In the papers [14, 15], the analysis of geological and geophysical data and the results of track dating revealed the evolution of the relief and tectonic stages of the region formation along the NE-SW profiles from the Baikal-Patom Upland to the Barguzin Ridge, located, respectively, in the northwest and northeast of Lake Baikal. It was assumed, that the Baikal-Patom Upland was reactivated in the middle Jurassic–early Cretaceous epoch after the Mongol-Okhotsk orogeny, occurred in the vast convergence zone of the North Chinese (Amurian–North China block) and Siberian cratons. Apatite fission track dating of the Barguzin Ridge (block) indicates [15] that it intensively rose (rapid cooling phase) in the period of 65–50 Ma (Pliocene-early Eocene epoch) and in the last five Ma (Pliocene-Quaternary period).Tectonothermal evolution of the late Paleozoic granitoids of the Angara–Vitim batholith has been reconstructed using complex thermochronology, including U/Pb, 40Ar/39Ar, and partly fission track dating methods [16-18]. Closure temperatures of the isotope systems of zircon and amphibole show that the rapid
{"title":"Mеsozoic Tectonothermal Evolution of the Zagan Metamorphic Core Complex in Western Transbaikalia: 40Ar/39Ar and FTA Dating","authors":"Mikhail M. Buslov, Anna V. Kulikova, Evgenii V. Sklyarov, Alexei V. Travin","doi":"10.2113/2024/lithosphere_2023_306","DOIUrl":"https://doi.org/10.2113/2024/lithosphere_2023_306","url":null,"abstract":"A model of tectonothermal evolution of the Zagan metamorphic core complex (MCC) based on the new data from 40Ar/39Ar dating of amphibole, mica, and apatite fission-track dating is discussed. A relationship with the long-range impact of processes from the collision of the North China (Amurian–North China) block with the Siberian continent in the Mesozoic era is proposed. The Zagan MСС was formed in the Cretaceous period on the southern flank of a high mountain uplift of Western Transbaikalia, composed of late Paleozoic granitoids of the Angara–Vitim batholith. According to 40Ar/39Ar dating of amphiboles and micas from the mylonite zone, the active development time of the Zagan MCC corresponds to the early Cretaceous epoch (131, 114 Ma). The tectonic exposure of the core from about 15 km to the depths of about 10 km occurred at a rate of tectonic erosion of 0.4–0.3 mm/year as a result of post-collisional extension of the Mongol–Okhotsk orogen. Apatite fission-track dating shows that further exhumation and cooling of the rocks to about 3 km occurred in the lower-upper Cretaceous epoch (112, 87 Ma). The erosional denudation rate was about 0.3 mm/year.MCC- metamorphic core complexes, AFT- apatite fission-trackMesozoic metamorphic core complexes (MCCs) [1-3] are common in East Asia. They mark global intracontinental extensions along the folded borders of the Siberian craton in Western Transbaikalia and the North China craton [4-13]. The Zagan MCC is one of the more than ten identified ones on the southern border of the Siberian Craton [6-13], where Paleozoic magmatic complexes of the world’s largest Baikal–Vitim and Khentei batholithes and well-known Cenozoic Baikal rift zone occur. Currently, the tectonothermal history of the rocks of the region using apatite fission track dating has been published in a small number of papers [14, 15], partly in [16-19]. In the papers [14, 15], the analysis of geological and geophysical data and the results of track dating revealed the evolution of the relief and tectonic stages of the region formation along the NE-SW profiles from the Baikal-Patom Upland to the Barguzin Ridge, located, respectively, in the northwest and northeast of Lake Baikal. It was assumed, that the Baikal-Patom Upland was reactivated in the middle Jurassic–early Cretaceous epoch after the Mongol-Okhotsk orogeny, occurred in the vast convergence zone of the North Chinese (Amurian–North China block) and Siberian cratons. Apatite fission track dating of the Barguzin Ridge (block) indicates [15] that it intensively rose (rapid cooling phase) in the period of 65–50 Ma (Pliocene-early Eocene epoch) and in the last five Ma (Pliocene-Quaternary period).Tectonothermal evolution of the late Paleozoic granitoids of the Angara–Vitim batholith has been reconstructed using complex thermochronology, including U/Pb, 40Ar/39Ar, and partly fission track dating methods [16-18]. Closure temperatures of the isotope systems of zircon and amphibole show that the rapid","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":"4 1","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141190281","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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