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Chronological and geochemical variations of the late Mesozoic granitoids in the Taihang Mountains and middle-southern Tan-Lu Fault: Implications for lithosphere destruction of the North China Craton 太行山和郯庐断裂中南部晚中生代花岗岩的年代和地球化学变化——对华北克拉通岩石圈破坏的启示
IF 2.9 3区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2021-06-01 DOI: 10.2475/06.2021.04
Yuelan Kang, Yuruo Shi, J. Anderson
In the Late Mesozoic, the North China Craton (NCC) underwent significant lithospheric thinning and destruction, especially in the eastern part, but the mechanism and timing related to this process are still contentious. The Taihang Mountains (TH) are located in the western part of the eastern NCC and the Tan-Lu Fault (TLF) is in the eastern part, which are two essential magmatic areas that reveal deep processes of magma origin. We investigated the spatial-temporal distribution of igneous rocks from these two areas to constrain the tectonic setting and magmatic sources. SHRIMP zircon U-Pb ages of the granitoids within the Fangshan pluton in northern TH area range from 136 to 128 Ma. Their εHf(t) values and δ18O values show ranges of −27.7 to −18.5 and 6.68 to 7.26 permil, respectively. Hence, we conclude that the rocks were formed by mixing between underplating magma and the melts from the lower crust. The O-Hf isotopic compositions of six granitoid samples from the Yunmengshan complex in northern TH are also reported. In combination with previous studies, we propose that the geochemical characteristics of the magmatic rocks from the TH area had insignificant changes during late Mesozoic time, but the rocks from the TLF area varied greatly. The difference between those two areas may reflect the diverse impact of the Paleo-Pacific subduction process. The high Mg# adakitic rocks (HMA) from TLF area have higher Mg# values than the HMA rocks from TH area. Our conclusion is that the HMA rocks in the TLF area were mainly formed by delaminated lower crust interacting with mantle materials and that the Paleo-Pacific subduction had limited impact on TH magmas. Based on chronology and geochemical characteristics, we recognize three stages: 1) ∼166 to 140 Ma, multi-directional compression resulted in crustal shortening and thickening in the NCC, accompanied by regional partial melting of the crust and underplating of mafic magmas, 2) 140 to 125 Ma, the TLF underwent left-lateral strike-slip movement. Subsequent delamination of the lower crust around the fault and the NCC evolved into an extensional tectonic environment, 3) after 125 Ma, a large-scale extension of the NCC occurred likely due to stress relaxation after delamination. The TLF acted as a favorable channel for transporting mantle material and fluids, which implies that the large-scale fault zone was a key factor of the NCC lithosphere destruction.
在中生代晚期,华北克拉通(NCC)经历了显著的岩石圈减薄和破坏,尤其是在东部,但与这一过程相关的机制和时间仍存在争议。太行山(TH)位于北卡罗莱纳州东部的西部,郯庐断裂(TLF)位于东部,是揭示深层岩浆成因过程的两个重要岩浆区。我们研究了这两个地区火成岩的时空分布,以限制构造背景和岩浆来源。TH区北部房山岩体中花岗质岩石的SHRIMP锆石U-Pb年龄范围为136~128Ma,εHf(t)值和δ18O值范围分别为−27.7~−18.5和6.68~7.26。因此,我们得出结论,这些岩石是由底侵岩浆和下地壳熔体混合形成的。本文还报道了云南北部云梦山杂岩体6个花岗岩样品的O—Hf同位素组成。结合前人的研究,我们认为TH地区岩浆岩的地球化学特征在中生代晚期变化不大,但TLF地区的岩石变化很大。这两个区域之间的差异可能反映了古太平洋俯冲过程的不同影响。TLF地区的高Mg#adakitic岩石(HMA)的Mg#值高于TH地区的HMA岩石。我们的结论是,TLF地区的HMA岩石主要是由分层的下地壳与地幔物质相互作用形成的,古太平洋俯冲对TH岩浆的影响有限。根据年表和地球化学特征,我们确定了三个阶段:1)~166-140 Ma,多向挤压导致NCC地壳缩短和增厚,伴随着地壳的区域部分熔融和镁铁质岩浆的底侵作用;2)140-125 Ma,TLF经历了左旋走滑运动。随后,断层和NCC周围的下地壳分层演化为伸展构造环境,3)125Ma后,NCC的大规模伸展可能是由于分层后的应力松弛。TLF是地幔物质和流体输送的有利通道,这表明大规模断裂带是NCC岩石圈破坏的关键因素。
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引用次数: 1
Preface 前言
IF 2.9 3区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2021-06-01 DOI: 10.2475/06.2021.10
Simon A. Wilde, Shoujie Liu, Y. Rojas‐Agramonte, Guochun Zhao
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引用次数: 0
Geodynamic Environment of the ca. 3800 Ma Outer Arc Group, Isua (Greenland) 约3800 Ma外弧群的地球动力学环境,伊苏阿(格陵兰)
IF 2.9 3区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2021-06-01 DOI: 10.2475/06.2021.01
A. Nutman, C. Friend, V. Bennett, M. V. Kranendonk, A. Chivas
The arcuate, 35 km long Isua supracrustal belt (ISB, southern West Greenland) contains the world's largest remnants of Eoarchean volcanic and sedimentary sequences. The ISB is broadly divided into: (i) the northern Inner Arc Group of 3720 to 3690 Ma rocks, and (ii) the southern Outer Arc Group of ca. 3800 Ma rocks which is bounded on its northern side by the highly tectonized ca. 3750 Ma Dividing Sedimentary Unit. The boundary between the two groups is a mylonite formed between 3685 and 3660 Ma. Despite the generally high strain, amphibolite facies metamorphism and layer-parallel dislocations that can thin or altogether excise some units, domains of lower deformation comprising ≪1% (qualitative assessment) of the Outer Arc Group contain relict sedimentary and igneous structures. Combined with zircon U-Pb geochronology and whole rock geochemistry, this enables the Outer Arc Group lithological sequence and geodynamic setting to be reconstructed. The lower part of the Outer Arc Group is dominated by metabasaltic amphibolites of the Mafic Volcanic formation in which rarely-preserved pillow structures indicate both their predominantly subaqueous eruption and also their stratigraphic facing. They erupted >3800 Ma, because they were first intruded by subconcordant sheets of fine-grained hypabyssal tonalite dated at 3803±3 Ma (Crowley, 2003) and then by coarser-grained 3795 to 3791 Ma tonalite-granodiorite, which forms a large deformed pluton along the south side of the ISB. This formation is succeeded by the Sedimentary formation whose base consists of discontinuous rare, thin fuchsitic quartzites with 3890 to 3805 Ma detrital zircons. Overlying is a diverse package of dolostones, marls and siliceous rocks. Although they are extensively modified by metamorphism and metasomatism, producing widespread growth of talc or tremolite, relict graded sedimentary layering, chemical and isotopic signatures indicate originally sedimentary protoliths. Detrital zircons in these rocks range in age from ca. 3820 to 3805 Ma. This unit shows an upwards transition from ‘pure' chemical sedimentary rocks with distinct seawater-like trace element signatures into lithologies increasingly contaminated by felsic material that is locally preserved as graded layers, which are interpreted as an increasing volcanogenic input. Succeeding the sedimentary rocks is the Felsic Volcanic formation, an extensive unit of mostly schistose 3807 to 3802 Ma felsic potassic-altered rocks with carbonate-rich interludes and veins. Locally-preserved andesitic units with graded layering, massive vesicular lavas, polymict breccias, resorbed quartz phenocrysts and fiammé, attest to volcanic and volcano-sedimentary protoliths. Whole rock geochemistry and oxygen isotope analyses on these rocks and their zircons indicate predominantly felsic volcanic protoliths that experienced massive alteration in a surficial environment, probably following subaerial eruption. Massive volcanic rocks are commonest in th
35公里长的弧形Isua表壳带(ISB,格陵兰岛西南部)包含了世界上最大的始新世火山和沉积序列遗迹。ISB大致分为:(i)3720至3690 Ma岩石的北部内弧群,和(ii)约3800 Ma岩石的南部外弧群,其北侧以高度构造化的约3750 Ma划分沉积单元为界。两组之间的边界是形成于3685至3660 Ma之间的糜棱岩。尽管存在普遍的高应变、角闪岩相变质作用和层平行位错,这些位错可以使一些单元变薄或完全切除,但外弧组1%(定性评估)的较低变形域包含残余沉积和火成岩结构。结合锆石U-Pb地质年代学和全岩地球化学,可以重建外弧群的岩性序列和地球动力学背景。外弧群的下部主要由镁铁质火山岩组的变玄武岩角闪岩组成,其中很少保存的枕状结构表明它们主要是水下喷发,也表明它们面向地层。它们喷发了3800 Ma以上,因为它们首先被3803±3 Ma的细粒浅成英云闪长岩次心线片侵入(Crowley,2003),然后被3795至3791 Ma的粗粒英云闪长岩-花岗闪长岩侵入,后者沿ISB南侧形成一个大的变形深成岩体。该地层之后是沉积地层,其基底由不连续的稀有薄紫红色石英岩组成,具有3890至3805 Ma的碎屑锆石。覆盖层由白云岩、泥灰岩和硅质岩组成。尽管它们受到变质作用和交代作用的广泛改造,产生了滑石或透闪石的广泛生长,但残留的分级沉积分层、化学和同位素特征表明原始沉积原岩。这些岩石中的碎屑锆石的年龄范围为约3820至3805 Ma。该单元显示出从具有明显的海水状微量元素特征的“纯”化学沉积岩向上过渡到越来越多地被长英质物质污染的岩性,长英质材料被局部保存为分级层,这被解释为火山成因输入的增加。沉积岩之后是长英质火山岩组,这是一个广泛的单元,主要由3807至3802 Ma的片状长英质钾质蚀变岩组成,具有富含碳酸盐的夹层和矿脉。局部保存的安山岩单元,具有分级分层、块状泡状熔岩、复相角砾岩、再吸收石英斑晶和fiammé,证明了火山和火山沉积原岩。对这些岩石及其锆石的全岩地球化学和氧同位素分析表明,长英质火山原岩主要在地表环境中经历了大规模蚀变,可能是在陆上喷发之后。块状火山岩在ISB西部最为常见,这表明该带的这一部分靠近火山中心。利用这些地层数据,我们得出结论,ISB火山岩和沉积岩是在类似板块构造的移动地球动力学机制中形成的,而不是在停滞的盖层机制中。
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引用次数: 2
Deciphering paleogeography from orogenic architecture: Constructing orogens in a future supercontinent as thought experiment 从造山带构造解读古地理:在未来的超大陆构造造山带作为思想实验
IF 2.9 3区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2021-06-01 DOI: 10.2475/06.2021.09
Douwe J. J. van Hinsbergen,Thomas L. A. Schouten
Orogens that form at convergent plate boundaries typically consist of accreted rock units that form an incomplete archive of subducted oceanic and continental lithosphere, as well as of deformed lithosphere of the former upper plate. Reading the construction of orogenic architecture forms the key to decipher the pre-orogenic paleogeographic distribution of oceans and continents, as well as bathymetric and topographic features that existed thereon such as igneous plateaus, seamounts, microcontinents, or magmatic arcs. Current classification schemes of orogens divide between settings associated with termination of subduction [continent-continent collision, continent-ocean collision (obduction)] and with ongoing subduction (accretionary orogenesis), alongside intraplate orogens. Perceived diagnostic features for such classifications, particularly of collisional orogenesis, hinge on dynamic interpretations linking downgoing plate paleogeography to upper plate deformation, plate motion changes, or magmatism. Here, we show, however, that Mesozoic-Cenozoic orogens that undergo collision almost all defy these proposed diagnostic features and behave as accretionary orogens instead. To reconstruct paleogeography of subducted and upper plates, we therefore propose an alternative approach to navigating through orogenic architecture: subducted plate units comprise nappes (or mélanges) with Ocean Plate Stratigraphy (OPS) and Continental Plate Stratigraphy (CPS) stripped from their now-subducted or otherwise underthrust lower crustal and mantle lithospheric underpinnings. Upper plate deformation and paleogeography respond to the competition between absolute motions of the upper plate and the subducting slab. Our navigation approach through orogenic architecture aims to avoid a priori dynamic interpretations that link downgoing plate paleogeography to deformation or magmatic responses in the upper plate, to provide an independent basis for geodynamic analysis. From our analysis we identify ‘rules of orogenesis' that link the rules of rigid plate tectonics with the reality of plate deformation. We use these rules for a thought experiment, in which we predict orogenic architecture that will result from subducting the present-day Indian Ocean and colliding the Somali, Madagascar, and Indian margins using a published continental drift scenario for a future supercontinent as basis. We illustrate that our inferred rules (of thumb) generate orogenic architecture that is analogous to elements of modern orogens, unlocking the well-known modern geography as inspiration for developing testable hypotheses that aid interpreting paleogeography from orogens that formed since the birth of plate tectonics.
在会聚板块边界形成的造山带通常由增生的岩石单元组成,这些单元形成了俯冲的海洋和大陆岩石圈以及前上板块变形的岩石圈的不完整档案。阅读造山构造是破译海洋和大陆的前造山古地理分布,以及存在于其上的火成岩高原、海山、微大陆或岩浆弧等水深和地形特征的关键。目前造山带的分类方案分为与俯冲结束[大陆-大陆碰撞,大陆-海洋碰撞(逆冲)]和与持续俯冲(增生造山)有关的背景,以及与板内造山带有关的背景。这种分类的可感知诊断特征,特别是碰撞造山作用,取决于将下行板块古地理与上板块变形、板块运动变化或岩浆作用联系起来的动力学解释。然而,在这里,我们表明,经历碰撞的中新生代造山带几乎都违背了这些提出的诊断特征,而表现为增生造山带。因此,为了重建俯冲和上板块的古地理,我们提出了一种通过造山带构造导航的替代方法:俯冲板块单元包括推覆体(或称m langes)和海洋板块地层学(OPS)和大陆板块地层学(CPS),它们从现在俯冲或逆冲的下地壳和地幔岩石圈基础中剥离出来。上板块的变形和古地理是对上板块与俯冲板块绝对运动竞争的反应。我们通过造山带构造的导航方法旨在避免将下行板块古地理与上板块的变形或岩浆反应联系起来的先验动力学解释,为地球动力学分析提供独立的基础。从我们的分析中,我们确定了“造山规则”,它将刚性板块构造的规则与板块变形的现实联系起来。我们用这些规则做了一个思想实验,在这个实验中,我们预测造山带的构造将会由今天印度洋的俯冲和索马里、马达加斯加和印度边缘的碰撞而产生,并使用已发表的未来超大陆的大陆漂移情景作为基础。我们说明,我们推断的规则(经验)产生的造山带结构类似于现代造山带的元素,为开发可测试的假设提供灵感,这些假设有助于解释自板块构造诞生以来形成的造山带的古地理。
{"title":"Deciphering paleogeography from orogenic architecture: Constructing orogens in a future supercontinent as thought experiment","authors":"Douwe J. J. van Hinsbergen,Thomas L. A. Schouten","doi":"10.2475/06.2021.09","DOIUrl":"https://doi.org/10.2475/06.2021.09","url":null,"abstract":"Orogens that form at convergent plate boundaries typically consist of accreted rock units that form an incomplete archive of subducted oceanic and continental lithosphere, as well as of deformed lithosphere of the former upper plate. Reading the construction of orogenic architecture forms the key to decipher the pre-orogenic paleogeographic distribution of oceans and continents, as well as bathymetric and topographic features that existed thereon such as igneous plateaus, seamounts, microcontinents, or magmatic arcs. Current classification schemes of orogens divide between settings associated with termination of subduction [continent-continent collision, continent-ocean collision (obduction)] and with ongoing subduction (accretionary orogenesis), alongside intraplate orogens. Perceived diagnostic features for such classifications, particularly of collisional orogenesis, hinge on dynamic interpretations linking downgoing plate paleogeography to upper plate deformation, plate motion changes, or magmatism. Here, we show, however, that Mesozoic-Cenozoic orogens that undergo collision almost all defy these proposed diagnostic features and behave as accretionary orogens instead. To reconstruct paleogeography of subducted and upper plates, we therefore propose an alternative approach to navigating through orogenic architecture: subducted plate units comprise nappes (or mélanges) with Ocean Plate Stratigraphy (OPS) and Continental Plate Stratigraphy (CPS) stripped from their now-subducted or otherwise underthrust lower crustal and mantle lithospheric underpinnings. Upper plate deformation and paleogeography respond to the competition between absolute motions of the upper plate and the subducting slab. Our navigation approach through orogenic architecture aims to avoid a priori dynamic interpretations that link downgoing plate paleogeography to deformation or magmatic responses in the upper plate, to provide an independent basis for geodynamic analysis. From our analysis we identify ‘rules of orogenesis' that link the rules of rigid plate tectonics with the reality of plate deformation. We use these rules for a thought experiment, in which we predict orogenic architecture that will result from subducting the present-day Indian Ocean and colliding the Somali, Madagascar, and Indian margins using a published continental drift scenario for a future supercontinent as basis. We illustrate that our inferred rules (of thumb) generate orogenic architecture that is analogous to elements of modern orogens, unlocking the well-known modern geography as inspiration for developing testable hypotheses that aid interpreting paleogeography from orogens that formed since the birth of plate tectonics.","PeriodicalId":7660,"journal":{"name":"American Journal of Science","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2021-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138504451","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}
引用次数: 0
An Early Paleoproterozoic back-arc system along the southern margin of the Yinshan Block: Evidence from a newly-defined bimodal volcanic sequence in the Daqingshan Complex, Khondalite Belt 阴山地块南缘早古元古代弧后系统——来自孔达岩带大青山杂岩新定义的双峰火山序列的证据
IF 2.9 3区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2021-06-01 DOI: 10.2475/06.2021.03
X. Wang, Jian Zhang, C. Yin, Hai Zhou, Jin Liu, Wenxia Zhang, Shuhui Zhang, Chen Zhao, Changquan Cheng
As one of the 2.1 to 1.9 Ga orogenic belts that welded the Columbia supercontinent, the Khondalite Belt in the North China Craton is a typical continent-continent collisional orogen that formed through the collision between the Yinshan and Ordos Blocks. Previous studies mostly focused on the collisional event in the Khondalite Belt but paid little attention to how the subduction system operated before the final closure of the ocean. To address this issue, we identified a series of interlayered meta-mafic and felsic rock assemblages in the Daqingshan Complex and implemented geochemical and geochronological analyses. Petrological and geochemical studies revealed that these rocks are bimodal and include plagioclase amphibolite (Group 1) and biotite plagiogneiss (Group 2). Geochemically, Group 1 samples show tholeiitic affinity, whereas Group 2 samples belong to the high-K calc-alkaline series. Geochemical data indicate that the protolith magma of Group 1 was most likely derived from the partial melting of lithospheric mantle with minor crustal contamination, whereas Group 2 rocks represent highly differentiated magma derived from the partial melting of ancient crustal materials. All the samples show depletion of HFSEs and enrichment of LILEs, indicative of a subduction-related magmatic arc environment. Zircon U-Pb dating results show that the protoliths of Group 1 samples yield crystallization ages of ∼2.47 Ga and metamorphic ages of 1.95 to 1.85 Ga, whereas the protoliths of Group 2 samples yield crystallization ages of ∼2.40 Ga and metamorphic ages of ∼1.85 Ga. Our new results and available geochemical, petrological, and isotopic data demonstrate that the bimodal volcanic sequence of the Daqingshan Complex was developed in a 2.47 to 2.40 Ga back-arc system along the southern margin of Yinshan Block. Subsequent collision between the Ordos and Yinshan Blocks resulted in the formation of the Khondalite Belt and final amalgamation of the Western Block between 1.95 and 1.85 Ga.
华北克拉通孔达岩带是连接哥伦比亚超大陆的2.1~1.9Ga造山带之一,是由阴山地块与鄂尔多斯地块碰撞形成的典型大陆-大陆碰撞造山带。以前的研究大多集中在孔达利特带的碰撞事件上,但很少关注俯冲系统在海洋最终关闭前的运作。为了解决这个问题,我们在大青山杂岩中确定了一系列层间变镁铁质和长英质岩石组合,并进行了地球化学和地质年代分析。岩石学和地球化学研究表明,这些岩石是双峰岩石,包括斜长石角闪岩(第1组)和黑云母斜长岩(第2组)。从地球化学角度来看,第1组样品显示出拉斑玄武岩的亲和力,而第2组样品属于高钾钙碱性系列。地球化学数据表明,第1组的原岩岩浆很可能来源于岩石圈地幔的部分熔融,地壳污染较小,而第2组岩石代表了来自古代地壳物质部分熔融的高分化岩浆。所有样品均显示HFSE的贫化和LILE的富集,表明存在俯冲相关的岩浆弧环境。锆石U-Pb定年结果表明,第1组样品的原岩产生约2.47 Ga的结晶年龄和1.95至1.85 Ga的变质年龄,而第2组样品的原石产生约2.40 Ga的晶化年龄和约1.85 Ga,同位素资料表明,大青山杂岩双峰火山序列发育于阴山地块南缘2.47~2.40 Ga的弧后系统中。鄂尔多斯地块和阴山地块之间随后的碰撞导致了孔达利特带的形成,以及1.95至1.85 Ga之间西部地块的最终合并。
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引用次数: 3
Composition and provenance analysis of beach sands in an almost isolated sedimentary system – A field study of the Galápagos Archipelago 一个几乎孤立的沉积体系中海滩砂的组成和物源分析- Galápagos群岛的实地研究
IF 2.9 3区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2021-06-01 DOI: 10.2475/05.2021.04
K. Seelos, Y. Rojas‐Agramonte, A. Kröner, T. Toulkeridis, Gillian Inderwies, Yvonne Buelow
The Galápagos Archipelago is the surface expression of an active hotspot or long-lived mantle plume. The Archipelago consists of a group of 13 main islands which are located in the eastern central Pacific Ocean about 1,000 km west of the northern edge of the South American continent, east of the East Pacific Rise and south of the Galápagos spreading center. Because of the large distance to the nearest continental land mass, Galapagos can be seen as an almost isolated sedimentary system. A provenance study conducted on samples collected from seventeen beaches on eleven islands, demonstrates that mineral grains and particles were derived from weathering of predominantly basaltic rocks and were transported within the islands, between the islands or inside the coastal area around the Archipelago. The exclusion of external sources allows advanced studies about erosion processes, transport pathways of particles and the accumulation of autochthonous sediments. The combined usage of optical particle size and shape analysis with RAMAN spectroscopy allows a successful spatial delimitation of host rocks and a reconstruction of transport pathways. The analyzed samples can be subdivided into three groups: 1) Type-A sediments: fine-grained and sampled on beaches of the oldest islands in the eastern part of Galápagos. The composition of volcanic minerals corresponds to the alkaline character of the basaltic source rocks. 2) Type-B: well sorted sediments characterized by medium-grained olivine, pyroxene, plagioclase and even a small amount of quartz grains. The islands of this group are located in the central region of the Archipelago. 3) Type-C samples: olivine and pyroxene are the predominant volcanic minerals. These samples indicate bimodal, coarse-grained size distributions and large proportions of pumice and are found in Floreana in the south and the youngest islands Isabela and Fernandina in the west of Galápagos.
Galápagos群岛是活跃热点或长寿命地幔柱的地表表现。该群岛由13个主要岛屿组成,位于太平洋中部东部,南美洲大陆北部边缘以西约1000公里,东太平洋隆起以东,Galápagos蔓延中心以南。由于离最近的大陆块距离很远,加拉帕戈斯群岛可以看作是一个几乎孤立的沉积体系。对从11个岛屿的17个海滩收集的样品进行的物源研究表明,矿物颗粒和颗粒主要来自玄武岩的风化作用,并在岛屿内、岛屿之间或群岛周围的沿海地区内运输。排除外部来源可以进一步研究侵蚀过程、颗粒的运输途径和本地沉积物的积累。结合使用光学颗粒大小和形状分析与拉曼光谱允许宿主岩石的成功空间划分和运输路径的重建。分析的样品可分为三组:1)a型沉积物:颗粒细,取样于Galápagos东部最古老岛屿的海滩上。火山矿物组成与玄武质烃源岩的碱性特征相对应。2) b型:分选良好,以中粒橄榄石、辉石、斜长石为特征,甚至含有少量石英颗粒。3) c型样品:橄榄石和辉石是主要的火山矿物。这些样品显示了双峰、粗粒度的尺寸分布和大量的浮石,并在南部的弗洛里亚纳岛和Galápagos西部最年轻的伊莎贝拉岛和费尔南迪纳岛发现。
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引用次数: 1
Reconstructing lost plates of the panthalassa ocean through Paleomagnetic data from circum-pacific accretionary orogens 利用环太平洋增生造山带的古地磁数据重建潘塔拉萨洋的失落板块
IF 2.9 3区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2021-06-01 DOI: 10.2475/06.2021.08
L. Boschman, D. Hinsbergen, C. Langereis, K. Flores, P. Kamp, D. Kimbrough, H. Ueda, S. H. Lagemaat, Erik van der Wiel, W. Spakman
The Panthalassa Ocean, which surrounded the late Paleozoic-early Mesozoic Pangea supercontinent, was underlain by multiple tectonic plates that have since been lost to subduction. In this study, we develop an approach to reconstruct plate motions of this subducted lithosphere utilizing paleomagnetic data from accreted Ocean Plate Stratigraphy (OPS). We first establish the boundaries of the Panthalassa domain by using available Indo-Atlantic plate reconstructions and restorations of complex plate boundary deformation at circum-Panthalassa trenches. We reconstruct the Pacific Plate and its conjugates, the Farallon, Phoenix, and Izanagi plates, back to 190 Ma using marine magnetic anomaly records of the modern Pacific. Then, we present new and review published paleomagnetic data from OPS exposed in the accretionary complexes of Cedros Island (Mexico), the Santa Elena Peninsula (Costa Rica), the North Island of New Zealand, and Japan. These data provide paleolatitudinal plate motion components of the Farallon, Phoenix and Izanagi plates, and constrain the trajectories of these plates from their spreading ridges towards the trenches in which they subducted. For 83 to 150 Ma, we use two independent mantle frames to connect the Panthalassa plate system to the Indo-Atlantic plate system and test the feasibility of this approach with the paleomagnetic data. For times prior to 150 Ma, and as far back as Permian time, we reconstruct relative and absolute Panthalassa plate motions such that divergence is maintained between the Izanagi, Farallon and Phoenix plates, convergence is maintained with Pangean continental margins in Japan, Mexico and New Zealand, and paleomagnetic constraints are met. The reconstruction approach developed here enables data-based reconstruction of oceanic plates and plate boundaries in the absence of marine magnetic anomaly data or mantle reference frames, using Ocean Plate Stratigraphy, paleo-magnetism, and constraints on the nature of circum-oceanic plate boundaries. Such an approach is a crucial next step towards quantitative reconstruction of the currently largely unknown tectonic evolution of the Earth's oceanic domains in deep geological time.
潘塔拉萨洋环绕着晚古生代-早中生代的盘古超大陆,其下方是多个构造板块,这些板块后来因俯冲而消失。在这项研究中,我们开发了一种利用增生海洋板块地层学(OPS)的古地磁数据重建俯冲岩石圈板块运动的方法。我们首先通过使用现有的印度-大西洋板块重建和潘塔拉萨海沟复杂板块边界变形的恢复,建立潘塔拉萨域的边界。我们利用现代太平洋的海洋磁异常记录重建了190 Ma前的太平洋板块及其共轭物Farallon、Phoenix和Izanagi板块。然后,我们介绍了在塞德罗斯岛(墨西哥)、圣埃琳娜半岛(哥斯达黎加)、新西兰北岛和日本的增生杂岩中暴露的OPS的新的和已发表的古地磁数据。这些数据提供了Farallon、Phoenix和Izanagi板块的古纬度板块运动分量,并限制了这些板块从扩张山脊到俯冲海沟的轨迹。对于83至150 Ma,我们使用两个独立的地幔框架将潘塔拉萨板块系统连接到印度-大西洋板块系统,并用古地磁数据测试了这种方法的可行性。对于150 Ma之前的时间,以及早在二叠纪的时间,我们重建了潘塔拉萨板块的相对和绝对运动,使得伊扎纳吉板块、法拉隆板块和菲尼克斯板块之间保持分歧,与日本、墨西哥和新西兰的盘古大陆边缘保持会聚,并满足古地磁约束。这里开发的重建方法能够在没有海洋磁异常数据或地幔参考系的情况下,利用海洋板块地层学、古地磁和环洋板块边界性质的约束,对海洋板块和板块边界进行基于数据的重建。这种方法是定量重建地球海洋在深部地质时代的构造演化的关键下一步。
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引用次数: 7
Petrogenesis and tectonic implications of TTG granitoids from the Daqingshan Complex of the Khondalite Belt, North China Craton 华北克拉通孔雀岩带大青山杂岩TTG花岗岩体成因及构造意义
IF 2.9 3区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2021-06-01 DOI: 10.2475/06.2021.02
X. Wang, Jian Zhang, C. Yin, Hai Zhou, Jin Liu, Xiaoguang Liu, Chen Zhao
Located in the Western Block of the North China Craton, the Khondalite Belt is one of the three Paleoproterozoic tectonic belts that were linked to the final assembly of the craton. At present, a popular model is that the Khondalite Belt was formed by the collision between the Yinshan and Ordos blocks at ∼1.95 Ga. However, the initiation of oceanic subduction and its related arc magmatism and accretionary process before the collisional event were poorly constrained. The Daqingshan Complex is located in the middle East part of the Khondalite Belt, and contains highly deformed and metamorphosed rock assemblages, and thus represents a key area to decipher the above issue. In this study, we carried out petrological, geochemical and geochronological analysis on the TTG granitoids of the Daqingshan Complex. Zircon U-Pb results from three typical TTG samples yielded upper intercept ages of 2545 ± 50 Ma, 2484 ± 68 Ma and 2452 ± 32 Ma, indicating that the TTG granitoids were emplaced in the late Neoarchean. Metamorphic zircons from two samples gave 207Pb/206Pb weighted mean ages of 1892 ± 53 Ma and 1906 ± 27 Ma, respectively, recording the timing of a continent-to-continent collisional event. Thirteen TTG granitoid samples are geochemically low-, medium- and high-K calc-alkaline, with metaluminous to peraluminous trends and are enriched in large-ion lithophile elements (LILEs) such as Rb, Ba, La, Ce, Nd, and depleted in high field strength elements (HFSEs) such as Nb and Ta. Chondrite-normalized rare earth element (REE) patterns show fractionation with (La/Yb) N ratios ranging from 8.20 to 27.47, with weak Eu negative anomalies (δEu = 0.50 – 0.98). In addition, TTG granitoids of the Daqingshan Complex belong to I-type granitoids, and their igneous protoliths were intimately related to a subduction-related magmatic arc environment. New results of this study reveal that the initial oceanic lithosphere subduction operated since ∼2.55 Ga along the southern margin of the Yinshan Block, and generated the coeval arc-related TTG granitoids. Closure of the ocean led to the final collision between the Yinshan and Ordos blocks and the amalgamation of the Western Block at 1.95 to 1.85 Ga.
孔雀岩带位于华北克拉通西地块,是与华北克拉通最终拼合相联系的三个古元古代构造带之一。目前流行的一种模式是,孔达利岩带是在~ 1.95 Ga由阴山地块与鄂尔多斯地块碰撞形成的。然而,对碰撞前洋俯冲的起始及其相关的弧岩浆活动和增生过程却知之甚少。大青山杂岩位于孔达利岩带的中东部,具有高度变形变质的岩石组合,是破解上述问题的关键区域。本文对大青山杂岩TTG花岗岩进行了岩石学、地球化学和年代学分析。3个典型TTG样品的锆石U-Pb上截距年龄分别为2545±50 Ma、2484±68 Ma和2452±32 Ma,表明TTG花岗岩类的侵位时间为新太古代晚期。两个变质锆石样品的207Pb/206Pb加权平均年龄分别为1892±53 Ma和1906±27 Ma,记录了大陆与大陆碰撞事件的时间。13个TTG花岗岩样地球化学特征为低、中、高钾钙碱性,具有偏铝质至过铝质倾向,富集Rb、Ba、La、Ce、Nd等大离子亲石元素,贫Nb、Ta等高场强元素。球粒陨石归一化稀土元素(REE)模式显示分异,(La/Yb) N比值在8.20 ~ 27.47之间,弱Eu负异常(δEu = 0.50 ~ 0.98)。此外,大青山杂岩体的TTG花岗岩体属于i型花岗岩体,其火成岩原岩与俯冲相关的岩浆弧环境密切相关。新的研究结果表明,自~ 2.55 Ga以来,阴山地块南缘发生了初始洋岩石圈俯冲,形成了与弧相关的同世TTG花岗岩类。在1.95 ~ 1.85 Ga,海洋的封闭导致了阴山地块与鄂尔多斯地块的最终碰撞和西部地块的合并。
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引用次数: 4
SOLUBILITY PRODUCT CONSTANTS FOR NATURAL DOLOMITE (0-200°C) THROUGH A GROUNDWATER-BASED APPROACH USING THE USGS PRODUCED WATER DATABASE – PART A 利用美国地质勘探局采出水数据库通过地下水方法测定天然白云石(0-200°c)的溶解度乘积常数-第a部分
IF 2.9 3区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2021-05-02 DOI: 10.31223/x5ps42
H. Robertson, Fiona Whitaker, Cathy Hollis, H. Corlett
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引用次数: 0
Paleoaltimetry of the Western Andes in Northern Chile (∼18.5–19.5°S) 智利北部西安第斯山脉的古高程测量(~ 18.5-19.5°S)
IF 2.9 3区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2021-05-01 DOI: 10.2475/05.2021.01
Sebastian Jimenez-Rodriguez, M. Dettinger, J. Quade, Kendra E. Murray
Establishing the timing of surface uplift in the Central Andes is essential for evaluating the geodynamic mechanisms responsible for mountain building and their role in the development of dry conditions along the western coasts of Peru and Chile. Here, we present new stable hydrogen isotopic values from stream waters and hydration water in volcanic glass from northern Chile (18.5–19.5°S) that show that the Western Cordillera was already elevated by the early Miocene. The hydrogen isotopic values of reconstructed surface waters obtained from ancient and modern volcanic glass indicate that the Western Cordillera in northern Chile attained modern elevations by at least 22.8 Ma. When combined with paleoaltimetric records from the Altiplano and northwestern Puna, these results demonstrate that surface uplift of the Andean plateau was a time-transgressive process that varied not just from west to east but also from north and south along the strike of the orogen. Our paleoaltimetry reconstruction also suggests that the Western Cordillera has blocked moisture coming from the east since at least the early Miocene, consistent with previously published evidence of arid-semiarid conditions in the Atacama Desert. However, hyperaridity on the western Andean slope developed later and appears to correspond with the timing of uplift in the Eastern Cordillera and Altiplano. Our results suggest that the growth of the Central Andean rain shadow relied not only on the elevation of the Western Cordillera but also on the widening of the plateau.
确定安第斯山脉中部地表隆起的时间对于评估造成造山的地球动力机制及其在秘鲁和智利西海岸干燥条件发展中的作用至关重要。在此,我们从智利北部(18.5-19.5°S)火山玻璃的溪流水和水化水中获得了新的稳定氢同位素值,表明西科迪勒拉在中新世早期已经升高。古、现代火山玻璃重建的地表水氢同位素值表明,智利北部西科迪勒拉至少在22.8 Ma之前达到现代海拔高度。当与Altiplano和Puna西北部的古高程记录相结合时,这些结果表明安第斯高原的表面隆起是一个时间海侵过程,不仅从西到东,而且沿着造山带的走向从北向南变化。我们的古测高重建还表明,至少从中新世早期开始,西科迪勒拉就阻挡了来自东部的水分,这与之前发表的阿塔卡马沙漠干旱-半干旱条件的证据一致。然而,安第斯山脉西坡的极度干旱发展较晚,似乎与东部科迪勒拉和高原的隆升时间一致。我们的研究结果表明,安第斯中部雨影的生长不仅依赖于西部科迪勒拉的海拔高度,而且还依赖于高原的拓宽。
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引用次数: 3
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