西秦岭北缘花岗质岩浆作用及构造演化   总被引：13，自引：9，他引：4  

徐学义  陈隽璐  高婷  李平  李婷 《岩石学报》2014,30(2):371-389

西秦岭北部江里沟、阿夷山、德乌鲁、温泉和中川5个花岗质岩体岩石学、地球化学和LA-ICP-MS锆石U-Pb年代学研究结果表明,花岗岩体的岩性主体为花岗闪长岩-二长花岗岩,属高钾钙碱系列,少数为钙碱系列;形成时代为264~216Ma。江里沟、阿夷山和中川岩体属弱过铝质花岗岩(ACNK1.05),温泉岩体和德乌鲁岩体属准铝和弱过铝质花岗岩(ACNK=0.95~1.05);花岗岩具有埃达克岩(Sr400×10-6,Yb2×10-6)或喜马拉雅型花岗岩(Sr400×10-6,Yb2×10-6)的地球化学特征,或两者兼而有之。花岗岩浆起源于下地壳的部分熔融,源岩最有可能是古老的玄武质岩石。西秦岭北部存在埃达克岩和喜马拉雅型花岗岩,说明三叠纪时期存在陆陆碰撞或陆陆俯冲导致的地壳加厚,加厚的下地壳的部分熔融以及部分熔融发生深度的不同,形成本区具有埃达克或喜马拉雅型地球化学特点的花岗岩侵入体。埃达克岩和喜马拉雅型花岗岩对寻找金铜矿产具有一定的指导意义。  相似文献   

Zedong terrane revisited: An intra-oceanic arc within Neo-Tethys or a part of the Asian active continental margin?     

《Journal of Asian Earth Sciences》2014

Precise timing of the India-Asia collision is important to constrain the evolution history of both the Himalayan orogen and the Tibetan Plateau. It has been proposed that the Indian plate first collided with an intra-oceanic arc at ∼55 Ma, and then the composite terrane collided with the Asian continent at ∼35 Ma. The Zedong terrane has been suggested to represent the vestige of such an intra-oceanic arc developed within the Neo-Tethys Ocean, as some volcanic rocks with high K₂O have been classified as shoshonites. In this study, we present detailed geochemical and geochronological data of various types of magmatic rocks (including volcanic, cumulate and granitic rocks) widely exposed in the Zedong terrane to constrain the formation age and tectonic setting of the Zedong terrane. We found that the Zedong volcanic rocks belong to calc-alkaline series rather than shoshonites and high K₂O contents in some volcanic rocks resulted from alteration. The basalts are highly enriched in LREE and LILE, but strongly depleted in HFSE, indicating they were derived from a metasomatized mantle. Presence of hornblende phenocryst in both gabbros and hornblendites indicates that the cumulates were produced from hydrous basalts through crystallization. The granitic rocks have adakite-like compositional characteristics, i.e., high Sr/Y ratios but low Y contents, which were formed by melting of a thickened lower crust. Zircons from six samples, including a volcanic rock (an andesite), three cumulates (a hornblendites, a hornblende-bearing gabbro and a gabbro) and two granitic (a tonalite and a granodiorite) rocks, have been dated to yield identical ages of ∼155–160 Ma. This suggests that the volcanic eruption and plutonic emplacement were coevally developed in the Zedong terrane. Zircons from both the andesite and the cumulates have similar positive ε_Hf(t) values (∼+11.6 to +16.7), indicating they were stemmed from similarly depleted mantle sources. Meanwhile, zircons from the granitic rocks also have positive ε_Hf(t) values of ∼+12.6 to +15.2, implying their derivation from a juvenile lower crust. Therefore, we proposed that the basalts in the Zedong terrane were formed through partial melting of the mantle wedge metasomatized by slab-released fluids/melts. A part of hydrous basalts were underplated in the thickened lower crust beneath the Zedong terrane, which gave rise to the cumulate and granitic rocks. By comparison, magmatic rocks in the Zedong terrane show compositional similarities with the Jurassic rocks exposed in the Gangdese arc. This suggests that the Zedong terrane represents a slice of the active continental margin developed on the southern margin of the Lhasa terrane as a result of the northward subduction of the Neo-Tethys Ocean during the Late Jurassic, rather than the vestige of an intra-oceanic arc.  相似文献   

苏鲁超高压变质带东北端多种成因类型变基性岩:来自岩石学、同位素年代学及地球化学属性的制约   总被引：2，自引：2，他引：0  

刘利双  刘福来  王伟 《岩石学报》2017,33(9):2899-2924

苏鲁超高压变质带是扬子板块与华北板块在三叠纪俯冲-碰撞的产物。变基性岩是苏鲁超高压变质带内出露最广泛的岩石类型之一,研究其岩石学、年代学、地球化学属性及成因机制,对于揭示扬子板块与华北板块之间的俯冲-碰撞-折返的动力学过程具有重要的科学意义。以(退变)榴辉岩为代表的超高压变质岩石广泛出露在威海-荣成一带,少量出露在乳山地区。锆石LA-ICP-MS U-Pb定年结果显示,(退变)榴辉岩的原岩时代为792~760Ma,峰期榴辉岩相变质时代为243~226Ma,后期角闪岩相退变质时代为221~207Ma。非榴辉岩相变质的基性岩(麻粒岩和斜长角闪岩)主要出露在乳山地区,其原岩形成时代应不晚于古元古代(1939Ma),峰期麻粒岩相变质时代为1895~1870Ma,后期角闪岩相退变质时代为1848~1806Ma,与胶北地体变基性岩的原岩时代和变质时代十分相似。全岩地球化学研究结果表明,(退变)榴辉岩的原岩显示高Fe拉斑玄武岩的特点,根据其稀土和微量元素特征,可将(退变)榴辉岩进一步划分为A、B和C三组。在球粒陨石标准化稀土配分模式和原始地幔均一化蛛网图解上,A、B和C三组样品分别具有轻稀土弱亏损、轻稀土弱富集和轻稀土富集的特点。轻稀土富集或弱富集型(退变)榴辉岩的原岩地球化学性质与岛弧或大陆玄武岩相似,它们的源区可能与深部富集地幔或受流体交代的地幔楔存在密切的成因关系;而轻稀土亏损型(退变)榴辉岩的原岩可能来自于亏损地幔的部分熔融。由此可见,(退变)榴辉岩的原岩具有成因多样性的特点。乳山地区的基性麻粒岩和斜长角闪岩的原岩也具有高Fe拉斑玄武岩的地球化学属性,Al2O3与Mg O呈正相关变化,TiO_2、P_2O_5与MgO表现出一定程度的负相关性。绝大多数非榴辉岩相变质基性岩的球粒陨石标准化稀土配分模式和原始地幔均一化蛛网配分曲线具有微右倾或明显右倾的特点。上述特征表明,研究区绝大多数非榴辉岩相变质的基性岩原岩来自于富集地幔,少数来自于原始地幔或亏损地幔,并经历了斜长石和辉石的分离结晶以及不同程度的部分熔融过程。由此可见,乳山地区出露的非超高压变质基性岩的原岩具有与胶北地体(高压)基性麻粒岩相近的成因特点。岩石学、同位素年代学和地球化学特征的综合对比研究结果表明,在苏鲁超高压变质带东北端的威海-荣成-乳山地区,既存在与华北板块古老变质基底相关的变基性岩,也存在与华南板块北缘新元古代变质基底相关的超高压榴辉岩,表明三叠纪时期华北板块东南缘胶北地体的部分古老变质基底曾卷入到扬子板块与华北板块之间的俯冲-碰撞造山过程,随后与超高压岩石一起抬升折返,形成当今的构造混杂岩带。  相似文献   

大陆的起源     

赵国春  张国伟 《地质学报》2021,95(1):1-19

太阳系固体星球都有类似的核-幔-壳结构,但唯独人类居住的地球具有长英质组成的大陆壳.太古宙大陆克拉通主要由英云闪长岩(Tonalite)-奥长花岗岩(Trondhjemite)-花岗闪长岩(Granodiorite)为主的TTG深成侵入体变质而成的正片麻岩和由基性-超基性酸性火山岩及少量沉积岩变质的表壳岩(绿岩)组成....  相似文献   

扬子板块西北缘碧口微地块南华系碎屑锆石U-Pb年龄及其物源示踪          下载免费PDF全文

毛帆  裴先治  李瑞保  李佐臣  裴磊  刘成军  赵少伟  高峰  陈有炘  周海 《沉积与特提斯地质》2021,41(1):41-57

扬子板块西北缘碧口微地块红岩沟地区碧口群火山岩系之上发育有南华—震旦纪沉积盖层,但南华系的沉积时代尚缺乏依据,其物源及构造背景也仍无定论.本文采用LA-ICP-MS锆石U-Pb测年方法,对南华系上部含砾岩系中的长石砂岩进行了碎屑锆石测年研究,结果表明碎屑锆石的年龄可以分为两组:(1)新元古代晚期年龄组(750～800M...  相似文献   

Affinity between Palaeozoic Blocks of Xinjiang and Their Suturing Ages   总被引：1，自引：0，他引：1  

GUO Fuxiang Research Centre of Prediction of Hidden Ore Deposits  Guilin Institute of Technology  Guilin 《《地质学报》英文版》2000,74(1):1-6

The Kazakhstanian plate was near the Tarim, Sino-Korean and South China-Southeast Asian plates in the Middle-Late Cambrian and Late Ordovician, and approached the Siberian plate in the other periods of the Early Palaeozoic. The Hi and Toksun-Yamansu terranes had been split from the Tarim plate before the Middle Devonian and then went close to Angaraland in the late Early Permian. The Beishan area on the northeastern margin of the Tarim plate came close to Angaraland first in the early Early Permian. The suturing age between the Tarim and Ka-zakhstanian-Siberian plates is generally the same as that between the Turkey-Central Iran-Gangdise and South China-Southeast Asian plates. The suturing event took place in the early Early Permian, while the corresponding tectogeny occurred between the Early and Late Permian.  相似文献   

胶北地体侏罗纪花岗岩的成因及其构造意义     

周珊  孟凡雪  谢士稳 《岩石矿物学杂志》2021,40(5):874-896

胶北地体中生代花岗岩广泛分布,以晚侏罗世最为发育,花岗岩形成时代、成因和地球动力学背景的深入研究对认识研究区构造演化有重要意义.本文选取胶北地体东部和北部侏罗纪花岗岩进行全岩主微量元素、锆石U-Pb年龄和O同位素研究,结果表明,花岗岩样品锆石U-Pb年龄主要分布在166～156 Ma之间,代表岩体的结晶年龄.此外,含有...  相似文献