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Evolution of Mount Cameroon volcanism: Geochemistry, mineral chemistry and radiogenic isotopes(Pb, Sr, Nd)

Geoscience Frontiers 2020年第6期11卷 2157-2168页

作者： Emmanuel Wenjeh Wembenyui Kenneth D.Collerson Jian-xin Zhao School of Earth and Environmental Sciences The University of QueenslandSt.Lucia CampusQLD4072BrisbaneAustralia Institute for Geological and Mining Research(IRGM)//Hydrological Research Centre Cameroon Ministry of Scientific Research and InnovationNkolbissonYaoundeCameroon

Mount Cameroon volcano has erupted several times in the 20 th Century with documented eruptions in 1909,1922,1954,1959,1982,1999 and *** of historic volcanism is represented by several older lava flows and lahar deposits around the flanks of the *** study aims to assess the evolution of Mount Cameroon volcanism through its eruptive history via interpretation of mineralogical,whole rock geochemical and Pb,Sr,Nd isotope data generated from historic and recent lava *** this study,samples were collected from the 1959,1982,1999 and 2000 eruptions and from several historic eruption sites with unknown eruption *** of major and trace element data demonstrates that Mount Cameroon is geotectonically associated with within-plate Ocean Island Basalt *** than 90%of the studied historic lavas(n=29)classify as tephrites and basanites whereas the modern lavas(n=38)are predominantly trachybasalts,demonstrating evolution from primitive to evolved lavas over time typically in response to fractional ***,the lavas are porphyritic with main mineral phases being olivine,clinopyroxene,plagioclase feldspars and Fe-Ti-Cr *** 1982 lavas are predominantly aphyric and dominated by lath-shaped flow-aligned plagioclase in the *** chemistry shows variable forsterite compositions from *** vary from diopside through augite to titanaugite with chemical composition ranges from Wo45En32Fs7 to *** feldspars vary from labradorite(An567 O)to bytownite(An80-87).For the Fe-Ti-Cr oxides,calculated ulvospinel component shows a wide variation from ***-normative classification on the Di-Ol-Hy-Qz-Ne system shows that all Mount Cameroon lavas are nepheline-normative(Ne ranges from4.20 wt.%to 11.45 wt.%).radiogenic isotope data demonstrate that Mount Cameroon lavas are HIMU(or high μ=238U/204Pb),characterized by 206Pb/204Pb=20.19-20.46,207Pb/204Pb=15.63-15.69,208Pb/204

关键词： Mount Cameroon HIMU Petrogenesis Geochemical evolution radiogenic isotopes Mineral chemistry

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Geochemistry of Enclaves and Host Granitoids from the Kashan Granitoid Complex, Central Iran: Implications for Enclave Generation by Interaction of Cogenetic Magmas

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Journal of Earth Science 2015年第5期26卷 626-647页

作者： Maryam Honarmand Nematollah Rashidnejad Omran Franz Neubauer Ghasem Nabatian Mohammad Hashem Emami Albrecht von Quadt Yunpeng Dong Manfred Bernroider Department of Earth Sciences Institute for Advanced Studies in Basic Sciences (IASBS) Department of Geology Faculty of Basic Sciences Tarbiat Modares University Department Geography and Geology University of Salzburg Department of Geology Faculty of Sciences University of Zanjan Research Institute for Earth Sciences Geological Survey of Iran Institute of Isotope Geology and Mineral Resources ETH Zürich State Laboratory of Continental Dynamics Department of Geology Northwest University

The major and trace elements and Sr-Nd-Pb isotopes of Miocene host granitoid rocks and their mafic microgranular enclaves（MMEs） were studied to understand the petrogenesis of MMEs in the Kashan complex, which is part of the Urumieh-Dokhtar magmatic belt（Iran）. The host rocks consist of quartz-diorite and tonalite associated with a dioritic intrusion. The enclaves show microgranular texture and the same mineralogy as their respective host with plagioclase, quartz and biotite. MMEs have a diorite to quartz-diorite composition and show geochemical characteristics mostly between their granitoid host and the diorite intrusion. Chondrite-normalized REE patterns of all samples are moderately fractionated [（La/Yb）N=2.1 to 12.9]. The MMEs display in part small negative Eu anomalies（Eu/Eu＊=0.54 to 0.99）, with enrichment of LILE and depletion of HFSE. The enclaves show emplacement depth of -4 to 6 km which is comparable with the host rocks. Moreover, the Hornblende-plagioclase equilibrium temprature of MMEs yields average temperatures of 795℃ which is slightly higher than the host ones. Identical mineral compositions and Nd-Sr-Pb isotopic features of MME-host granitoid pairs indicate interactions and parallel evolution of MME and enclosing granitoid in the Kashan plutons. Additionally, the geochemical and isotopic investigations of host and dioritic intrusions suggest a common source for their genesis. A thermal anomaly induced by underplated basic magma into a hot crust would have caused partial melting in the lower crust to generate Kashan granitoid rocks.

关键词： magma interaction mafic microgranular enclave radiogenic isotopes granitoid rocks Kashan Urumieh-Dokhtar magmatic belt

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Geology and geochemistry of the Early Carboniferous Eastern Sawur caldera complex and associated gold epithermal mineralization,Sawur Mountains,Xinjiang,China

Geology and geochemistry of the Early Carboniferous Eastern ...

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中国科学院地质与地球物理研究所2008学术年会

作者： Ping Shen~*,Yuanchao Shen,Tiebing Liu,Guangming Li,Qingdong Zeng Key Laboratory of Mineral Resources,Institute of Geology & Geophysics,Chinese Academy of Sciences,P.O.Box 9825, Beijing 100029,People’s Republic of China

Volcanic rocks associated with Early Carboniferous gold mineralization are well exposed in the eastern part of Sawur Mountains, Xinjiang,*** results for these volcanic rocks recognize the Eastern Sawur caldera complex and broadly subdivide the volcanic -magmatic activity into the three cycles and nine *** Eastern Sawur caldera complex consists of at least one elliptical andesite caldera,associated with later and smaller circular andesite caldera,mafic volcanic necks and mafic to felsic dikes. The effusive rocks have a transitional character from calc-alkaline to tholeiite,range from porphyritic basalts,basaltic andesites,andesites to dacites,are enriched in large ion lithophile elements(LILE) and depleted in high-field strength elements(HFSE) relative to NMORB, with a pronounced negative Nb ***-normalized rare earth element(REE) patterns show enrichment in the light REE relative to heavy *** volcanic rocks have near-uniform initial Sr/Sr(0.70335-0.70362) and sup>143Nd/Nd(0.51254- 0.51259;ε = 3.5-4.7) *** rocks originated from the partial melting of a subduction-modified mantle wedge in a subduction *** wedge represents an enriched MORB mantle source with some transfer of subduction components to the wedge during the magmas *** assimilation could have played a role in petrogenesis during the ascent of the *** characteristics of these volcanic rocks are consistent with their formation in a subduction-related tectonic setting during the Early Carboniferous. A close spatial and temporal relationship exists between the volcanic rocks and hydrothermal gold mineralization in the Sawur Mountains. Intermediate to silicic volcanic rocks and/or caldera fracture system host a number of gold *** is evidence for a direct genetic association,*** two processes are linked by the common mantle-derived *** studies have suggested that oreforming fluids mainly derived from mantl

关键词： Eastern Sawur caldera complex Volcanism Geochemistry radiogenic isotopes Gold mineralization Sawur Mountains

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