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Late Triassic Magma Mixing and fractional crystallization in the Qingchengzi Orefield,Eastern Liaoning Province:Regional Petrogenetic and Metallogenic Implications

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Journal of Earth Science 2021年第1期32卷 144-157页

作者： Hongjing Xie Yuwang Wang Dedong Li Guochao Zhou Zhichao Zhang Beijing Institute of Geology for Mineral Resources Beijing 100012China Deep Exploration Technic Center for Non-Ferrous Mines Beijing 100012China School of Earth Sciences and Resources China University of GeosciencesBeijing 100083China

The Qingchengzi orefield is an important Pb-Zn-Au-Ag polymetallic orefield in NE *** Indosinian magmatism has formed the Shuangdinggou batholith and the Xinling stock,as well as dikes of quartz monzonite porphyry and *** to petrographic characteristics,the Shuangdinggou intrusion can be divided into the main suite and the central *** U-Pb dat-ing yielded crystallization ages of 215.0-220.9 Ma for these various Qingchengzi magmatic units,which are within analytical error and represent coeval *** Shuangdinggou main suite contains abundant mafic microgranular enclaves(MMEs)and shows features of magma ***,the major oxide contents of the MMEs and their quartz monzonite host show well-defined linear frac-tionation *** REE and trace element patterns of the MMEs and their host are similar,which demonstrates certain degree of geochemical homogenization between the two during magma *** Shuangdinggou main suite shares similar geochemical characteristics with typical high Ba-Sr gra-nites(Ba=1082 ppm-2051 ppm,Sr=803 ppm-886 ppm),and was likely originated from the mixing between a melt derived from partial melting of the thickened lower crust and the enriched *** central suite was likely formed by fractional crystallization of the main-suite *** Xinling in-trusion may represent a branch of the Shuangdinggou intrusion and has the same genesis as the central *** quartz monzonite porphyries geochemically mimic the Shuangdinggou main suite,and may also be an epioic facies of the Shuangdinggou *** MMEs and lamprophyres may have been derived from incomplete magma *** of the Pb-Zn and Au-Ag deposits in the Qing-chengzi orefield may have been related to the granite/quartz monzonite porphyries near the Shuangdinggou intrusion,which were formed by magma mixing and fractional crystallization.

关键词： Qingchengzi orefield Shuangdinggou intrusion magma mixing mafic microgranular enclave(MME) fractional crystallization

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Large-scale liquid immiscibility and fractional crystallization in the1780 Ma Taihang dyke swarm:Implications for genesis of the bimodal Xiong'er volcanic province

Large-scale liquid immiscibility and fractional crystallizat...

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中国科学院地质与地球物理研究所2015年度（第15届）学术年会

作者： Peng Peng Xinping Wang Yong Lai Chong Wang Brian F.Windley State Key Laboratory of Lithospheric Evolution Institute of Geology and GeophysicsChinese Academy of Sciences School of Earth and Space Sciences Peking University Department of Geology University of Leicester

Immiscibility is a potential mechanism for the formation of high-Fe–Ti–P rocks;however,whether large-scale segregation and eruption of high-Si lavas can occur in nature has yet to be *** this study,we investigate the possibility of immiscibility between the cogenetic 1780 Ma high-Fe–Ti–P-bearing Taihang dykes and the‘bimodal’Xiong’er volcanics in North *** compositions of silicate melt inclusions in plagioclase megacrysts of the dykes provide a new approach to obtain the primary *** and bulk-rock compositions reveal that large compositional variations in the dykes are the result of plagioclase-and clinopyroxene-dominated fractional crystallization and of density-driven mineral sorting,which together caused the liquids to be poor in Ca–Al but rich in Fe–Ti–P–K,and thus chemically *** interstitial granophyric and ilmeniterich intergrowths and reactive microstructures especially olivine coronas in the dykes,and Si–/Fe–Ti-rich globules in the volcanics,provide petrographic evidence for the presence of two coeval,coexisting liquids in equilibrium separated by a miscibility gap,and thus for immiscibility and segregation/*** fractional crystallization and subsequent segregation were responsible for the compositional diversity of the Taihang dykes and also of the‘bimodal’Xiong’er ***,the dacite and rhyolite lavas are potentially the high-Si counterparts of the high-Ti dykes,and the basalt and andesite lavas are the erupted equivalents of the relatively low-Ti *** is likely that the sustained plagioclase-and clinopyroxene-dominated fractional crystallization,and the enhanced f Owere responsible for the *** segregation probably took place during the ascent of the liquid in the pumping system(feeder dykes).This likely represents one natural example of crust-scale immiscibility from which many high-Ti dykes and silicic lavas(/3 volume of the Xiong’er volcanic province)were segregated and subs

关键词： Large-scale immiscibility fractional crystallization High-Fe–Ti–P rocks Taihang dyke swarm Xiong’er volcanic province Melt inclusion

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Origin of the Volcanic Rocks Erupted in the Eastern Manus Basin：Basaltic Andesite-Andesite-Dacite Associations

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Journal of Ocean University of China 2017年第3期16卷 389-402页

作者： MA Yao ZENG Zhigang CHEN Shuai YIN Xuebo WANG Xiaoyuan Seafloor Hydrothermal Activity Laboratory of the Key Laboratory of Marine Geology and Environment Institute of Oceanology Chinese Academy of Sciences Qingdao 266071 P. R. China University of Chinese Academy of Sciences Beijing 100049 P. R. China Laboratory for Marine Mineral Resources Qingdao National Laboratory for Marine Science and Technology Qingdao 266071 P. R. China

There has been much recent interest in the origin of intermediate lava and several hypotheses are: 1) direct melting of the mantle under water-saturated conditions, 2) partial melting of altered crust, 3) fractional crystallization of parent magma, and 4) magma mixing of mafic magmas with dacitic/rhyolitic magmas. Volcanic rocks series ranging from basaltic andesite to dacite(SiO_2 ranges from 53.8 to 63.0 wt.%) from the eastern Manus Basin were detected for major and trace element compositions to understand their origin. Low H_2O contents, positive correlations of La-SiO_2 and Yb-SiO_2, oxygen isotope data and the indistinct change of trace element concentrations in oscillatory zoning of plagioclase phenocrysts rule out the models in which silicic lava results from direct melting of hydrous mantle, partial melting of altered oceanic crust or gabbros, and magma mixing, respectively. Besides, the geochemical data of whole rock and melt inclusions indicate that fractional crystallization plays a dominant role in generating the intermediate lava with subduction features.

关键词： Eastern Manus Basin fractional crystallization volcanic rocks

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Geochemical and Sr-Nd-Pb isotopic compositions of volcanic rocks from the Iheya Ridge,the middle Okinawa Trough：implications for petrogenesis and a mantle source

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Acta Oceanologica Sinica 2018年第1期37卷 73-88页

作者： LI Xiaohui ZENG Zhigang CHEN Shuai MA Yao YANG Huixin ZHANG Yuxiang CHEN Zuxing Key Laboratory of Marine Geology and Environment Institute of Oceanology Chinese Academy of Sciences Qingdao 266071 China University of Chinese Academy of Sciences Beijing 100049 China Laboratory for Marine Mineral Resources Qingdao National Laboratory for Marine Science and Technology Qingdao 266071 China

As an active back-arc basin, the Okinawa Trough is located in the southeastern region of the East China Sea shelf and is strongly influenced by the subduction of the Philippine Sea Plate. Major element, trace element and Sr-NdPb isotopic composition data are presented for volcanic rocks from the Iheya Ridge（IR）, the middle Okinawa Trough. The IR rocks record large variations in major elements and range from basalts to rhyolites. Similar trace element distribution characteristics together with small variations in ^87Sr/^86Sr（0.703 862–0.704 884）, ^144Nd/^143Nd（0.512 763–0.512 880） and Pb isotopic ratios, demonstrate that the IR rocks are derived from a similar magma source. The fractional crystallization of olivine, clinopyroxene, plagioclase, and amphibole, as well as accessory minerals, can reasonably explain the compositional variations of these IR rocks. The simulations suggest that approximately 60% and 75% fractionation of an evolved basaltic magma can produce trace element compositions similar to those of the intermediate rocks and acid rocks, respectively. The analysis of their Sr-Nd-Pb isotopic content ratios suggest that the source of the rocks from the IR is close to the depleted mantle（DM） but extends to the enriched mantle（EMII）, indicating that the mantle source of these rocks is a mixture between the DM and EMII end members. The simulations show that the source of the IR volcanic rocks can be best interpreted as the result of the mixing of approximately 0.8%–2.0% subduction sediment components and 98.0%–99.2% mantlederived melts.

关键词： basic to intermediate-acid rocks fractional crystallization subduction sediment components Iheya Ridge Okinawa Trough

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Geochemical Characteristics of a Carbonatite Dyke Rich in Rare Earths from Bayan Obo, China

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Journal of Rare Earths 2000年第1期18卷 1-8页

作者：杨学明杨晓勇陈天虎张培善陶克捷 Department of Earth and Space Sciences University of Science and Technology of China Hefei 230026 China Department of Resources and Environment Sciences Hefei University of Technology Hefei 230009 China Institute of Geology Chinese Academy of Sciences Beijing 100029 China Department of Geology Southampton University United Kingdom Natural History Museum London SW7 5BD United Kingdom

The whole-rock geochemistry of a rare earths rich carbonatite dykes that locates at Dulahala and lies 3 km north-east to the East Ore body of the giant Bayan Obo RE-Nb-Fe deposit was analysed. The dyke cuts cross H1 coarse quartz sandstone and H2 fine quartzite of the Proterozoic Bayan Obo group. RE content in the dyke varies greatly up to 20% (mass fraction), which comprises rich RE ores. Light RE in carbonatites are extremely enriched and strongly fractionated relative to heavy RE, but no Eu anomaly. The carbonatite may be produced by mechanisms as follows: the carbonatite mana is directly formed by very low degree (F fractional crystallization, which makes RE further concentrated in carbonatite. The RE patterns and spider diagrams of the carbonatite are identical to those fine-grained dolomite marble that is the ore-host rock for the Bayan Obo deposit. However, the carbonatite is calcic, which is different from the fine-grained dolomite marble in major element geochemistry. The difference is suggested to be resulted from that the carbonatite dyke is not affected by a large scale dolomitization, while the fine-grained dolomite marble might be the product of dolomitized carbonatite intrusive body that might set up a hydrothermal system in the region, which transported Mg from the Bayan Obo sediments, especially form the shales to the carbonatite intrusion.

关键词： rare earths carbonatite fractional crystallization hydrothermal fluid Bayan Obo

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Highly fractionated granites:Recognition and research

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Science China Earth Sciences 2017年第7期60卷 1201-1219页

作者： WU FuYuan LIU XiaoChi JI WeiQiang WANG JiaMin YANG Lei State Key Laboratory of Lithospheric Evolution Institute of Geology and Geophysics Chinese Academy of Sciences Beijing 100029 China Chinese Academy of Sciences Center for Excellence in Tibetan Plateau Earth Sciences Beijing 100101 China College of Earth Sciences University of Chinese Academy of Sciences Beijing 100049 China

Granite is one of the most important components of the continental crust on our Earth; it thus has been an enduring studied subject in geology. According to present knowledge, granite shows a great deal of heterogeneity in terms of its texture,structure, mineral species and geochemical compositions at different scales from small dike to large batholith. However, the reasons for these variations are not well understood although numerous interpretations have been proposed. The key point of this debate is whether granitic magma can be effectively differentiated through fractional crystallization, and, if so, what kind of crystallization occurred during the magmatic evolution. Although granitic magma has high viscosity because of its elevated SiO2 content, we agree that fractional crystallization is effectively processed during its evolution based on the evidence from field investigation,mineral species and its chemical variations, and geochemical compositions. These data indicate that crystal settling by gravitation is not the only mechanism dominating granitic differentiation. On the contrary, flow segregation or dynamic sorting may be more important. Accordingly, granite can be divided into unfractionated, fractionated(including weakly fractionated and highly fractionated) and cumulated types, according to the differentiation degree. Highly fractionated granitic magmas are generally high in primary temperature or high with various volatiles during the later stage, which make the fractional crystallization much easier than the common granitic melts. In addition, effective magmatic differentiation can be also expected when the magma emplaced along a large scale of extensional structure. Highly fractionated granitic magma is easily contaminated by country rocks due to its relatively prolonged crystallization time. Thus, granites do not always reflect the characteristics of the source areas and the physical and chemical conditions of the primary magma. We proposed that h

关键词： fractional crystallization Accumulation Highly fractionated granite Granitic magma Continental crustal evolution

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Accretion Processes of Oceanic Crust in Slow-spreading Ridges:Plagiogranite Perspective of the Xigaze Ophiolite,South Tibet

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Acta Geologica Sinica(English Edition) 2022年第6期96卷 1945-1959页

作者： LI Yuan LI Ruibao YANG Shengbiao ZHANG Jian YANG Jingsui Institute of Geology Chinese Academy of Geological SciencesBeijing 100037China School of Earth Sciences and Resources Chang’an UniversityXi’an 710054China Tianjin Institute of Geology and Mineral Resources Tianjing 300170China School of Earth Sciences and Engineering Nanjing UniversityNanjing 210023China

Structural and petrological data suggest that the Xigaze ophiolite from the Yarlung Zangbo Suture Zone(YZSZ)in south Tibet was a typical slow-spreading ridge.A new field,geochemical,mineral,and U-Pb zircon dataset of plagiogranite intrusions were used to constrain the dynamic processes of oceanic accretion in this slow-spreading *** mainly occur as dykes or intrusions intruded into the whole sequence of the ophiolite and have a similar orientation to the dolerite dykes developed in the late stage of detachment faulting.U-Pb zircon ages of 122–123 Ma were obtained for two types of plagiogranites and associated dolerite *** geochemical and mineralogical examinations suggest that the plagiogranites are the product of low-pressure(2–3 kbar)fractional crystallization of midocean ridge basalt-like magma and unlikely to have been derived from the partial melting of hydrous gabbroic *** complex cross-cut relationship between the plagiogranites and ophiolite sequence reflects that they are controlled by small discontinued melt lenses rather than a big magma chamber under the ridge axis and reveals multiple injections during the oceanic crust *** formation of plagiogranites possibly reflects the complex characteristic of oceanic accretion at slow-spreading ridges,time-dependent on structural(external)and magmatic(internal)processes.

关键词： Xigaze ophiolite plagiogranite fractional crystallization multiple magma injection ocean-continent transition zone

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Was the Panzhihua Large Fe-Ti Oxide Deposit,SW China,Formed by Silicate Immiscibility?

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Acta Geologica Sinica(English Edition) 2023年第5期97卷 1451-1461页

作者： DING Xiangli CHEN Xuanhua SHAO Zhaogang Chinese Academy of Geological Sciences Beijing 100037China

The Panzhihua mafic intrusion,which hosts a world-class Fe-Ti-V ore deposit,is in the western Emeishan region,SW *** formation age(~260 Ma),and Sr and Nd isotopes indicate that the Panzhihua intrusion is part of the Emeishan large igneous province and has little crustal *** assess ore genesis of the Panzhihua Fe-Ti-V ore deposit,two different models have been provided to explain the formation,namely silicate immiscibility and normal fractional *** immiscibility occurring around 1,000℃at the late stage of basaltic magma evolution argues against the silicate immiscibility ***-hosted melt inclusion research indicates that silicate immiscibility occurred at the late stage of Panzhihua magma evolution,which may not have offered potential to form such large ore deposits as ***,continuous compositional variations of the Panzhihua intrusion and calculations using thermodynamic modelling software support the hypothesis that the Panzhihua deposit was formed by normal fractional *** trace element patterns of the Panzhihua intrusion and nearby felsic rocks also coincide with the fractional crystallization *** fractional crystallization of high-Ti basaltic magma played a key role in the formation of the Panzhihua Fe-Ti-V ore deposit.

关键词： liquid immiscibility fractional crystallization mafic intrusion Fe-Ti oxide deposit Panzhihua

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New insights into the origin of the bimodal volcanism in the middle Okinawa Trough： not a basalt-rhyolite differentiation process

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Frontiers of Earth Science 2018年第2期12卷 325-338页

作者： Yuxiang ZHANG Zhigang ZENG Shuai CHEN Xiaoyuan WANG Xuebo YIN Seafloor Hydrothermal Activity Laboratory of the Key Laboratory of Marine Geology and Environment Institute of Oceanology Chinese Academy of Sciences Qingdao 266071 China Laboratory for Marine Mineral Resources Qingdao National Laboratory for Marine Science and Technology Qingdao 266071 China University of Chinese Academy of Sciences Beijing 100049 China

In the middle Okinawa Trough （MOT）,rhyolites have been typically considered as products ofcrystallization differentiation of basaltic magma as afeature of bimodal volcanism. However, the evidence isinsufficient. This paper compared chemical trends ofvolcanic rocks from the MOT with fractional crystal-lization simulation models and experimental results andutilized trace element modeling combined with Rayleighfractionation calculations to re-examine fractional crystal-lization processes in generating rhyolites. Both qualitativeand quantitative studies indicate that andesites, rather thanrhyolites, originate by fractional crystallization frombasalts in the MOT. Furthermore, we established twobatch-melting models for the MOT rhyolites and proposedthat type 1 rhyolites are produced by remelting of andesiteswith amphiboles in the residue, while type 2 rhyolites arederived from remelting of andesites without residualamphiboles. It is difficult to produce melts with a SiO2content ranging from 62% to 68% either by magmaticdifferentiation from basalts or by remelting of andesites,and this difficulty might help account for the compositionalgap （Daly gap） for bimodal volcanism in the OkinawaTrough.

关键词： Okinawa Trough rhyolite andesite remelting fractional crystallization

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The influence of fractionation of REE-enriched minerals on the zircon partition coefficients

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Geoscience Frontiers 2021年第3期12卷 249-258页

作者： Shihua Zhong Sanzhong Li Reimar Seltmann Zhiqing Lai Jie Zhou Frontiers Science Center for Deep Ocean Multispheres and Earth System Key Lab of Submarine Geosciences and Prospecting TechniquesMOE and College of Marine GeosciencesOcean University of ChinaQingdao 266100China Laboratory for Marine Mineral Resources Qingdao National Laboratory for Marine Science and TechnologyQingdao 266100China Center for Russian and Central EurAsian Mineral Studies Department of Earth SciencesNatural History MuseumLondon SW75BDUK

Zircon is widely used to simulate melt generation,migration and evolution within the crust and *** achievable performance of melt modelling generally depends on the availability of reliable trace element partition coefficients(D).However,a large range of D_(REE) values for zircon from natural samples and experimental studies has been reported,with values spanning up to 3 orders of ***,a gap of knowledge on this variability is *** this study we model the crystallization processes of common REE-bearing minerals from granitic melts and show that the measured zircon D_(REE) would be elevated if there is crystallization of REE-enriched minerals subsequent to ***,compared to zircon D_(REE) values measured from experimental studies,this mechanism appears to have a less significant influence on those from natural granite samples since the quantity of crystallized REE-enriched minerals is very low in natural magmatic systems and/or most of them crystallize prior to *** with recently published studies,this work supports that analysis of natural zircon/host groundmass pairs provides more robust D_(REE) values applicable to natural systems than those measured from experimental studies,which can be used to constrain the provenance of detrital zircons.

关键词： Rayleigh fractionation Partition coefficient fractional crystallization REE Zircon

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