Ordovician Granitoids and Silurian Mafic Dikes in the Western Kunlun Orogen, Northwest China: Implications for Evolution of the Proto-Tethys     

ZHANG Qichao  WU Zhenhan  LI Shan  LI Kan  LIU Zhiwei  ZHOU Qing 《《地质学报》英文版》2019,93(1):30-49

The western Kunlun orogen in the northwest Tibet Plateau is related to subduction and collision of Proto-and Paleo-Tethys from early Paleozoic to early Mesozoic. This paper presents new LA-ICPMS zircon U-Pb ages and Lu-Hf isotopes, whole-rock major and trace elements, and Sr–Nd isotopes of two Ordovician granitoid plutons(466–455 Ma) and their Silurian mafic dikes(～436 Ma) in the western Kunlun orogen. These granitoids show peraluminous high-K calcalkaline characteristics, with(⁸⁷Sr/⁸⁶Sr)_i value of 0.7129–0.7224, ε_Nd(t) values of -9.3 to -7.0 and zircon ε_Hf(t) values of -17.3 to -0.2, indicating that they were formed by partial melting of ancient lower-crust(metaigneous rocks mixed with metasedimentary rocks) with some mantle materials in response to subduction of the Proto-Tethyan Ocean and following collision. The Silurian mafic dikes were considered to have been derived from a low degree of partial melting of primary mafic magma. These mafic dikes show initial ⁸⁷Sr/⁸⁶Sr ratios of 0.7101–0.7152 and ε_Nd(t) values of -3.8 to -3.4 and zircon ε_Hf(t) values of -8.8 to -4.9, indicating that they were derived from enriched mantle in response to post-collisional slab break-off. Combined with regional geology, our new data provide valuable insight into late evolution of the Proto-Tethys.  相似文献   

西南天山柯坪地区萨尔干基性岩脉U-Pb年代学及地球化学特征     

霍海龙  陈正乐  陈贵民  张青  韩凤彬  张文高 《地质力学学报》2019,25(S1):60-65

柯坪地区发育一套沿走滑断层侵位的萨尔干基性岩脉,其产出于西南天山造山带与塔里木克拉通的接触部位,具有重要的意义。文章通过对萨尔干基性岩脉样品进行锆石LA-ICP-MS U-Pb年代学、岩石地球化学分析,探讨西南天山中新生代陆内造山作用过程。结果表明,萨尔干基性岩脉的LA-ICP-MS锆石U-Pb年龄为（49.14±0.8） Ma,表明该套岩石形成于始新世。地球化学表明该套岩石形成于与青藏高原碰撞远程效应相关的构造背景。  相似文献   

New constraints on granulite facies metamorphism and melt production in the Lewisian Complex,northwest Scotland          下载免费PDF全文

Yves Feisel  Richard W. White  Richard M. Palin  Tim E. Johnson 《Journal of Metamorphic Geology》2018,36(6):799-819

In this study, we investigate the metamorphic history of the Assynt and Gruinard blocks of the Archean Lewisian Complex, northwest Scotland, which are considered by some to represent discrete crustal terranes. For samples of mafic and intermediate rocks, phase diagrams were constructed in the Na₂O–CaO–K₂O–FeO–MgO–Al₂O₃–SiO₂–H₂O–TiO₂–O₂ (NCKFMASHTO) system using whole‐rock compositions. Our results indicate that all samples equilibrated at similar peak metamorphic conditions of ~8–10 kbar and ~900–1,000°C, consistent with field evidence for in situ partial melting and the classic interpretation of the central region of the Lewisian Complex as representing a single crustal block. Melt‐reintegration modelling was employed in order to estimate probable protolith compositions. Phase equilibria calculated for these modelled undepleted precursors match well with those determined for a subsolidus amphibolite from Gairloch in the southern region of the Lewisian Complex. Both subsolidus lithologies exhibit similar phase relations and potential melt fertility, with both expected to produce orthopyroxene‐bearing hornblende granulites, with or without garnet, at the conditions inferred for the Badcallian metamorphic peak. For fully hydrated protoliths, prograde melting is predicted to first occur at ~620°C and ~9.5 kbar, with up to 45% partial melt predicted to form at peak conditions in a closed‐system environment. Partial melts calculated for both compositions between 610 and 1,050°C are mostly trondhjemitic. Although the melt‐reintegrated granulite is predicted to produce more potassic (granitic) melts at ~700–900°C, the modelled melts are consistent with the measured compositions of felsic sheets from the central region Lewisian Complex.  相似文献   

大别山北部蛇绿岩的地球化学制约   总被引：8，自引：1，他引：7  

刘贻灿  徐树桐 《矿物岩石》1999,19(1):68-73

常量元素,微量元素,稀土元素,Ｎｄ同位素及氧同位素地球化学特征表明,太别山北部变质镁铁－超镁铁质岩带中存在变质的蛇绿岩,它主要由变质橄榄岩,辉长岩（－辉绿岩？）和基性熔岩三部分组成,其中,变质的基性熔岩的亏损地幔模式年龄ｔＤＭ／Ｍａ＝１０３６．８～１２９３．８,εＮｄ（ｔ）＝７．２～７．７,表明它可能代表１０００Ｍａ左右形成于中等扩张速率（２ｃｍ／ａｄ左右）洋盆条件下的洋壳残片。  相似文献   

大别山辉石岩—辉长岩体的锆石U—Pb年龄及其地质意义   总被引：43，自引：6，他引：37  

李曙光  洪吉安  李惠民  江来利 《高校地质学报》1999,5(3):351-355

大别山北部祝家铺,小河口和椒岩三个辉石岩－辉长岩侵入体的锆石给出四个Ｕ－Ｐｂ谐和年龄,范围均在１２３￣１３０Ｍａ之间,这表明这些基性／超基性侵入体是碰撞后成因的。由于白垩纪花岗岩脉普遍穿切这些辉长岩体,说明大别山垩纪大规模岩浆事件,是从深部地幔部分熔融开始的,其热动力可能源于地幔上涌。  相似文献   

Tectonothermal history of the basement rocks in the western zone of the North China Craton and its tectonic implications   总被引：47，自引：0，他引：47  

Guochun Zhao  Simon A. Wilde  Peter A. Cawood  Liangzhao Lu 《Tectonophysics》1999,310(1-4):37-53

The basement of the North China Craton can be divided into the eastern, central and western zones, based on lithological, structural, metamorphic and geochronological data. The western zone comprises two different petrotectonic units: Archaean tonalitic–trondhjemitic–granodioritic (TTG) grey gneisses and metamorphic mafic rocks, and Palaeoproterozoic khondalite series. The former is characterized by isobaric cooling (IBC)-type anticlockwise P–T paths in the north-northwestern part of the zone and near-isothermal decompression (ITD)-type clockwise P–T paths in the eastern part, adjacent to the central zone. On the other hand, the tectonothermal evolution of Palaeoproterozoic khondalite series rocks is characterized exclusively by nearly isothermal decompression following the peak of metamorphism and then cooling, defining clockwise P–T paths. The Archaean TTG gneisses and associated mafic rocks with anticlockwise metamorphic P–T paths reflects an origin related to underplating and intrusion of mantle-derived magmas which may be derived from mantle plumes. They represent a late Archaean continental block in the western part of the North China Craton. The Palaeoproterozoic khondalite series rocks represent passive continental margin deposits. They were metamorphosed and deformed in the late Palaeoproterozoic during the amalgamation of the western continental block with another continental block in the east part of the North China Craton. The ITD-type clockwise P–T–t paths of the Palaeoproterozoic khondalite series rocks record the tectonothermal histories of the collision of the western and eastern continental blocks which resulted in the final assembly of the North China Craton at c. 1800 Ma.  相似文献   

塔里木地块西北缘震旦系发现二叠纪基性岩床侵入事件   总被引：2，自引：0，他引：2  

吴鸿翔  黄伟康  励音骐  林秀斌  陈汉林  程晓敢  章凤奇 《地质学报》2020,94(6):1869-1882

准确识别侵入岩和火山岩并厘定其形成时代是野外地质调查的一项基础工作,它们对认识区域岩浆事件序列和建立沉积地层年代格架具有重要的作用。塔里木地块西北缘阿克苏地区以出露连续的新元古界和丰富多样的新元古代岩浆岩而成为备受前寒武纪地质研究工作者关注的地区。本文通过遥感影像的识别、野外剖面地质调查和岩石学研究,发现塔里木西北缘阿克苏市西南部的震旦系中发育的基性岩具有典型的岩浆侵入特征,包括局部截切地层、包裹围岩块和内部结晶粗、边缘结晶细等特点。结合锆石U-Pb年代学研究,发现该地区震旦系发育的基性岩浆岩并不全是震旦纪玄武岩,有相当一部分是早二叠世(ca. 290Ma)侵入的辉绿岩岩床,其侵位年龄与塔里木二叠纪大规模溢流玄武岩的喷发时代接近,很可能是塔里木大火成岩省的重要组成部分。这期显著的岩浆热事件可能对该地区前寒武纪岩石重磁化产生重要影响,同时也启示今后开展塔里木北缘震旦纪岩浆作用研究时需要特别引起重视并加以仔细鉴别。  相似文献   

南阿尔金巴什瓦克基性麻粒岩的变质演化 P- T- t 轨迹     

郭晶  李云帅  张建新 《地质学报》2020,94(9):2698-2711

大陆碰撞造山带中高压麻粒岩的 P- T- t 轨迹研究对于理解造山带的热演化历史及大陆地壳的形成与演化具有重要的意义,然而,如何连接同位素年龄与变质演化过程是恢复和建立 P- T- t 轨迹的重点和难点。本文通过对南阿尔金巴什瓦克地区基性麻粒岩的详细岩相学研究,认为该基性麻粒岩经历了原岩阶段（M1）、峰期变质阶段（M2）、峰后退变质阶段（M3）以及晚期角闪岩相- 绿片岩相退变质阶段（M4）。其中,传统矿物温压计和矿物微量元素温压计获得该基性麻粒岩所记录的峰期变质条件分别为17. 5~22. 6 kbar,901~985℃ 和17~28 kbar,1012~1049℃,退变质阶段的温压条件为7. 6~10. 7 kbar,750~810℃。此外,锆石U- Pb 年代学结果表明基性麻粒岩的变质时代为491±3. 5 Ma (MSWD=0. 62),结合锆石和石榴子石的微量元素分配系数以及前人的实验岩石学数据,认为该变质时代记录了早古生代高压- 超高温的变质事件,进而恢复了南阿尔金基性麻粒岩所记录的顺时针 P- T- t 轨迹。  相似文献   

The Montecristo monzogranite (Northern Tyrrhenian Sea,Italy): a collisional pluton in an extensional setting     

FABRIZIO INNOCENTI  DAVID S. WESTERMAN  SERGIO ROCCHI  SONIA TONARINI 《Geological Journal》1997,32(2):131-151

The Montecristo monzogranite (MM) is a near-circular peraluminous monzogranite pluton occupying the entire 10 km² of Montecristo Island. Outcrops of country rock are scarce, and are mainly roof pendants of metagabbros and calcsilicate hornfels of the Apenninic ophiolite sequence. Emplacement of the pluton (Rb–Sr age=7·1±0·2 Ma), following the early Miocene onset of continental collision, occurred during an extensional phase which migrated eastward via a combined process of subduction–delamination. The MM rocks are strongly porphyritic, the assemblage being composed of alkali-feldspar, quartz, plagioclase (all occurring as mega- or phenocrysts), biotite and minor cordierite. Accessory minerals include tourmaline, apatite, zircon, ilmenite, allanite, monazite, rutile and hellandite. Reconstructed crystallization histories for the mineral phases reveal a polybaric crystallization starting at about 5 kb. Textural variations of MM occur in sharp contact with each other; darker types often form globular masses containing fewer megacrysts and more abundant mafic microgranular enclaves. Geochemical, isotopic and petrographic data indicate that the MM magma was produced by anatectic melting of an intermediate to deep pelitic crustal source. On the basis of the geochemical and mineralogical characteristics of the enclaves, modification of their parent magma occurred by crystal fractionation coupled with mixing and mingling of components from the MM magma. The limited geochemical variation in MM is interpreted as due to crystal fractionation processes during the magma's ascent. Younger porphyritic dykes with more potassic and alkaline affinities cut the pluton; these dykes are concentrated in a major fracture zone and are associated with contemporaneous pseudotachylites. © 1997 John Wiley & Sons, Ltd.  相似文献   

浆混花岗岩专题填图方法初探——以东昆仑加鲁河地区为例   总被引：1，自引：1，他引：0  

王连训  马昌前  熊富浩  王富康  郭富涛  刘敬 《地质通报》2017,36(11):1971-1986

东昆仑造山带花岗岩中广泛发育暗色微粒包体,含有丰富的壳幔岩浆混合作用的证据,被认为是研究岩浆混合作用的天然场所。适逢近阶段同源花岗岩谱系填图方案在造山带岩浆混合(浆混)花岗岩图区实践时深受质疑,本研究以东昆仑加鲁河地区浆混花岗岩为例,开展浆混花岗岩区专题填图试点工作,旨在探索一套适合浆混花岗岩填图的岩石单位划分方案。从野外地质、岩相学、岩石和矿物化学等不同角度论证了加鲁河花岗闪长岩及其内部包体形成于开放体系下的壳幔岩浆混合作用。在填图工作中,将图区内的岩浆岩划分为浆混花岗岩和非浆混花岗岩2个超单元。以岩浆混合作用为理论依据,将浆混花岗岩超单元划分为基性端元、酸性端元和浆混产物3个二级单位,对于2个端元岩石单位按照其矿物组成、结构构造等方面的差异(岩浆演化导致)再次划分最基本岩石单位——侵入体,对于浆混产物单位,建议可按照岩浆混合程度差异或者内部包体变化规律灵活划分基本岩石单位——浆混体。由此建立了一套可与同源花岗岩谱系单位相兼容的浆混花岗岩谱系单位划分方案,为岩浆混合花岗岩区开展填图工作提供了初步探索方案。  相似文献