Different Origins of the Fractionation of Platinum-Group Elements in Raobazhai and Bixiling Mafic-Ultramafic Rocks from the Dabie Orogen, Central China

Liu, Qing; Hou, Quanlin; Xie, Lie‐Wen; Li, Hui; Ni, Shanqin; Wu, Yingliang

doi:10.1155/2012/631426

Cited by 4 publications

(1 citation statement)

References 46 publications

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“…Orogenic residual dunites (white diamonds with gray frame) refer to the complete dataset of orogenic dunites formed by high degrees of partial melting of mantle peridotites (collected by Su et al, 2016a). data sources for the Dabie-Sulu orogenic peridotites are as follows: Ganyu (Chen et al, 2006); Raobazhai (Zheng et al, 2008); Yangkou, Suoluoshu and Hujialing (Xie et al, 2013); Bixiling (Zheng et al, 2008;Liu Q et al, 2012). The whole-rock PGE data for the ancient mantle xenoliths from the North China Craton are from Gao et al (2002), Zheng et al (2005), Becker et al (2006), Zhang et al (2008), Liu et al (2010Liu et al ( , 2015.…”

Section: Discussionmentioning

confidence: 99%

Modification of an ancient subcontinental lithospheric mantle by continental subduction: Insight from the Maowu garnet peridotites in the Dabie UHP belt, eastern China

Chen

Chu

2017

Lithos

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Orogenic mantle-derived peridotites commonly originate from the subcontinental lithospheric mantle (SCLM) and thus provide a key target to investigate the modification of the SCLM by a subducting slab. The Maowu ultramafic rocks from the Dabie ultrahigh-pressure (UHP) metamorphic belt have formerly been debated as representing cumulates or mantle-derived peridotites. Detailed petrological and geochemical data presented in this study provide new constraints on the origin and formation of the peridotites involving melt depletion in the ancient SCLM and deep crustal metasomatism. The Maowu garnet dunites have refractory bulk compositions characterized by high Mg# (91.9-92.0) and Ni (2537-2892 ppm) values and low Al 2 O 3 (0.26-0.76 wt.%), CaO (0.05-0.32 wt.%), TiO 2 (<0.03 wt.%), Pd/Ir (0.40-0.46) and 187 Os/ 188 Os (minimum 0.11461) values. The Paleoproterozoic model ages (T RD = 2.1 Ga, T MA = 2.3 Ga) of the most refractory dunites represent minimum estimates for the age of the initial melt extraction. The extremely depleted nature, high olivine Fo (92.7-93.9), high Cr# (82-87) of spinel, and Re-Os isotopic data suggest that the Maowu garnet dunites are the residues of ~40% partial melting and represent a Paleoproterozoic fragment of the SCLM beneath the southeastern margin of the North China craton. Many garnet orthopyroxenite veins crosscutting the Maowu dunites preserve abundant metasomatic textures and show variable enrichment in incompatible elements. Mineral and whole-rock chemistry indicate that these veins represent metasomatic products between the wall dunites and silica-rich hydrous melts under UHP conditions. The veins show large variations in platinum-group element (PGE) signatures and Re-Os isotopes. The garnet-poor orthopyroxenite veins are characterized by low Al 2 O 3 (<2 wt.%) and S (<31 ppm) contents and have PGE patterns and 187 Os/ 188 Os ratios similar to the wall dunites, whereas the garnet-rich orthopyroxenite veins have high Al 2 O 3 (>6 wt.%) and S (99-306 ppm) contents and show melt-like PGE patterns and high 187 Os/ 188 Os ratios (up to 0.36910). These features, combined with the occurrence of interstitial sulfides in the garnet-rich orthopyroxenite veins, suggest that crust-derived sulfur-saturated silicate melts may have significantly modified the PGE signature and destroyed the Re-Os systematics the SCLM. However, when the crust-derived silicate melts became sulfur-depleted, such melts would not significantly modify the PGE patterns, radiogenic Os-isotope compositions or the Re-depletion model ages of the SCLM. Consequently, deep crust-mantle interactions in continental subduction zones could induce high degrees of Os isotopic heterogeneity in the SCLM wedge.

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Section: Discussionmentioning

confidence: 99%

Modification of an ancient subcontinental lithospheric mantle by continental subduction: Insight from the Maowu garnet peridotites in the Dabie UHP belt, eastern China

Chen

Chu

2017

Lithos

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Petrogenesis of Paleoproterozoic Khalari Hornblende‐Pyroxenite Intrusion Within the Dongargarh Supergroup, Bastar Craton: Insights From Petrological and Geochemical Studies

Samal,

Gautam,

Ashutosh

et al. 2024

Geological Journal

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This study investigates Paleoproterozoic hornblende pyroxenite, a lithological unit within the Khalari Ultramafic‐Mafic Complex (KUMC), which is intruded into the Neoarchean‐Paleoproterozoic Dongargarh Supergroup near Khalari village in the northern Bastar Craton. A comprehensive characterisation has been conducted through petrological analysis, bulk‐rock geochemistry, mineral chemistry, and platinum group elements (PGEs)‐Au geochemical studies to understand its petrogenesis and geotectonic implications. The presence of primary amphibole, specific pyroxene chemistry (low Ti and Cr), and enriched LILE, LREE and fluid‐mobile elements alongside negative Nb–Ta–Ti anomalies suggest these rocks were crystallised from a mantle melt originated from a metasomatized sub‐continental lithospheric mantle (SCLM) source. This metasomatization could be due to fluids derived from a subduction event predating the emplacement of the studied rocks. The proposed melt composition is estimated to have formed from 5% to 10% partial melting of a garnet‐rich peridotite mantle source. The crystallisation conditions are estimated to have occurred at an average pressure of 7.85 kbar and a temperature of 902°C, indicating moderately shallow depths influenced by fractional crystallisation and slow cooling rates. The emplacement of the KUMC is contemporaneous with several other magmatic activities in the Bastar Craton, around ca. 2.50–2.47 Ga, suggesting that mantle plume might have played a significant role in their formation. Low concentrations of PGEs in the studied samples indicate a PGE‐depleted mantle source.

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Destruction of the North China Craton triggered by the Triassic Yangtze continental subduction/collision: A review

Zhao

Zheng

Xiong

et al. 2018

Journal of Asian Earth Sciences

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Different Origins of the Fractionation of Platinum-Group Elements in Raobazhai and Bixiling Mafic-Ultramafic Rocks from the Dabie Orogen, Central China

Cited by 4 publications

References 46 publications

Modification of an ancient subcontinental lithospheric mantle by continental subduction: Insight from the Maowu garnet peridotites in the Dabie UHP belt, eastern China

Modification of an ancient subcontinental lithospheric mantle by continental subduction: Insight from the Maowu garnet peridotites in the Dabie UHP belt, eastern China

Petrogenesis of Paleoproterozoic Khalari Hornblende‐Pyroxenite Intrusion Within the Dongargarh Supergroup, Bastar Craton: Insights From Petrological and Geochemical Studies

Destruction of the North China Craton triggered by the Triassic Yangtze continental subduction/collision: A review

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