Lop Nur is located at the eastmost end of the Tarim Basin in Xinjiang, Northwestern China. This study reviews the hydrochemical characteristics and evolution of underground brine in Lop Nur, based on analytical data from 429 water samples (mainly brine). It is found that in the NE–SW direction, from the periphery to the Luobei sub-depression, while the hydrochemical type varies from the sodium sulfate subtype (S) to the magnesium sulfate subtype (M), the corresponding brine in the phase diagram transfers from the thenardite phase (Then) area, through the bloedite phase (Blo), epsomite phase (Eps), picromerite phase (Picro), finally reaching the sylvite phase (Syl) area. As for the degree of evolution, the sequence is the periphery < Luobei horizontally and the overlying glauberite brine < the underlying clastic brine vertically. It is concluded that the oxygen and hydrogen isotopic compositions of the brine have evidently been affected through the effects of evaporation and altitude, as well as the changes in local water circulation in recent years. Boron and chloride isotopic compositions show that the glauberite brine is formed under more arid conditions than the clastic one. The strontium isotopic composition indicates that the Lop Nur brine primarily originates from surface water; however, deep recharge may also be involved in the evolution of the brine, according to previous noble gas studies. It is confirmed that the brine in Lop Nur has become enriched with potassium prior to halite precipitation over the full course of the salt lake's evolution. Based on chemical compositions of brine from drillhole LDK01 and previous lithological studies, the evolution of the salt lake can be divided into three stages and it is inferred that the brine in Lop Nur may have undergone at least two significant concentration-dilution periods.
{"title":"Hydrochemical Characteristics and Evolution of Underground Brine in Lop Nur, Northwestern China","authors":"Ying BO, Chenglin LIU, Pengcheng JIAO, Fenglin LÜ, Hua ZHANG","doi":"10.1111/1755-6724.15127","DOIUrl":"10.1111/1755-6724.15127","url":null,"abstract":"<p>Lop Nur is located at the eastmost end of the Tarim Basin in Xinjiang, Northwestern China. This study reviews the hydrochemical characteristics and evolution of underground brine in Lop Nur, based on analytical data from 429 water samples (mainly brine). It is found that in the NE–SW direction, from the periphery to the Luobei sub-depression, while the hydrochemical type varies from the sodium sulfate subtype (S) to the magnesium sulfate subtype (M), the corresponding brine in the phase diagram transfers from the thenardite phase (Then) area, through the bloedite phase (Blo), epsomite phase (Eps), picromerite phase (Picro), finally reaching the sylvite phase (Syl) area. As for the degree of evolution, the sequence is the periphery < Luobei horizontally and the overlying glauberite brine < the underlying clastic brine vertically. It is concluded that the oxygen and hydrogen isotopic compositions of the brine have evidently been affected through the effects of evaporation and altitude, as well as the changes in local water circulation in recent years. Boron and chloride isotopic compositions show that the glauberite brine is formed under more arid conditions than the clastic one. The strontium isotopic composition indicates that the Lop Nur brine primarily originates from surface water; however, deep recharge may also be involved in the evolution of the brine, according to previous noble gas studies. It is confirmed that the brine in Lop Nur has become enriched with potassium prior to halite precipitation over the full course of the salt lake's evolution. Based on chemical compositions of brine from drillhole LDK01 and previous lithological studies, the evolution of the salt lake can be divided into three stages and it is inferred that the brine in Lop Nur may have undergone at least two significant concentration-dilution periods.</p>","PeriodicalId":7095,"journal":{"name":"Acta Geologica Sinica ‐ English Edition","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2023-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136232776","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
It is well established that Cretaceous magmatism in the South China Block (SCB) is related to the Paleo-Pacific subduction. However, the starting time and the associated deep crust-mantle processes are still debatable. Mafic dike swarms carry important information on the deep earth (including mantle) geodynamics and geochemical evolution. In the Jiangnan Orogen (South China), there is no information on whether the Mesozoic magmatic activities in this region are also directly related to the Pacific subduction or not. In this study, we present detailed zircon U-Pb geochronological, whole-rock element and Sr-Nd isotope data for Early Cretaceous Tuanshanbei dolerite dikes, and provide new constraints on the condition of the lithospheric mantle and mantle dynamics of the SCB during that time. LA-ICP-MS zircon U-Pb dating suggests that this dolerite erupted in the Early Cretaceous (∼145 Ma). All samples have alkaline geochemical affinities with K2O + Na2O = 3.11–4.04 wt%, K2O/Na2O = 0.50–0.72, and Mg# = 62.24–65.13. They are enriched in LILE but depleted in HFSE with higher initial 87Sr/86Sr ratio (0.706896–0.714743) and lower εNd(t) (–2.61 to –1.67). They have high Nb/U, Nb/La, La/Sm and Rb/Sr, and low La/Nb, La/Ta, Ce/Pb, Ba/Rb, Tb/Yb and Gd/Yb ratios. Such geochemical signatures suggest that the fractional crystallization is obvious but crustal contamination play a negligible role during magmatic evolution. Tuanshanbei dolerite were most likely derived from low-degree (2%–5%) partial melting of a phlogopite-bearing mantle material consisted of ∼85% spinel peridotite and ∼15% garnet peridotite previously metasomatized by asthenosphere-derived fluids/melts with minor subduction-derived fluids/melts. Slab-rollback generally lead to the upwelling of the hot asthenosphere. The upwelling of asthenosphere consuming the lithospheric mantle by thermo-mechanical-chemical erosion. The lithospheric mantle may have partially melted due to the heating by the upwelling asthenosphere and lithospheric extension. It is inferred that the Tuanshanbei dolerite might be associated with the initial slab rollback and corresponding lithospheric extension occurred potentially at ca. 145 Ma.
{"title":"Early Cretaceous Metasomatized Lithospheric Mantle beneath the Central Jiangnan Orogen in South China: Geochemical and Sr-Nd Isotope Evidence from the Tuanshanbei Dolerite","authors":"Cheng WANG, Hantao WEI, Qingquan LIU, Zhao YANG","doi":"10.1111/1755-6724.15129","DOIUrl":"10.1111/1755-6724.15129","url":null,"abstract":"<p>It is well established that Cretaceous magmatism in the South China Block (SCB) is related to the Paleo-Pacific subduction. However, the starting time and the associated deep crust-mantle processes are still debatable. Mafic dike swarms carry important information on the deep earth (including mantle) geodynamics and geochemical evolution. In the Jiangnan Orogen (South China), there is no information on whether the Mesozoic magmatic activities in this region are also directly related to the Pacific subduction or not. In this study, we present detailed zircon U-Pb geochronological, whole-rock element and Sr-Nd isotope data for Early Cretaceous Tuanshanbei dolerite dikes, and provide new constraints on the condition of the lithospheric mantle and mantle dynamics of the SCB during that time. LA-ICP-MS zircon U-Pb dating suggests that this dolerite erupted in the Early Cretaceous (∼145 Ma). All samples have alkaline geochemical affinities with K<sub>2</sub>O + Na<sub>2</sub>O = 3.11–4.04 wt%, K<sub>2</sub>O/Na<sub>2</sub>O = 0.50–0.72, and Mg<sup>#</sup> = 62.24–65.13. They are enriched in LILE but depleted in HFSE with higher initial <sup>87</sup>Sr/<sup>86</sup>Sr ratio (0.706896–0.714743) and lower <i>ε</i><sub>Nd</sub>(<i>t</i>) (–2.61 to –1.67). They have high Nb/U, Nb/La, La/Sm and Rb/Sr, and low La/Nb, La/Ta, Ce/Pb, Ba/Rb, Tb/Yb and Gd/Yb ratios. Such geochemical signatures suggest that the fractional crystallization is obvious but crustal contamination play a negligible role during magmatic evolution. Tuanshanbei dolerite were most likely derived from low-degree (2%–5%) partial melting of a phlogopite-bearing mantle material consisted of ∼85% spinel peridotite and ∼15% garnet peridotite previously metasomatized by asthenosphere-derived fluids/melts with minor subduction-derived fluids/melts. Slab-rollback generally lead to the upwelling of the hot asthenosphere. The upwelling of asthenosphere consuming the lithospheric mantle by thermo-mechanical-chemical erosion. The lithospheric mantle may have partially melted due to the heating by the upwelling asthenosphere and lithospheric extension. It is inferred that the Tuanshanbei dolerite might be associated with the initial slab rollback and corresponding lithospheric extension occurred potentially at ca. 145 Ma.</p>","PeriodicalId":7095,"journal":{"name":"Acta Geologica Sinica ‐ English Edition","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2023-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136233696","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Shenxianshui granites in the western Gejiu area were formed in the Late Cretaceous. Laser ablation inductively coupled plasma mass spectrometry indicates zircon U-Pb ages ranging from 90.67 ± 0.7 to 85.97 ± 0.6 Ma. The intrusive rocks are peraluminous (A/CNK = 1.03 to 1.33) and calc-alkaline, showing an affinity towards I-type granite. Large ion lithophilic elements are enriched in K and Rb, while high field strength elements are depleted. Moreover, light rare earth elements are significantly enriched, showing a slight negative Eu anomaly (Eu/Eu* = 0.39 to 0.58). Shenxianshui granite has a relatively high initial Sr isotope ratio (87Sr/86Sr)i (0.7098–0.7105), negative εNd(t) values (−7.99 to −7.44) and negative εHf(t) values (−8.37 to −2.58). Combined with previous studies, these characteristics suggest that the Shenxianshui alkaline granites were formed in a post-collision extensional environment. The alkaline granitic magma possibly originated from the partial melting of the lower crust during the Mesoproterozoic era and may have contained mantle source materials. Shenxianshui alkaline granite was formed from mixed magma with a high degree of crystal differentiation. The abundance of ore-forming elements indicates that Shenxianshui granite has the potential to mineralize key metals and rare earth elements.
地九西部的神仙水花岗岩形成于晚白垩世。激光烧蚀电感耦合等离子体质谱法显示锆石U-Pb年龄为90.67 ± 0.7至85.97 ± 0.6 Ma。侵入岩为过铝质(A/CNK = 1.03 至 1.33)和钙碱性,显示出与 I 型花岗岩的亲缘关系。大离子亲岩元素中富含 K 和 Rb,而高场强元素则贫乏。此外,轻稀土元素明显富集,显示出轻微的负 Eu 异常(Eu/Eu* = 0.39 至 0.58)。神仙水花岗岩具有相对较高的初始 Sr 同位素比(87Sr/86Sr)i (0.7098-0.7105)、负的 εNd(t)值(-7.99 至 -7.44)和负的 εHf(t)值(-8.37 至 -2.58)。结合以往的研究,这些特征表明神仙水碱性花岗岩是在碰撞后延伸环境中形成的。碱性花岗岩岩浆可能来源于中新生代下地壳的部分熔融,也可能含有地幔源物质。神仙水碱性花岗岩由晶体分异程度较高的混合岩浆形成。丰富的成矿元素表明,神仙水花岗岩具有主要金属和稀土元素的成矿潜力。
{"title":"Petrogenesis and Tectonic Significance of Shenxianshui Alkaline Granite in Gejiu, Yunnan Province, China","authors":"Rong YANG, Yongqing CHEN","doi":"10.1111/1755-6724.15124","DOIUrl":"10.1111/1755-6724.15124","url":null,"abstract":"<p>The Shenxianshui granites in the western Gejiu area were formed in the Late Cretaceous. Laser ablation inductively coupled plasma mass spectrometry indicates zircon U-Pb ages ranging from 90.67 ± 0.7 to 85.97 ± 0.6 Ma. The intrusive rocks are peraluminous (A/CNK = 1.03 to 1.33) and calc-alkaline, showing an affinity towards I-type granite. Large ion lithophilic elements are enriched in K and Rb, while high field strength elements are depleted. Moreover, light rare earth elements are significantly enriched, showing a slight negative Eu anomaly (Eu/Eu* = 0.39 to 0.58). Shenxianshui granite has a relatively high initial Sr isotope ratio (<sup>87</sup>Sr/<sup>86</sup>Sr)<sub>i</sub> (0.7098–0.7105), negative <i>ε</i><sub>Nd</sub>(<i>t</i>) values (−7.99 to −7.44) and negative <i>ε</i><sub>Hf</sub>(<i>t</i>) values (−8.37 to −2.58). Combined with previous studies, these characteristics suggest that the Shenxianshui alkaline granites were formed in a post-collision extensional environment. The alkaline granitic magma possibly originated from the partial melting of the lower crust during the Mesoproterozoic era and may have contained mantle source materials. Shenxianshui alkaline granite was formed from mixed magma with a high degree of crystal differentiation. The abundance of ore-forming elements indicates that Shenxianshui granite has the potential to mineralize key metals and rare earth elements.</p>","PeriodicalId":7095,"journal":{"name":"Acta Geologica Sinica ‐ English Edition","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2023-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136158790","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A polymetallic layer is usually developed at the bottom of the early Cambrian black shale in Guizhou Province. The mineral that makes up the polymetallic layer is related to the sedimentary facies. To analyze the differentiation mechanism between polymetallic deposits (Ni-Mo and V), the Zhijin Gezhongwu profile located in the outer shelf and the Sansui Haishan V deposit located in the lower slope are selected to study the in situ sulfur isotopes and trace elements of pyrite. The results show that δ34S values of pyrite vary widely from −7.8 ‰ to 28 ‰ in the Gezhongwu profile, while the δ34S values are relatively uniform (from 27.8 ‰ to 38.4 ‰) in the Haishan profile. The isotopic S composition is consistent with the transition that occurs in the sedimentary phase from the shelf to the deep sea on the transgressive Yangtze platform; this indicates that the δ34SO42– values in seawater must be differently distributed in depositional environments. The sulfur in the Ni-Mo layer is produced after the mixing of seawater and hydrothermal fluid, while the V layer mainly originates from seawater. Overall, the Ni-Mo and V deposits have been differentiated primarily on the basis of the combined effect of continental weathering and hydrothermal fluid.
贵州省早寒武世黑色页岩底部通常发育有多金属层。构成多金属层的矿物与沉积面有关。为分析多金属矿床(镍钼矿和V型矿)之间的分异机制,选取了位于外陆架的织金革中坞剖面和位于下斜的三穗海山V型矿床,对黄铁矿的原位硫同位素和微量元素进行了研究。结果表明,葛忠武剖面黄铁矿的δ34S值变化较大,从-7.8‰到28‰,而海山剖面的δ34S值相对均匀(从27.8‰到38.4‰)。这种同位素 S 组成与横断长江地台沉积相从陆架向深海的过渡相吻合;这表明海水中的δ34SO42-值在沉积环境中的分布一定是不同的。镍钼层中的硫是海水与热液混合后产生的,而V层中的硫主要来源于海水。总体而言,镍-钼矿床和 V 矿床主要是根据大陆风化和热液的共同作用来区分的。
{"title":"Sedimentary Environment and Mineralization of the Black Shale Polymetallic Layer in the Early Cambrian, SW China: Constraints from in situ LA-ICP-MS Analysis of Pyrite","authors":"Zhen YANG, Yong FU, Chao LI, Xi CAI, Chuan GUO","doi":"10.1111/1755-6724.15126","DOIUrl":"10.1111/1755-6724.15126","url":null,"abstract":"<p>A polymetallic layer is usually developed at the bottom of the early Cambrian black shale in Guizhou Province. The mineral that makes up the polymetallic layer is related to the sedimentary facies. To analyze the differentiation mechanism between polymetallic deposits (Ni-Mo and V), the Zhijin Gezhongwu profile located in the outer shelf and the Sansui Haishan V deposit located in the lower slope are selected to study the in situ sulfur isotopes and trace elements of pyrite. The results show that <i>δ</i><sup>34</sup>S values of pyrite vary widely from −7.8 ‰ to 28 ‰ in the Gezhongwu profile, while the <i>δ</i><sup>34</sup>S values are relatively uniform (from 27.8 ‰ to 38.4 ‰) in the Haishan profile. The isotopic S composition is consistent with the transition that occurs in the sedimentary phase from the shelf to the deep sea on the transgressive Yangtze platform; this indicates that the <i>δ</i><sup>34</sup>SO<sub>4</sub><sup>2–</sup> values in seawater must be differently distributed in depositional environments. The sulfur in the Ni-Mo layer is produced after the mixing of seawater and hydrothermal fluid, while the V layer mainly originates from seawater. Overall, the Ni-Mo and V deposits have been differentiated primarily on the basis of the combined effect of continental weathering and hydrothermal fluid.</p>","PeriodicalId":7095,"journal":{"name":"Acta Geologica Sinica ‐ English Edition","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2023-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136160004","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yipeng FENG, Genhou WANG, Shulai WANG, Dian LI, Huan WANG, Yang LU, Han LIU, Peilie ZHANG
The Jitang metamorphic complex is key to studying the tectonic evolution of the Northern Lancangjiang zone. Through structural-lithological mapping, structural analysis and laboratory testing, the composition of the Jitang metamorphic complex was determined. The macro- and microstructural analyses of the ductile detachment shear zone (Guoxuepu ductile shear zone, 2–4 km wide) between the metamorphic complex and the overlying sedimentary cap show that the shear sense of the ductile shear zones is top-to-the-southeast. The presence of various deformation features and quartz C-axis electron backscatter diffraction (EBSD) fabric analysis suggests multiple deformation events occurring at different temperatures. The average stress is 25.68 MPa, with the strain rates (έ) ranging from 9.77×10–14 s–1 to 6.52×10–16 s-1. The finite strain of the Guoxuepu ductile shear zone indicates an elongated strain pattern. The average kinematic vorticity of the Guoxuepu ductile shear zone is 0.88, implying that the shear zone is dominated by simple shear. The muscovite selected from the protomylonite samples in the Guoxuepu ductile shear zone yields a 40Ar-39Ar age of 60.09 ± 0.38 Ma. It is suggested that, coeval with the initial Indo–Eurasian collision, the development of strike-slip faults led to a weak and unstable crust, upwelling of lower crust magma, then induced the detachment of the Jitang metamorphic complex in the Eocene.
{"title":"Structural, 40Ar/39Ar Geochronological and Rheological Feature Analysis of the Guoxuepu Shear Zone: Indications for the Jitang Metamorphic Complex in the Northern Lancangjiang Zone","authors":"Yipeng FENG, Genhou WANG, Shulai WANG, Dian LI, Huan WANG, Yang LU, Han LIU, Peilie ZHANG","doi":"10.1111/1755-6724.15119","DOIUrl":"10.1111/1755-6724.15119","url":null,"abstract":"<p>The Jitang metamorphic complex is key to studying the tectonic evolution of the Northern Lancangjiang zone. Through structural-lithological mapping, structural analysis and laboratory testing, the composition of the Jitang metamorphic complex was determined. The macro- and microstructural analyses of the ductile detachment shear zone (Guoxuepu ductile shear zone, 2–4 km wide) between the metamorphic complex and the overlying sedimentary cap show that the shear sense of the ductile shear zones is top-to-the-southeast. The presence of various deformation features and quartz C-axis electron backscatter diffraction (EBSD) fabric analysis suggests multiple deformation events occurring at different temperatures. The average stress is 25.68 MPa, with the strain rates (έ) ranging from 9.77×10<sup>–14</sup> s<sup>–1</sup> to 6.52×10<sup>–16</sup> s<sup>-1</sup>. The finite strain of the Guoxuepu ductile shear zone indicates an elongated strain pattern. The average kinematic vorticity of the Guoxuepu ductile shear zone is 0.88, implying that the shear zone is dominated by simple shear. The muscovite selected from the protomylonite samples in the Guoxuepu ductile shear zone yields a <sup>40</sup>Ar-<sup>39</sup>Ar age of 60.09 ± 0.38 Ma. It is suggested that, coeval with the initial Indo–Eurasian collision, the development of strike-slip faults led to a weak and unstable crust, upwelling of lower crust magma, then induced the detachment of the Jitang metamorphic complex in the Eocene.</p>","PeriodicalId":7095,"journal":{"name":"Acta Geologica Sinica ‐ English Edition","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2023-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136159406","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Nuri deposit is the only Cu-W-Mo polymetallic deposit with large-scale WO3 resources in the eastern section of the Gangdese metallogenic belt, Tibet, China. However, the genetic type of this deposit has been controversial since its discovery. Based on a study of the geological characteristics of the deposit, this study presents mineralization stages, focusing on the oxide stage and the quartz-sulfide stage where scheelite is mainly formed, referred to as Sch-A and Sch-B, respectively. Through LA-ICP-MS trace element and Sr isotope analyses, the origin, evolutionary process of the ore-forming fluid and genesis of the ore deposit are investigated. Scanning Electron Microscope-Cathodoluminescence (SEM-CL) observations reveal that Sch-A consists of three generations, with dark gray homogenous Sch-A1 being replaced by relatively lighter and homogeneous Sch-A2 and Sch-A3, with Sch-A2 displaying a gray CL image color with vague and uneven growth bands and Sch-A3 has a light gray CL image color with hardly any growth band. In contrast, Sch-B exhibits a ‘core-rim’ structure, with the core part (Sch-B1) being dark gray and displaying a uniform growth band, while the rim part (Sch-B2) is light gray and homogeneous. The normalized distribution pattern of rare earth elements in scheelite and Sr isotope data suggest that the early ore-forming fluid in the Nuri deposit originated from granodiorite porphyry and, later on, some country rock material was mixed in, due to strong water-rock interaction. Combining the O-H isotope data further indicates that the ore-forming fluid in the Nuri deposit originated from magmatic-hydrothermal sources, with contributions from metamorphic water caused by water-rock interaction during the mineralization process, as well as later meteoric water. The intense water-rock interaction likely played a crucial role in the precipitation of scheelite, leading to varying Eu anomalies in different generations of scheelite from the oxide stage to the quartz-sulfide stage, while also causing a gradual decrease in oxygen fugacity (fO2) and a slow rise in pH value. Additionally, the high Mo and low Sr contents in the scheelite are consistent with typical characteristics of magmatic-hydrothermal scheelite. Therefore, considering the geological features of the deposit, the geochemical characteristics of scheelite and the O-H isotope data published previously, it can be concluded that the genesis of the Nuri deposit belongs to porphyry-skarn deposit.
{"title":"Genesis of the Nuri Cu-W-Mo Deposit, Tibet, China: Constraints from in situ Trace Elements and Sr Isotopic Analysis of Scheelite","authors":"Yiyun WANG, Zhishan WU, Wenqing CHEN, Qing'an DU, Liwei TANG, Hongzhao SHI, Guotao MA, Zhi ZHANG, Wei LIANG, Bo WU, Hengyi MIAO","doi":"10.1111/1755-6724.15120","DOIUrl":"10.1111/1755-6724.15120","url":null,"abstract":"<p>The Nuri deposit is the only Cu-W-Mo polymetallic deposit with large-scale WO<sub>3</sub> resources in the eastern section of the Gangdese metallogenic belt, Tibet, China. However, the genetic type of this deposit has been controversial since its discovery. Based on a study of the geological characteristics of the deposit, this study presents mineralization stages, focusing on the oxide stage and the quartz-sulfide stage where scheelite is mainly formed, referred to as Sch-A and Sch-B, respectively. Through LA-ICP-MS trace element and Sr isotope analyses, the origin, evolutionary process of the ore-forming fluid and genesis of the ore deposit are investigated. Scanning Electron Microscope-Cathodoluminescence (SEM-CL) observations reveal that Sch-A consists of three generations, with dark gray homogenous Sch-A1 being replaced by relatively lighter and homogeneous Sch-A2 and Sch-A3, with Sch-A2 displaying a gray CL image color with vague and uneven growth bands and Sch-A3 has a light gray CL image color with hardly any growth band. In contrast, Sch-B exhibits a ‘core-rim’ structure, with the core part (Sch-B1) being dark gray and displaying a uniform growth band, while the rim part (Sch-B2) is light gray and homogeneous. The normalized distribution pattern of rare earth elements in scheelite and Sr isotope data suggest that the early ore-forming fluid in the Nuri deposit originated from granodiorite porphyry and, later on, some country rock material was mixed in, due to strong water-rock interaction. Combining the O-H isotope data further indicates that the ore-forming fluid in the Nuri deposit originated from magmatic-hydrothermal sources, with contributions from metamorphic water caused by water-rock interaction during the mineralization process, as well as later meteoric water. The intense water-rock interaction likely played a crucial role in the precipitation of scheelite, leading to varying Eu anomalies in different generations of scheelite from the oxide stage to the quartz-sulfide stage, while also causing a gradual decrease in oxygen fugacity (<i>f</i>O<sub>2</sub>) and a slow rise in pH value. Additionally, the high Mo and low Sr contents in the scheelite are consistent with typical characteristics of magmatic-hydrothermal scheelite. Therefore, considering the geological features of the deposit, the geochemical characteristics of scheelite and the O-H isotope data published previously, it can be concluded that the genesis of the Nuri deposit belongs to porphyry-skarn deposit.</p>","PeriodicalId":7095,"journal":{"name":"Acta Geologica Sinica ‐ English Edition","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2023-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136159412","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract The Lower Cretaceous Manville Group of Upper McMurray Formation is one of the main bitumen reservoirs in Athabasca. In this study, the relationship between reservoirs heterogeneity and bitumen geochemical characteristics were analyzed through core and microscopic observation, lab analysis, petrophysics and logging data. Based on the sedimentology framework, the formation environment of high‐quality oil sand reservoirs and their significance for development were discussed. The results indicate that four types lithofacies were recognized in the Upper McMurray Formation based on their depositional characteristics. Each lithofacies reservoirs has unique physical properties, and is subject to varying degrees of degradation, resulting in diversity of bitumen content and geochemical composition. The tidal bar (TB) or tidal channel (TC) facies reservoir have excellent physical properties, which are evaluated as gas or water intervals due to strong degradation. The reservoir of sand bar (SB) facies was evaluated as oil intervals, due to its poor physical properties and weak degradation. The reservoir of mixed flat (MF) facies is composed of sand intercalated with laminated shale, which is evaluated as poor oil intervals due to its poor connectivity. The shale content in oil sand reservoir is very important for the reservoir physical properties and bitumen degradation degree. In the context of regional biodegradation, oil sand reservoirs with good physical properties will suffer from strong degradation, while oil sand reservoirs with relatively poor physical properties are more conducive to the bitumen preservation.
{"title":"Impact of Reservoir Heterogeneity on Bitumen Content in Mackay River Oil Sands, Athabasca (Canada)","authors":"Xiaofa YANG, Diyun YU, Suwei WU, Junhao REN, Dingsheng CHENG, Jixin HUANG, Chengyu YANG, Guoqing MA, Meijun LI","doi":"10.1111/1755-6724.15123","DOIUrl":"https://doi.org/10.1111/1755-6724.15123","url":null,"abstract":"Abstract The Lower Cretaceous Manville Group of Upper McMurray Formation is one of the main bitumen reservoirs in Athabasca. In this study, the relationship between reservoirs heterogeneity and bitumen geochemical characteristics were analyzed through core and microscopic observation, lab analysis, petrophysics and logging data. Based on the sedimentology framework, the formation environment of high‐quality oil sand reservoirs and their significance for development were discussed. The results indicate that four types lithofacies were recognized in the Upper McMurray Formation based on their depositional characteristics. Each lithofacies reservoirs has unique physical properties, and is subject to varying degrees of degradation, resulting in diversity of bitumen content and geochemical composition. The tidal bar (TB) or tidal channel (TC) facies reservoir have excellent physical properties, which are evaluated as gas or water intervals due to strong degradation. The reservoir of sand bar (SB) facies was evaluated as oil intervals, due to its poor physical properties and weak degradation. The reservoir of mixed flat (MF) facies is composed of sand intercalated with laminated shale, which is evaluated as poor oil intervals due to its poor connectivity. The shale content in oil sand reservoir is very important for the reservoir physical properties and bitumen degradation degree. In the context of regional biodegradation, oil sand reservoirs with good physical properties will suffer from strong degradation, while oil sand reservoirs with relatively poor physical properties are more conducive to the bitumen preservation.","PeriodicalId":7095,"journal":{"name":"Acta Geologica Sinica ‐ English Edition","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136158785","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jianchao SU, Xu LIN, Chang'an LI, Jolivet MARC, Lin WU, Feng CHENG, Bin DENG, Zhonghai WU, Xiaokang CHEN, Chengwei HU
Plate subduction leads to complex exhumation processes on continents. The Huangling Massif lies at the northern margin of the South China Block. Whether the Huangling Massif was exhumed as a watershed of the middle reaches of the Paleo-Yangtze River during the Mesozoic remains under debate. We examined the exhumation history of the Huangling Massif based on six granite bedrock samples, using apatite fission track (AFT) and apatite and zircon (U-Th)/He (AHe and ZHe) thermochronology. These samples yielded ages of 157–132 Ma (ZHe), 119–106 Ma (AFT), and 114–72 Ma (AHe), respectively. Thermal modeling revealed that three phases of rapid cooling occurred during the Late Jurassic–Early Cretaceous, late Early Cretaceous, and Late Cretaceous. These exhumation processes led to the high topographic relief responsible for the emergence of the Huangling Massif. The integrated of our new data with published sedimentological records suggests that the Huangling Massif might have been the watershed of the middle reaches of the Paleo-Yangtze River since the Cretaceous. At that time, the rivers flowed westward into the Sichuan Basin and eastward into the Jianghan Basin. The subduction of the Pacific Plate beneath the Asian continent in the Mesozoic deeply influenced the geomorphic evolution of the South China Block.
{"title":"Late Mesozoic Exhumation of the Huangling Massif: Constraints on the Evolution of the Middle Yangtze River","authors":"Jianchao SU, Xu LIN, Chang'an LI, Jolivet MARC, Lin WU, Feng CHENG, Bin DENG, Zhonghai WU, Xiaokang CHEN, Chengwei HU","doi":"10.1111/1755-6724.15117","DOIUrl":"10.1111/1755-6724.15117","url":null,"abstract":"<p>Plate subduction leads to complex exhumation processes on continents. The Huangling Massif lies at the northern margin of the South China Block. Whether the Huangling Massif was exhumed as a watershed of the middle reaches of the Paleo-Yangtze River during the Mesozoic remains under debate. We examined the exhumation history of the Huangling Massif based on six granite bedrock samples, using apatite fission track (AFT) and apatite and zircon (U-Th)/He (AHe and ZHe) thermochronology. These samples yielded ages of 157–132 Ma (ZHe), 119–106 Ma (AFT), and 114–72 Ma (AHe), respectively. Thermal modeling revealed that three phases of rapid cooling occurred during the Late Jurassic–Early Cretaceous, late Early Cretaceous, and Late Cretaceous. These exhumation processes led to the high topographic relief responsible for the emergence of the Huangling Massif. The integrated of our new data with published sedimentological records suggests that the Huangling Massif might have been the watershed of the middle reaches of the Paleo-Yangtze River since the Cretaceous. At that time, the rivers flowed westward into the Sichuan Basin and eastward into the Jianghan Basin. The subduction of the Pacific Plate beneath the Asian continent in the Mesozoic deeply influenced the geomorphic evolution of the South China Block.</p>","PeriodicalId":7095,"journal":{"name":"Acta Geologica Sinica ‐ English Edition","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2023-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135647842","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Hesar pluton in the northern Urumieh–Dokhtar magmatic arc hosts numerous mafic-microgranular enclaves (MMEs). Whole rock geochemistry, mineral chemistry, zircon U-Pb and Sr-Nd isotopes were measured. It is suggested that the rocks are metaluminous (A/CNK = 1.32–1.45), subduction-related I-type calc-alkaline gabbro to diorite with similar mineral assemblages and geochemical signatures. The host rocks yielded an U-Pb crystallization age of 37.3 ± 0.4 Ma for gabbro-diorite. MMEs have relatively low SiO2 contents (52.9–56.6 wt%) and high Mg# (49.8–58.7), probably reflecting a mantle-derived origin. Chondrite- and mantle-normalized trace element patterns are characterized by LREE and LILE enrichment, HREE and HFSE depletion with slight negative Eu anomalies (Eu/Eu* = 0.86–1.03). The host rocks yield (87Sr/86Sr)i ratios of 0.70492–0.70510, positive εNd(t) values of +1.55–+2.06 and TDM2 of 707–736 Ma, which is consistent with the associated mafic microgranular enclaves ((87Sr/86Sr)i = 0.705014, εNd(t) = +1.75, TDM2 = 729 Ma). All data suggest magma-mixing for enclave and host rock formation, showing a complete equilibration between mixed-mafic and felsic magmas, followed by rapid diffusion. The TDM1(Nd) and TDM2(Nd) model ages and U-Pb dating indicate that the host pluton was produced by partial melting of the lower continental crust and subsequent mixing with injected lithospheric mantle-derived magmas in a pre-collisional setting of Arabian–Eurasian plates. Clinopyroxene composition indicates a crystallization temperature of ∼1000°C and a depth of ∼9 km.
{"title":"Mineral Chemistry, Trace Elements, Isotopic Analysis and Zircon U-Pb Dating in the Hesar Pluton, Northern UDMA, Iran: Implications for Pre-Collisional Magma Mixing","authors":"Kazem KAZEMI, Soroush MODABBERI, Parisa GHARIBNEJAD, Yilin XIAO, Fatemeh SARJOUGHIAN, Ali KANANIAN","doi":"10.1111/1755-6724.15118","DOIUrl":"10.1111/1755-6724.15118","url":null,"abstract":"<p>The Hesar pluton in the northern Urumieh–Dokhtar magmatic arc hosts numerous mafic-microgranular enclaves (MMEs). Whole rock geochemistry, mineral chemistry, zircon U-Pb and Sr-Nd isotopes were measured. It is suggested that the rocks are metaluminous (A/CNK = 1.32–1.45), subduction-related I-type calc-alkaline gabbro to diorite with similar mineral assemblages and geochemical signatures. The host rocks yielded an U-Pb crystallization age of 37.3 ± 0.4 Ma for gabbro-diorite. MMEs have relatively low SiO<sub>2</sub> contents (52.9–56.6 wt%) and high Mg<sup>#</sup> (49.8–58.7), probably reflecting a mantle-derived origin. Chondrite- and mantle-normalized trace element patterns are characterized by LREE and LILE enrichment, HREE and HFSE depletion with slight negative Eu anomalies (Eu/Eu* = 0.86–1.03). The host rocks yield (<sup>87</sup>Sr/<sup>86</sup>Sr)<sub>i</sub> ratios of 0.70492–0.70510, positive <i>ε</i><sub>Nd</sub>(<i>t</i>) values of +1.55–+2.06 and <i>T</i><sub>DM2</sub> of 707–736 Ma, which is consistent with the associated mafic microgranular enclaves ((<sup>87</sup>Sr/<sup>86</sup>Sr)<sub>i</sub> = 0.705014, <i>ε</i><sub>Nd</sub>(<i>t</i>) = +1.75, <i>T</i><sub>DM2</sub> = 729 Ma). All data suggest magma-mixing for enclave and host rock formation, showing a complete equilibration between mixed-mafic and felsic magmas, followed by rapid diffusion. The <i>T</i><sub>DM1</sub>(Nd) and <i>T</i><sub>DM2</sub>(Nd) model ages and U-Pb dating indicate that the host pluton was produced by partial melting of the lower continental crust and subsequent mixing with injected lithospheric mantle-derived magmas in a pre-collisional setting of Arabian–Eurasian plates. Clinopyroxene composition indicates a crystallization temperature of ∼1000°C and a depth of ∼9 km.</p>","PeriodicalId":7095,"journal":{"name":"Acta Geologica Sinica ‐ English Edition","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2023-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135739069","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Nianzi granite unit, which includes the Nianzi, Xiaolianghou and Xiawopu granitic intrusions, is a significant component of the northern part of the North China Craton (NCC) and is situated in the Yanshan fold and thrust belt (YFTB). However, there is still debate regarding the tectonic evolutionary history of the YFTB during the late Permian to Triassic period, specifically regarding the timing of subduction and collision between the NCC and the Paleo-Asian Ocean. The Nianzi granite unit exhibits unique petrological, geochronological and geochemical signatures that shed light on the tectonic evolutionary history of the YFTB. This study presents detailed petrology, whole-rock geochemistry, together with Sr-Nd isotopic, zircon U-Pb dating and Lu-Hf isotopic data of the granites within the Nianzi granite unit. Our findings demonstrate that the granites primarily consist of subhedral K-feldspar, plagioclase, quartz, minor biotite and hornblende, with accessory titanite, apatite, magnetite and zircon. Zircon U-Pb dating indicates that the Xiaolianghou granite was emplaced at 247.5 ± 0.62 Ma. Additionally, the adakitic characteristics of the Nianzi, Xiawopu and Xiaolianghou granitic intrusions, such as high Sr and Ba contents and high ratios of Sr/Y and (La/Yb)N, combined with negative Sr-Nd and Lu-Hf isotopes (87Sr/86Sr)i = 0.705681–0.7057433, εNd(t) = –21.98 to –20.97, zircon εHf(t) = –20.26 to –9.92), as well as the I-type granite features of high SiO2, Na2O and K2O/Na2O ratios, enriched Rb, K, Sr and Ba, along with depleted Th, U, Nb, Ta, P and Ti, suggest that the Nianzi granitic unit was mainly derived from the partial melting of a thickened lower crust containing hydrous, calc-alkaline to high-K calc-alkaline, mafic to intermediate metamorphic rocks. In light of these parameters, we further integrate our data with previous studies and conclude that the Nianzi granitic unit was generated in a post-collisional extensional environment during the Early Triassic.
年子花岗岩单元包括年子、小梁后和小窝铺花岗岩侵入体,是华北克拉通(NCC)北部的重要组成部分,位于燕山褶皱推覆带(YFTB)中。然而,关于燕山褶皱推覆带在二叠纪晚期至三叠纪的构造演化历史,特别是华北克拉通与古亚洲洋之间的俯冲和碰撞时间,仍存在争议。年子花岗岩单元显示出独特的岩石学、地质年代学和地球化学特征,揭示了YFTB的构造演化历史。本研究介绍了年子花岗岩单元内花岗岩的详细岩石学、全岩地球化学、Sr-Nd同位素、锆石U-Pb年代测定和Lu-Hf同位素数据。我们的研究结果表明,花岗岩主要由亚斜长石、斜长石、石英、少量斜长石和角闪石组成,并伴有榍石、磷灰石、磁铁矿和锆石。锆石U-Pb年代测定表明,小凉沟花岗岩的成因年代为247.5 ± 0.62 Ma。此外,年子、小窝铺和小凉沟花岗岩侵入体具有高Sr和Ba含量、高Sr/Y和(La/Yb)N比值等黑云母特征,Sr-Nd和Lu-Hf同位素为负值(87Sr/86Sr)i = 0.705681-0.7057433, εNd(t) = -21.98 to -20.97, 锆石εHf(t) = -20.26 to -9.92),以及高SiO2、Na2O和K2O/Na2O比值,富集Rb、K、Sr和Ba,贫化Th、U、Nb、Ta、P和Ti的I型花岗岩特征,表明年子花岗岩单元主要来源于含水、钙碱性至高K钙碱性、黑云母至中变质岩的增厚下地壳的部分熔融。根据这些参数,我们将我们的数据与之前的研究进一步整合,得出结论:年轮花岗岩单元产生于早三叠世碰撞后的伸展环境中。
{"title":"Petrogenesis and Tectonic Implications of the Early Triassic Nianzi Adakitic Granite Unit in the Yanshan Fold and Thrust Belt: New Constraints from U-Pb Geochronology and Sr-Nd-Hf Isotopes","authors":"Huijun ZHANG, Chu WU, Fubing HE, Biren WANG, Yubin CUI, Zhenghua LIU, Shina YOU, Jing DONG","doi":"10.1111/1755-6724.15112","DOIUrl":"10.1111/1755-6724.15112","url":null,"abstract":"<p>The Nianzi granite unit, which includes the Nianzi, Xiaolianghou and Xiawopu granitic intrusions, is a significant component of the northern part of the North China Craton (NCC) and is situated in the Yanshan fold and thrust belt (YFTB). However, there is still debate regarding the tectonic evolutionary history of the YFTB during the late Permian to Triassic period, specifically regarding the timing of subduction and collision between the NCC and the Paleo-Asian Ocean. The Nianzi granite unit exhibits unique petrological, geochronological and geochemical signatures that shed light on the tectonic evolutionary history of the YFTB. This study presents detailed petrology, whole-rock geochemistry, together with Sr-Nd isotopic, zircon U-Pb dating and Lu-Hf isotopic data of the granites within the Nianzi granite unit. Our findings demonstrate that the granites primarily consist of subhedral K-feldspar, plagioclase, quartz, minor biotite and hornblende, with accessory titanite, apatite, magnetite and zircon. Zircon U-Pb dating indicates that the Xiaolianghou granite was emplaced at 247.5 ± 0.62 Ma. Additionally, the adakitic characteristics of the Nianzi, Xiawopu and Xiaolianghou granitic intrusions, such as high Sr and Ba contents and high ratios of Sr/Y and (La/Yb)<sub>N</sub>, combined with negative Sr-Nd and Lu-Hf isotopes (<sup>87</sup>Sr/<sup>86</sup>Sr)<sub>i</sub> = 0.705681–0.7057433, <i>ε</i><sub>Nd</sub>(<i>t</i>) = –21.98 to –20.97, zircon <i>ε</i><sub>Hf</sub>(<i>t</i>) = –20.26 to –9.92), as well as the I-type granite features of high SiO<sub>2</sub>, Na<sub>2</sub>O and K<sub>2</sub>O/Na<sub>2</sub>O ratios, enriched Rb, K, Sr and Ba, along with depleted Th, U, Nb, Ta, P and Ti, suggest that the Nianzi granitic unit was mainly derived from the partial melting of a thickened lower crust containing hydrous, calc-alkaline to high-K calc-alkaline, mafic to intermediate metamorphic rocks. In light of these parameters, we further integrate our data with previous studies and conclude that the Nianzi granitic unit was generated in a post-collisional extensional environment during the Early Triassic.</p>","PeriodicalId":7095,"journal":{"name":"Acta Geologica Sinica ‐ English Edition","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2023-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134911175","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}