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Petrological and geochemical characteristics of mafic rocks from the Neoproterozoic Sugetbrak Formation in the northwestern Tarim Block,China

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China Geology 2023年第1期6卷 85-99页

作者： Hong-zhe Xie Xiang-kun Zhu Xun Wang Yuan He Wei-bing Shen MNR Key Laboratory of Isotope Geology MNR Key Laboratory of Deep-Earth DynamicsInstitute of GeologyChinese Academy of Geological SciencesBeijing 100037China

The Neoproterozoic Sugetbrak Formation in the Aksu area,which is located at the northwest margin of Tarim Block,comprises mafic rocks and provides key records of the evolution of the Rodinia ***,the genetic relationship among these mafic rocks exposed in different geographical sections are still *** this study,the petrology,geochemistry,and Sr-Nd-Pb isotope geochemistry of the mafic rocks exposed in the Aksu-Wushi and Yuermeinark areas have been studied in some detail along three *** authors found that the mafic rocks in these three typical sections were mainly composed of pyroxene and plagioclase,containing a small amount of Fe-Ti oxides and with typical diabasic *** the mafic rocks in this region also showed similar geochemical *** were characterised by high TiO_(2)contents(1.47%–3.59%)and low MgO(3.52%–7.88%),K_(2)O(0.12%–1.21%).Large ionic lithophile elements(LILEs)(Rb,Sr,and Cs)were significantly ***,high field strength elements(HFSEs)were relatively *** the samples,light rare earth elements(LREEs)were enriched,while heavy rare earth elements(HREEs)were *** on the Zr/Nb,Nb/Y,and Zr/TiO_(2)ratios,the Aksu mafic rocks belong to a series of sub-alkaline and alkaline transitional *** mafic rocks along the three typical sections showed similar initial values of^(87)Sr/^(86)Sr(I_(Sr))(0.7052–0.7097)and ε_(Nd)(t)(–0.70 to–5.35),while the Pb isotopic compositions with^(206)Pb/^(204)Pb,^(207)Pb/^(204)Pb and^(208)Pb/^(204)Pb values of 16.908–17.982,15.487–15.721,37.276–38.603,*** of the samples plot into the area near EM-Ⅰ,indicating that the magma of the mafic rocks might have derived from a relatively enriched mantle with some crustal materials *** geochemical element characteristics of most samples showed typical OIB-type geochemical characteristics indicating that the source region had received metasomatism of recycled *** with the

关键词： mafic rocks Sugetbrak Formation Rodinia supercotinent Neoproterozoic Sr-Nd-Pb isotopes Mantle plume Geological survey engineering Tarim Block Xinjiang

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Geodynamic evolution of the Tethyan lithosphere as recorded in the Spontang Ophiolite,South Ladakh ophiolites(NW Himalaya,India)

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Geoscience Frontiers 2022年第1期13卷 326-349页

作者： Mallika K.Jonnalagadda Mathieu Benoit Shivani Harshe Romain Tilhac Raymond A.Duraiswami Michel Grégoire Nitin R.Karmalkar Interdisciplinary School of Science Savitribai Phule Pune UniversityPune 411007India Department of Geology Savitribai Phule Pune UniversityPune 411007India Géosciences Environnement Toulouse CNRS-CNES-IRD-UniversitéPaul SabatierObservatoire Midi Pyrénées31400 ToulouseFrance Instituto Andaluz de Ciencias de la Tierra(IACT) CSIC–Universidad de Granada18100 ArmillaGranadaSpain Vice-Chancellor’s Office Savitribai Phule Pune UniversityPune 411007India

The Spontang Ophiolite complex represents the most complete ophiolite sequence amongst the South Ladakh ophiolites and comprises mantle rocks(depleted harzburgites,dunites and minor lherzolites)as well as crustal rocks(basalt,isotropic gabbros,layered gabbros etc.).In the present study,detailed geochemistry(whole rock as well as mineral chemistry)and Sr-Nd isotopic analyses of thirty-six ultramaficmafic samples have been attempted to constraint the evolution and petrogenetic history of the Tethyan oceanic ***,trace-element and REE patterns of the peridotites and their minerals indicate that the lherzolites experienced lower degrees of partial melting resembling abyssal peridotites(at higher temperatures,TREE=$1216℃)than the harzburgites(6%–8%versus 15%–17%).Elevated eNd(t)and variable^(87) Sr/^(86) Sr(t)ratios along with REE patterns suggest that the Spontang mafic rocks display N-MORB affinity with negligible participation of oceanic sediments in their genesis are originated from a depleted upper mantle with little contribution from subduction-related ***-type Neotethyan oceanic crust is associated with the earliest phase of subduction(of older Jurassic age)through which a younger intra-oceanic island arc(Spong arc)subsequently *** REE display typical U-shaped patterns,suggesting that these rocks have been metasomatized by LREE-enriched *** the other side,mafic rocks are characterized by heterogeneous(Nb/La)PMand(Hf/Sm)PMand relatively homogeneous eNd(t),indicating interaction of subduction-related melts with the upper mantle during the initiation of subduction,in Early Cretaceous times.

关键词： Peridotites mafic rocks Partial melting Metasomatism Ladakh

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Geochronological Framework and Geodynamic Implications of mafic Magmatism in the Liaodong Peninsula and Adjacent Regions,North China Craton

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Acta Geologica Sinica(English Edition) 2016年第1期90卷 138-152页

作者： LI Zhuang CHEN Bin WANG Jialin The Key Laboratory of Orogenic Belts and Crustal Evolution Ministry of EducationSchool of Earth and Space SciencesPeking University School of Resources and Environmental Engineering Hefei University of Technology

mafic rocks are widespread on the Liaodong Peninsula and adjacent regions of the North China Craton. The majority of this magmatism was originally thought to have occurred during the Pre-Sinian, although the precise geochronological framework of this magmatism was unclear. Here, we present the results of more than 60 U-Pb analyses of samples performed over the past decade, with the aim of determining the spatial and temporal distribution of mafic magmatism in this area. These data indicate that Paleoproterozoic-Mesoproterozoic mafic rocks are not as widely distributed as previously thought. The combined geochronological data enabled the subdivision of the mafic magmatism into six episodes that occurred during the middle Paleoproterozoic, the late Paleoproterozoic, the Mesoproterozoic, the Late Triassic, the Middle Jurassic, and the Early Cretaceous. The middle Paleoproterozoic （2.1-2.2 Ga） mafic rocks formed in a subduction-related setting and were subsequently metamorphosed during a ca. 1.9 Ga arc-continent collision event. The late Paleoproterozoic （ca. 1.87-1.82 Ga） bimodal igneous rocks mark the end of a Paleoproterozoic tectono- thermal event, whereas Mesoproterozoic mafic dike swarms record global-scale Mesoproterozoic rifting associated with the final breakup of the Columbia supercontinent. The Late Triassic mafic magmatism is part of a Late Triassic magmatic belt that was generated by post-coilisional extension. The Middle Jurassic mafic dikes formed in a compressive tectonic setting, and the Early Cretaceous bimodal igneous rocks formed in an extensional setting similar to a back-arc basin. These latter two periods of magmatism were possibly related to subduction of the Paleo-Pacific plate.

关键词： mafic rocks geochronology Liaodong Peninsula tectonic setting

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Record of Early Tonian mafic magmatism in the central Espinhaco(Brazil):New insights for break-up of the Neoproterozoic landmass ancestor of Sao Francisco-Congo paleocontinent

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Geoscience Frontiers 2020年第6期11卷 2323-2337页

作者： Helen F.Moreira AndréDanderfer Alice F.O.Costa Samuel M.Bersan Cristiano C.Lana Gláucia N.Queiroga Post Graduate Program of Department of Geology Mine SchoolFederal University of Ouro PretoBrazil Department of Geology Mine SchoolFederal University of Ouro PretoBrazil

Petrological characterization,U-Pb geochronology,Lu-Hf analyses and major and trace element data from mafic intrusions in the Central Espinhaco(central portion of the Brazilian shield)are used here to investigate the geological significance of the Early Neoproterozoic magmatism in the context of the Sao Francisco-Congo *** mafic bodies are represented by medium to coarse-grained metagabbros with plagioclase,amphibole and *** U-Pb isotopic data from two samples yielded weighted mean 206pb/238U ages of 895±3.4 Ma(MSWD=1.7)and 896±2.4 Ma(MSWD=0.64),regarded as the best estimates for the crystallization age of these mafic *** and trace element data(including REEs)show that the gabbros originated from a subalkaline tholeiitic magma,typical of intraplate *** rocks are slightly enriched in LREEs and LILEs and depleted in *** new isotope and geochemical data,along with regional knowledge,indicate that these metagabbros mark the beginning of an important Tonian-age extensional tectonic event of the landmass of which the Sao Francisco-Congo paleocontinent was part(Rodinia supercontinent or Central African block?).We furthermore suggest that these rocks belong to a prominent suite of Tonian-age mafic rocks that mark a diachronic breakup attempt of this landmass which may have occurred from south to north along the Espinhaco mountain range.

关键词： mafic rocks Espinhaco basin Sao Francisco-Congo paleocontinent Tonian rifting U–Pb geochronology

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Geochronology and petrogenesis of the mafic dykes from the Purang ophiolite:Implications for evolution of the western Yarlung-Tsangpo suture zone,southwestern Tibet

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Geoscience Frontiers 2020年第1期11卷 277-292页

作者： Fahui Xiong Yuanku Meng Jingsui Yang Zhao Liu Xiangzhen Xu Alireza Eslami Ran Zhang Shandong Provincial Key Laboratory of Depositional Mineralization and Sedimentary Minerals College of Earth Science and EngineeringShandong University of Science and TechnologyQingdao 266590China Center for Advanced Research on the Mantle(CARMA) Key Laboratory of Deep-Earth Dynamics of Ministry of Land and ResourcesInstitute of GeologyChinese Academy of Geological SciencesBeijing 100037China Institute of Mineral Resources Chinese Academy of Geological SciencesBeijing 100037China School of Geology College of ScienceUniversity of TehranTehran ***Iran

The>2000 km Indus-Yarlung Tsangpo suture zone(IYSZ)is composed of the Neo-tethys oceanic remnants,flysch units and related continental rocks,which has been regarded as the boundary between the Eurasian and Indian *** the ophiolitic complexes,the Purang ophiolite is the biggest massif in the IYSZ,and many studies have been conducted on this ***,previous studies have mainly focused on harzburgite,clinopyroxenite and *** observations show that mafic dykes were emplaced within the Purang ***,petrogenetic evolutions of those mafic dykes are poorly *** this study,we present new LA-ICP-MS zircon U-Pb dating results,whole-rock geochemistry and Sr-Nd-Hf isotope analyses for microgabbro,gabbro and dolerite dykes from the Purang ophiolite of the southwestern IYSZ,*** samples yielded zircon U-Pb ages of144.2±2.1 Ma.127.9±2.3 Ma and 126.5±0.42 Ma,suggesting two different phases of magmatic activities ***-rock geochemical results suggest that the gabbro samples show alkaline features marked by enrichments of light rare earth elements(LREE)and large-ion lithophile elements(LILE),as well as Nb-Ta elements,suggesting an oceanic island basalt-like(OIB-like)geochemical ***,the dolerite and microgabbro samples demonstrate sub-alkaline characteristics with normal mid-oceanic ridge basalt-like(N-MORB-like)geochemical *** distinct mafic dykes show significant Rb element *** geochemical data and Sr-Nd-Hf isotopic features suggest that the microgabbro and gabbro rocks were derived from a depleted mantle that had been metasomatized by partial melts of sediments and enriched slab-derived *** dolerite was also originated from a depleted mantle marked by significantly depleted Sr-Nd-Hf compositions,which was not influenced by enriched slab-derived fluids and sediments contamination during subsequent *** isotope and geochemical data and tectonic diagrams sugges

关键词： Isotope geochemistry mafic rocks Purang ophiolite Yarlung Tsangpo suture zone

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The Pan-African Ophiolites and Related Mineralization in Egypt

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Acta Geologica Sinica(English Edition) 2015年第A2期89卷 65-68页

作者： MOHAMED METWALY Abu Anbar Geology Department Faculty of ScienceTanta University

Precambrian ophiolites are abundant in the Arabian- Nubian Shield of NE Africa and Arabia and range in age fronl 690 to 890 Ma. In Egypt, they are widely distributed in the central and southern Eastern Desert and occu... 详细信息

关键词： RESEARCH Ultrabasic rocks mafic rocks Igneous rocks Ophiolites Mineralization (Geology)

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Geochronology and Geochemistry of the Triassic mafic Complexes from the Western Garzê-Litang Ophiolitic Mélange and Implications for the Melt Evolution of a Continental Margin

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Acta Geologica Sinica(English Edition) 2015年第A2期89卷 50-51页

作者： LIU Bin MA Changqian ZHANG Xin GUO Pan ZHANG Hang XIONG Fuhao State Key Laboratory of Geological Processes and Mineral Resources China University ofGeosciences Wuhan430074 China Faculty of Earth Sciences China University of Geosciences Wuhan 430074 China

There is a general consensus that most ophiolites on the earth formed above a subduction zone and they often display a characteristic, sequential evolution of MORB to island arc tholeiities （IAT） to bonnites （Dilek et al., 2010, 2009; Pearce et al., 2003）. However, ophiolites occurred in a continental margin are very rare and usually have more complicated, irregular components, such as N-MORB,

关键词： RESEARCH mafic rocks Ophiolites Mid-ocean ridges Geological time Geochemistry

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