Geochemical and SmNd isotopic study of Neoproterozoic ophiolites from southeastern China: petrogenesis and tectonic implications

Li, Xian‐Hua; Zhao, Jun‐Hong; McCulloch, Malcolm T.; Zhou, Guoqing; Fengming, Xing

doi:10.1016/s0301-9268(96)00032-0

Cited by 136 publications

(69 citation statements)

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“…The Cathaysia block is composed predominantly of a Neoproterozoic-early Paleozoic assemblage of variably metamorphosed sedimentary and igneous rocks along with minor Paleoproterozoic igneous rocks (Shu 2012). In the early to middle Neoproterozoic, the Cathaysia and Yangtze blocks were accreted along the Jiangnan orogenic belt to form the unified South China Craton (Shu 2012;Cawood et al 2013;Wang et al 2013), with exposures of Neoproterozoic ophiolite in the east Jiangnan belt (Shu et al 1994;Li et al 1997;Shu 2012) and along the northwestern margin of the Yangtze block (Sun and Vuagnat 1992).…”

Section: Geological Setting and Sample Descriptionsmentioning

confidence: 99%

An Early Neoproterozoic Accretionary Prism Ophiolitic Mélange from the Western Jiangnan Orogenic Belt, South China

Yao

Cawood

Shu

et al. 2016

The Journal of Geology

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A B S T R A C TThe Neoproterozoic Jiangnan orogenic belt delineates the suture zone between the Cathaysia and Yangtze blocks of the South China Craton. The western part of the belt, in the Longsheng region, consists of a disrupted mafic-ultramafic assemblage of pillow basalt, gabbro, diabase, and peridotite along with siliceous marble, ophicalcite, and jasper mixed with basalt. Significant talc deposits occur on the margins of the ultramafic bodies as well as in the transition zone between marble and basalt. Primary rock relations are largely overprinted by pervasive shearing, resulting in disruption of the assemblage into series of discontinuous blocks within a phyllite matrix. West-dipping thrust faults mark the eastern contact of blocks, and the overall succession has the appearance of a tectonic mélange. U-Pb zircon age data from the gabbros and diabases yield crystallization ages of 867 5 10, 863 5 8, and 869 5 9 Ma, with positive εHf(t) values. The gabbro, basalt, serpentinite, and some talc samples display minor light rare earth element-enriched patterns with obvious depletion of Nb and Ta, indicating a subduction-related setting. The tuffaceous phyllite shows similar geochemical features. A few mafic rocks and the altered ultramafic rocks display mid-ocean ridge basalt (MORB) affinity. Overall lithostratigraphic relationships, age data, and geochemical signatures suggest a forearc setting that was imbricated and disrupted within an accretionary prism environment to form an ophiolitic mélange. The pillow basalt, red jasper, and MORB-type mafic-ultramafic rocks within the mélange occur as exotic blocks derived from the subducting oceanic plate, whereas the arc-type mafic rocks occur as autochthonous blocks, which are all exposed in a matrix of sandy and tuffaceous phyllite.

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Section: Geological Setting and Sample Descriptionsmentioning

confidence: 99%

An Early Neoproterozoic Accretionary Prism Ophiolitic Mélange from the Western Jiangnan Orogenic Belt, South China

Yao

Cawood

Shu

et al. 2016

The Journal of Geology

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“…Mean carbon isotope compositions for whole Hunan diamonds range from 22.2‰ to 2.5‰ [25]. These observations are consistent with early to late Proterozoic subduction and collision-subduction events within the Yangtze Craton, which may have transported carbon with a crustal isotopic signature into the lithospheric mantle beneath the Yangtze Craton [44][45][46][47]. This implies a fundamental difference (e.g.…”

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confidence: 68%

Variations in carbon isotopic composition in the subcontinental lithospheric mantle beneath the Yangtze and North China Cratons: Evidence from in-situ analysis of diamonds using SIMS

Chen¹,

Zhili

Lu³

et al. 2012

Chin. Sci. Bull.

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The components and evolution of subcontinental lithospheric mantle beneath the North China Craton and the Yangtze Craton is a current topic in the geological study of China and the carbon isotopic composition of diamond is one of the most direct probes into cratonic lithospheric mantle processes. In this paper, in-situ SIMS (Secondary Ion Mass Spectrometry) techniques were used to analyze the carbon isotope compositions at different internal growth zones of diamonds from Shandong and Liaoning in the North China Craton and Hunan in the Yangtze Craton. It was found that the carbon isotopic range of diamonds from the North China Craton are rather distinct from those of the Yangtze Craton; the former has a range of 6.0‰ to 2.0‰ (relative to VPDB) with an average value of 3.0‰ in their core areas, which is consistent with global peridotitic diamonds; the diamonds from the Yangtze Craton, however, have a carbon isotopic range from 8.6‰ to 3.0‰ with an average value of 7.4‰ in their core areas, being more consistent with global eclogitic diamonds. The variations of carbon isotope ratios between different internal growth zones in individual diamonds were different in the three diamond localities studied. There was a clear correlation between changes in carbon isotopic composition and phases of diamond dissolution and new growth, while no correlation was observed between   13 C and internal inclusions. The variations suggest that the carbon isotopic compositions of mantle fluids were changing during the process of diamond crystallization, and that the heterogeneity of the carbon isotopic composition in mantle carbon reservoirs was a more important factor than carbon isotope fractionation in controlling the carbon isotopic compositions and their variation in diamonds. In addition, the preliminary results of in-situ nitrogen analyses demonstrated that the variation of carbon isotopic compositions between the core and outer growth zones does not correlate with nitrogen abundances, implying either that diamonds crystallized in an open environment or that the carbon isotopic composition and nitrogen contents in mantle fluids were controlled by other, not yet understood factors. The experimental results provide hints that the isotopic composition of carbon and its original sources were different in metasomatic fluids controlling diamond formation in the mantle beneath the North China Craton and the Yangtze Craton.

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“…The tectonic evolu tion of SE China has been drawn attention since Hsu and his coworkers (e.g., Hsu et al, 1987Hsu et al, , 1988Hsu et al, , 1990 proposed a Mesozoic collision model for the Yangtze-Huanan tectonic evolution, which was drastically different from the traditional view of the Proterozoic collision between the two blocks. Many geological, geochemical and geo chronological studies on ophiolites, volcanic rocks, granitoids and sediments have been made to evaluate the tectonic evolution of SE China during last five years, which led a conclusion not to be accordant with the model by Hsu et al (Chen et al, 1991;Xing et al, 1992;Zhou, X. M. and Zhu, 1993;Li, X. H. et al, 1994Li, X. H. et al, , 1997Li, X. H. and McCulloch, 1996). The Proterozoic collision be tween the Yangtze and Huanan Blocks has now been well defined.…”

Section: Introductionmentioning

confidence: 99%

“…Three ophiolite suites which crop out in northern Guangxi, southern Anhui and northeast Jiangxi, respectively, were tectonically emplaced into the Banxi Group (and equivalent strata). Pet rological, geochemical and chronological studies are mainly focused on the Southern Anhui Ophiolites (SAHO) and Northeastern Jiangxi Ophiolites (NEJXO) to the southeastern margin of the Yangtze Block, and the origin and tectonic settings of them are still a matter of debate (Zhou, X. M. et al, 1989;Xu and Qiao, 1989; Zhou, G. and Zhao, 1991;Chen et al, 1991;Xing et al, 1992;Li, X. H. et al, 1994Li, X. H. et al, , 1997Zou et al, 1995). On the other hand, systematic geochemical and isotopic studies of the Longsheng Ophiolite (LSO) from northern Guangxi have, not been per formed.…”

Section: Introductionmentioning

confidence: 99%

“…In the south ern Anhui and northeastern Jiangxi Provinces, southeastern margin of the Yangtze Block, two ophiolite suites, i.e., the SAHO and NEJXO, were also tectonically emplaced into the Banxi low grade metamorphic rocks. The SAHO with well preserved original lithostratigraphic sequence consists of metamorphosed harzburgite, cumulate gabbro, spilite and keratophyre (Chen et al, 1991;Li, X. H. et al, 1997). The NEJXO is tectonically dismembered, and composed of serpentinized peridotite, cumulate gabbro, dolerite, diorite, anorthosite, plagioclase granite, spilite, keratophyre, basalt and andesite (Zhou, 1989).…”

Section: Introductionmentioning

confidence: 99%

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Geochemistry of the Longsheng Ophiolite from the southern margin of Yangtze Craton, SE China.

1997

Geochem. J.

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190

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Geochemical and Sm-Nd isotopic data are presented for basaltic volcanic rocks from the Longsheng Ophiolite, which were crystallized at 977 ± 10 Ma and tectonically emplaced into the Danzhou Group (Banxi equivalent) along the southern margin of the Yangtze Block, SE China during the Neoproterozoic. The volcanic rocks have undergone low-grade alteration and metamorphism, displaying high Na20 con tents (>5%) and a large variation of mobile elements, but a relatively small range of immobile elements. With enrichment of Th and LREEs, relatively low high-field-strength elements and other REEs, and the Ta-Nb-Ti negative anomaly, the volcanic rocks are geochemically similar to basalts forming in subduction related environments, typical of the "supra-subduction zone" ophiolites. Nd isotopes of the volcanic rocks preclude a MORB-like depleted mantle source for the Longsheng Ophiolite, though their Sm-Nd isotopic systems have been rehomogenized during the late Neoproterozoic alteration. The Longsheng volcanic rocks, therefore, are interpreted to have been generated either by extension and thinning of a continental arc, or at a backarc side of continental arc during the early stage of the backarc spreading.

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Geochemical and SmNd isotopic study of Neoproterozoic ophiolites from southeastern China: petrogenesis and tectonic implications

Cited by 136 publications

References 20 publications

An Early Neoproterozoic Accretionary Prism Ophiolitic Mélange from the Western Jiangnan Orogenic Belt, South China

An Early Neoproterozoic Accretionary Prism Ophiolitic Mélange from the Western Jiangnan Orogenic Belt, South China

Variations in carbon isotopic composition in the subcontinental lithospheric mantle beneath the Yangtze and North China Cratons: Evidence from in-situ analysis of diamonds using SIMS

Geochemistry of the Longsheng Ophiolite from the southern margin of Yangtze Craton, SE China.

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