Geochemical constraints on the evolution of North China and Yangtze blocks

Benren, Zhang; Luo, Tao; Gao, Shan; Ouyang, Jianping; Han, Yingjie; Gao, Changlin

doi:10.1016/0743-9547(94)90052-3

Cited by 13 publications

(1 citation statement)

References 16 publications

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“…According to regional geological observations, and detailed chronological and petrological work, this granitoid belt is thought to be the product of "syncollision" (e.g. Zhang Benren et al, 1994;Sun Weidong et al, 2002).…”

Section: Introductionmentioning

confidence: 98%

Post-collisional plutonism with adakitic signatures: The Triassic Yangba granodiorite (Bikou terrane, northern Yangtze Block)

Qin

Lai

2008

Chin. J. Geochem.

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The post-collisional Yangba granodiorite intruded into the Bikou metasedimentary-volcanic group, southern Mianlue Suture, central China. The host granodiorites contain many mafic microgranular enclaves which have acicular apatite, phenocrysts of host granodiorites, implying that the enclaves have been incorporated as magma globules into host granodioritic magma and undergone rapid cooling. The variation trends of major and trace elements between enclaves and host rocks suggest a mixing and mingling process with respect to their petrogenesis. The mafic microgranular enclaves are characterized by shoshonite with SiO 2 63%, (4.54-6.18)>3.3, high K 2 O content (4.22%-6.04%), K 2 O/Na 2 O>1; in the K 2 O-SiO 2 diagram, all the samples plot in the shoshonite field, which are enriched in LILE and LREE, with obvious Nb, Ta negative anomalies, indicating a subducting fluid-metasomatised mantle source. Zircon LA-ICP-MS dating of the granodiorites yielded an age of 215.4±8.3 Ma, indicating they were formed during the late-orogenic or post-collisional stage ( 242±21 Ma) of the South Qinling Mountain Belt. The host granodiorites have many close compositional similarities to high-silica adakites from supra-subduction zone setting, but tend to have a higher concentration of K 2 O (3.22%-3.84%) and Mg # . Chondrite-normalized rare-earth element patterns are characterized by high ratios of (La/Yb) N , the extreme HREE depletion and a lack of significant Eu anomalies. In conjunction with the high abundances of Ba and Sr as well as the low abundances of Y and HREE, these patterns suggest a feldspar-poor, garnet ± amphibole-rich fractionation mineral assemblage. High Mg # values demonstrate that the host granodiorites were contaminated by enclave magma. On a whole, integrated geological and geochemical studies suggested the Yangba granodiorites and their mafic microgranular enclaves resulted from mixing of enriched mantle-derived shoshonitic magma and thickened lower crust-derived felsic magma. In combination with previous studies we consider that the Yangba granodiorites were likely to represent underplating activities and delamination of the lower crust during the late orogenic stage in western Qinling Orogenic Belt.

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Section: Introductionmentioning

confidence: 98%

Post-collisional plutonism with adakitic signatures: The Triassic Yangba granodiorite (Bikou terrane, northern Yangtze Block)

Qin

Lai

2008

Chin. J. Geochem.

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Heterogeneous sources of the Triassic granitoid plutons in the southern Qinling orogen: An E‐W tectonic division in central China

et al. 2013

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The Qinling orogen is an important orogenic belt formed by the collision between the North and South China blocks along the Mianlue suture during the Triassic. The orogen is customarily divided into the western and eastern Qinling terranes. However, the boundary has long been a matter of debate. There are many Triassic granitoid plutons in the orogen, especially in South Qinling, along the southern part of the Shangdan suture. Systematic analysis of U‐Pb ages and Hf isotopes in zircons frxom six granitoid plutons, including Guangtoushan, Gaoqiaopu, Xiba, Laocheng, Dongjiangkou, and Zhashui from west to east, allows us to trace their formation ages and source regions. All plutons yield ages that vary only from 218 to 211 Ma. However, zircon Hf‐isotope data for these Triassic plutons cluster in two distinct groups. Granitoids from the western segment (i.e., Guangtoushan, Gaoqiaopu, and Xiba) of the South Qinling belt have negative εHf(t) values (−20.9 to −5.2) and relatively old two‐stage Hf model ages (1.58 to 2.57 Ga). In contrast, those from the eastern segment (i.e., Laocheng, Dongjiangkou, and Zhashui) show higher εHf(t) values (−5.4 to +6.8) and younger two‐stage Hf model ages (0.82 to 1.60 Ga). Integrating these analyses with published Sr‐Nd‐Pb‐Hf isotopic data, we suggest that the division between the western and eastern South Qinling segments is located near the Taibai‐Chenggu line, between the Baoji‐Chengdu railway and 108°E longitude. The integrated data suggest that the western South Qinling segment separated from the North China block during the Paleoproterozoic and early Mesoproterozoic and then switched into continental convergence with the eastern South Qinling segment (northern margin of the Yangtze block) during the late Mesoproterozoic to early Neoproterozoic; finally, the two segments amalgamated during the late Neoproterozoic.

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Crustal evolution of the North Qinling terrain of the Qinling Orogen, China: Evidence from detrital zircon U–Pb ages and Hf isotopic composition

et al. 2011

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Geochemical constraints on the evolution of North China and Yangtze blocks

Cited by 13 publications

References 16 publications

Post-collisional plutonism with adakitic signatures: The Triassic Yangba granodiorite (Bikou terrane, northern Yangtze Block)

Post-collisional plutonism with adakitic signatures: The Triassic Yangba granodiorite (Bikou terrane, northern Yangtze Block)

Heterogeneous sources of the Triassic granitoid plutons in the southern Qinling orogen: An E‐W tectonic division in central China

Crustal evolution of the North Qinling terrain of the Qinling Orogen, China: Evidence from detrital zircon U–Pb ages and Hf isotopic composition

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