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Mantle Driven Early Eocene Magmatic Flare-up of the Gangdese Arc, Tibet: A Case Study on the Nymo Intrusive Complex

Acta Geologica Sinica(English Edition) 2024年第4期98卷 878-903页

作者： MA Xuxuan Joseph GMEERT CAO Wenrong TIAN Zuolin LIU Dongliang XIONG Fahui LI Haibing Key laboratory of Continental Tectonics and Dynamics of Ministry of Natural Resources Institute of GeologyChinese Academy of Geological SciencesBeijing 100037China Jiangsu Donghai Continental Deep Borehole Crustal Activity National Observation and Research Station DonghaiJiangsu 222300China Department of Geological Sciences Neil Opdyke Paleomagnetic LaboratoryUniversity of Florida241 Williamson HallGainesvilleFL 32611USA Department of Geological Sciences and Engineering University of NevadaRenoMS-1721664 N.Virginia St.RenoNV 89557USA

Magmatic periodicity is recognized in continental arcs worldwide, but the mechanism responsible for punctuated arc magmatism is controversial. Continental arcs in the Trans-Himalayan orogenic system display episodic magmatism and the most voluminous flare-up in this system was in early Eocene during the transition from subduction to collision. The close association of the flare-up with collision is intriguing. Our study employs zircon Lu-Hf and bulk rock Sr-Nd isotopes, along with mineral geochemistry, to track the melt sources of the Nymo intrusive complex and the role of mantle magma during the early Eocene flare-up of the Gangdese arc, Tibet. The Nymo intrusive complex is composed of gabbronorite, diorite, quartz diorite, and granodiorite which define an arc-related calc-alkaline suite. Zircon U-Pb ages reveal that the complex was emplaced between ~50–47 Ma. Zircon Hf isotopes yield εHf(t) values of 8.2–13.1, while whole-rock Sr and Nd isotopes yield εNd(t) values of 2.7–6.5 indicative of magmatism dominated by melting of a juvenile mantle source with only minor crustal assimilation(~15%–25%) as indicated by assimilation and fractional crystallization modeling. Together with published data, the early Eocene magmatic flare-up was likely triggered by slab breakoff of subducted oceanic lithosphere at depths shallower than the overriding plate. The early Eocene magmatic flare-up may have contributed to crustal thickening of the Gangdese arc. This study provides important insights into the magmatic flare-up and its significant role in the generation of large batholiths during the transition from subduction to collision.

关键词： mantle magmatic flare-up subduction–collision transition Nymo intrusive complex Gangdese Tibet

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Low-latitude hydroclimate changes related to paleomagnetic variations during the Holocene in coastal southern China

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Frontiers of Earth Science 2024年第2期18卷 324-335页

作者： Tingwei ZHANG Xiaoqiang YANG Jian YIN Qiong CHEN Jianfang HU Lu WANG Mengshan JU Qiangqiang WANG School of Earth Science and Engineering/Guangdong Provincial Key Laboratory of Geodynamics and Geohazards/Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)Sun Yat-sen UniversityGuangzhou 510275China Institute of Cultural Heritage Shandong UniversityQingdao 266237China State Key laboratory of Organic Geochemistry Guangzhou Institute of GeochemistryChinese Academy of SciencesGuangzhou 510640China College of Urban and Environmental Sciences Peking UniversityBeijing 100871China Institute of Oceanology Chinese Academy of SciencesQingdao 266071China

The variations in precipitation have displayed a complex pattern in different regions since the *** formation processes may have a significant impact on precipitation,especially during the tropical marine processes and summer monsoon which convey abundant water vapor to coastal southern China and inland ***,we use two 7500 year sedimentary records from the Pearl River Delta and the closed Maar Lake,respectively,in coastal southern China to reconstruct the mid-to-late-Holocene humidity variability and explore its possible relationship with cloud cover modulated by the Earth’s magnetic fields(EMF).Our proxy records document an apparent increase in wetness in coastal southern China between 3.0 and 1.8 kyr *** apparent increase in humidity appears to be consistent with the lower virtual axial dipole moments and,in turn,with a lower *** correlation suggests that the EMF might have been superimposed on the weakened monsoon to regulate the mid-to-late-Holocene hydroclimate in coastal southern China through the medium of galactic cosmic rays,aerosols,and cloud ***,further investigations are needed to verify this interaction.

关键词： hydroclimate variations Earth’s magnetic field coastal southern China the Holocene epoch

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Neogene integrative stratigraphy,biotas,and paleogeographical evolution of the Qinghai-Tibetan Plateau and its surrounding areas

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Science China Earth Sciences 2024年第4期67卷 1326-1359页

作者： Tao DENG Xiaomin FANG Qiang LI Shiqi WANG Feixiang WU Sukuan HOU Jiao MA Qigao JIANGZUO Danhui SUN Yan ZHENG Qinqin SHI Boyang SUN Lu LI Key laboratory of Vertebrate Evolution and Human Origins Institute of Vertebrate Paleontology and PaleoanthropologyChinese Academy of SciencesBeijing 100044China CAS Center for Excellence in Life and Paleoenvironment Beijing 100044China University of Chinese Academy of Sciences Beijing 100049China CAS Center for Excellence in Tibetan Plateau Earth Sciences and Key laboratory of Continental Collision and Plateau Uplift Institute of Tibetan Plateau ResearchChinese Academy of SciencesBeijing 100101China Key laboratory of Orogenic Belts and Crustal Evolution School of Earth and Space SciencesPeking UniversityBeijing 100871China

The remarkable uplift of the Tibetan Plateau in the Neogene had great impacts on the climate and environment of East Asia and even the ***,establishment of the Neogene stratigraphic framework of the Tibetan Plateau is of great significance to research in various fields of *** on marine sediments,the international chronostratigraphic system of the Neogene is divided into six stages in the Miocene and two stages in the *** the beginning of the Cenozoic,the share of terrestrial strata on continents has increased *** the Neogene,it had far exceeded that of marine strata,and almost all deposits on the Tibetan Plateau and its surrounding areas were terrestrial *** China,the Miocene includes five stages and the Pliocene includes two *** for the Tunggurian of the Miocene,which has a lower boundary at 15 Ma,the other stages have the same paleomagnetic definitions and time intervals as the corresponding international marine *** fossils play a very important role in the division and correlation of Cenozoic terrestrial strata,and rodent,carnivore,proboscidean,perissodactyl and artiodactyl fossils are especially important in Neogene terrestrial *** are many basins with well-exposed strata and abundant mammalian fossils in the Tibetan *** lower boundary stratotype sections of the Neogene Xiejian and Bahean stages are located respectively in the Xining and Linxia basins,and there are precise paleomagnetic dates in coordination with mammalian *** lower boundary stratotypes of other stages can also be effectively determined in the Tibetan *** first appearing mammalian genera in East Asia also appeared in the Tibetan Plateau and its surrounding areas,especially in the Linxia Basin on the northeast margin and in the Siwaliks on the southwest *** them,Prodeinotherium first appeared at the bottom of the Miocene in the Siwaliks,and the earliest Hipparion of the Old

关键词： Tibetan Plateau Neogene Terrestrial stratum Mammalian fossil Paleomagnetism

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The incorporation of thermal methods in mineral magnetism of loess-paleosol sequences: a brief overview

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Chinese Science Bulletin 1999年第S1期44卷 53-63页

作者： A.J.VanVelzen M.J.Dekkers paleomagnetic laboratory fort hoofddijk Faculty of Earth Sciences Budapestlaan 17 3584 CD Utrecht The Netherlands

The advantages of thermal methods for mineral-magnetic research of loess/paleosolsequences are illustrated in an introductory overview. When applying thermal methods, magnetiteand maghemite can be distinguished, something which is difficult with field-dependentmeasurements at room temperature. Also, variable low-temperature oxidation that is related toclimate may be quantified. Thirdly, grain-size estimates pertaining to the whole superparamagneticrange can be inferred from LT warming experiments and to a lesser extent from variable chemicalalteration during heating. Application of mineral-magnetic techniques may lead to thedevelopment of quantifiable proxy parameters for paleoclimate.

关键词： Magnetic minerals loess paleosol pedogenic processes Curie temperature

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Avalonia,get bent!–Paleomagnetism from SW Iberia confirms the Greater Cantabrian Orocline

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Geoscience Frontiers 2021年第2期12卷 805-825页

作者： Bruno Daniel Leite Mendes Daniel Pastor-Galan Mark J.Dekkers Wout Krijgsman paleomagnetic laboratory fort hoofddijk Department of Earth SciencesUtrecht UniversityBudapestlaan 173584CDthe Netherlands Frontier Research Institute for Interdisciplinary Sciences Tohoku UniversityJapan Department Earth Science Tohoku UniversityJapan Center for North East Asia Studies Tohoku University980-857641 KawauchiAoba-kuSendaiMiyagiJapan

The amalgamation of Pangea formed the contorted Variscan-Alleghanian orogen,suturing Gondwana and Laurussia during the *** all swirls of this orogen,a double curve in Iberia stands out,the coupled Cantabrian Orocline and Central Iberian *** Cantabrian Orocline formed at ca.315–290 Ma subsequent to the Variscan *** formation mechanism of the Cantabrian Orocline is disputed,the most commonly proposed mechanisms include either(1)that south-westernmost Iberia would be an Avalonian(Laurussian)indenter or(2)that the stress field changed,buckling the *** contrast,the geometry and kinematics of the Central Iberian curve are largely *** some authors defend both curvatures are genetically linked,others support they are distinct and formed at different *** uncertainty adds an extra layer of complexity to our understanding of the final stages of Pangea’s *** solve these issues,we study the late Carboniferous–early Permian vertical-axis rotations of SW Iberia with *** results show up to 70counterclockwise vertical-axis rotations during late Carboniferous times,concurring with the anticipated kinematics if SW Iberia was part of the southern limb of the Cantabrian *** results do not allow the necessary penecontemporaneous clockwise rotations in Central Iberia to support a concomitant formation of both Cantabrian and Central Iberian *** coherent rotation of both Gondwanan and Avalonian pieces of SW Iberia discards the Laurussian indenter hypothesis as a formation mechanism of the Cantabrian Orocline and confirms the Greater Cantabrian Orocline *** Greater Cantabrian Orocline likely formed as a consequence of a change in the stress field during the late Carboniferous and extended beyond the Rheic Ocean suture affecting the margins of both Laurussia and Gondwana.

关键词： Pangea Variscan orogeny Greater Cantabrian Orocline Paleomagnetism Central Iberian curve

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