To unravel the geochemical heterogeneity and its origin in different terranes of North China,we conducted geochronological and geochemical analyses of the meta-mafic rocks from the Lüliang–Zhongtiao rift zone(Sh...To unravel the geochemical heterogeneity and its origin in different terranes of North China,we conducted geochronological and geochemical analyses of the meta-mafic rocks from the Lüliang–Zhongtiao rift zone(Shanxi Province).LA-ICP-MS zircon U–Pb dating yielded mostly End-Neoarchean to Proterozoic ages for the basement rocks(Sushui Complex:2516±26 Ma;Metamafic rocks:2494±31 Ma),Jiangxian Group(~2213 Ma),Zhongtiao Group(2077±29 Ma),Jiehekou Group(1998±23 Ma),and Lüliang Group(2152±52 Ma).Petrographic characteristics show that the meta-mafic rocks from the Neoarchean–Paleoproterozoic Zhongtiaoshan(Sushui Complex)have similar geochemical characteristics to the overlying Jiangxian and Zhongtiao Groups.The Paleoproterozoic Lüliang andYejishan Group meta-mafic rocks from Lüliangshan also have similar geochemical characteristics but are geochemically different from similar-age rocks from Zhongtiaoshan.This shows that the late-stage rocks have a geochemical inheritance from the early-stage rocks in the same region and that the geochemical heterogeneity of rocks from different areas was originated from the inherited heterogeneity of the magma source.展开更多
Meta-mafic rocks from the eastern Mayo Kebbi massif(Pala area,Chad)provide new insights into the geodynamic evolution of the Central African Orogenic Belt(CAOB).Petrographic and geochemical analyses reveal that the me...Meta-mafic rocks from the eastern Mayo Kebbi massif(Pala area,Chad)provide new insights into the geodynamic evolution of the Central African Orogenic Belt(CAOB).Petrographic and geochemical analyses reveal that the meta-mafic rocks consist of amphibolites and métagabbros,derived from a basalts protolith.These rocks exhibit calc-alkaline to tholeiitic affinities and are characterized by granoblastic and microlitic porphyritic textures.Enrichment in light rare earth elements(LREE),parallel REE patterns,and systematic variations in major and trace elements indicate that fractional crystallization was the dominant differentiation process.These rocks formed in a primitive arc magmatic setting,with source components including N-MORB-type and depleted mantle.Discrimination diagrams(e.g.,V/Ti vs.Zr,Th/Yb vs.Nb/Yb)indicate an intra-oceanic subduction influence,supported by negative anomalies in Nb-Ta,Zr-Hf and Ti.These findings support a tectonic model involving an active margin between a mid-ocean ridge and an intra-oceanic arc,reflecting the closure or subduction of an ancient oceanic domain.展开更多
基金supported by the Strategic Priority Research Program (B) of Chinese Academy of Sciences (Grant No.XDB18010105)the Talent start-up fund of Guiyang University(2019039510821)。
文摘To unravel the geochemical heterogeneity and its origin in different terranes of North China,we conducted geochronological and geochemical analyses of the meta-mafic rocks from the Lüliang–Zhongtiao rift zone(Shanxi Province).LA-ICP-MS zircon U–Pb dating yielded mostly End-Neoarchean to Proterozoic ages for the basement rocks(Sushui Complex:2516±26 Ma;Metamafic rocks:2494±31 Ma),Jiangxian Group(~2213 Ma),Zhongtiao Group(2077±29 Ma),Jiehekou Group(1998±23 Ma),and Lüliang Group(2152±52 Ma).Petrographic characteristics show that the meta-mafic rocks from the Neoarchean–Paleoproterozoic Zhongtiaoshan(Sushui Complex)have similar geochemical characteristics to the overlying Jiangxian and Zhongtiao Groups.The Paleoproterozoic Lüliang andYejishan Group meta-mafic rocks from Lüliangshan also have similar geochemical characteristics but are geochemically different from similar-age rocks from Zhongtiaoshan.This shows that the late-stage rocks have a geochemical inheritance from the early-stage rocks in the same region and that the geochemical heterogeneity of rocks from different areas was originated from the inherited heterogeneity of the magma source.
文摘Meta-mafic rocks from the eastern Mayo Kebbi massif(Pala area,Chad)provide new insights into the geodynamic evolution of the Central African Orogenic Belt(CAOB).Petrographic and geochemical analyses reveal that the meta-mafic rocks consist of amphibolites and métagabbros,derived from a basalts protolith.These rocks exhibit calc-alkaline to tholeiitic affinities and are characterized by granoblastic and microlitic porphyritic textures.Enrichment in light rare earth elements(LREE),parallel REE patterns,and systematic variations in major and trace elements indicate that fractional crystallization was the dominant differentiation process.These rocks formed in a primitive arc magmatic setting,with source components including N-MORB-type and depleted mantle.Discrimination diagrams(e.g.,V/Ti vs.Zr,Th/Yb vs.Nb/Yb)indicate an intra-oceanic subduction influence,supported by negative anomalies in Nb-Ta,Zr-Hf and Ti.These findings support a tectonic model involving an active margin between a mid-ocean ridge and an intra-oceanic arc,reflecting the closure or subduction of an ancient oceanic domain.
