scholarly journals Mesoproterozoic diamondiferous ultramafic pipes at Majhgawan and Hinota, Panna area, central India: Key to the nature of sub-continental lithospheric mantle beneath the Vindhyan basin

2006 ◽  
Vol 115 (1) ◽  
pp. 161-183 ◽  
Author(s):  
N. V. Chalapathi Rao
Keyword(s):  
Lithospheric Mantle ◽  
Central India ◽  
Vindhyan Basin ◽  
Continental Lithospheric Mantle

Lateral flow of thick continental lithospheric mantle during tectonic quiescence

2021 ◽  
Vol 145 ◽  
pp. 101830
Author(s):  
Claudio Alejandro Salazar-Mora ◽  
Victor Sacek
Keyword(s):  
Lithospheric Mantle ◽  
Lateral Flow ◽  
Continental Lithospheric Mantle

Lherzolite - carbonatite melt interaction in the presence of additive CO2 and H2O: Experimental data at 5.5 GPa and 1200-1450°C

2021 ◽  
Author(s):  
Aleksei Kruk ◽  
Alexander Sokol
Keyword(s):  
Experimental Data ◽  
Lithospheric Mantle ◽  
Fluid Phase ◽  
Experimental Results ◽  
Silicate Melt ◽  
Silicate Melts ◽  
Garnet Lherzolite ◽  
Russian Science ◽  
Continental Lithospheric Mantle

<p>We study the reaction of garnet lherzolite with carbonatitic melt rich in molecular CO<sub>2</sub> and/or H<sub>2</sub>O in experiments at 5.5 GPa and 1200-1450°C. The experimental results show that carbonation of olivine with formation of orthopyroxene and magnesite can buffer the CO<sub>2</sub> contents in the melt, which impedes immediate separation of CO<sub>2</sub> fluid from melt equilibrated with the peridotite source. The solubility of molecular CO<sub>2</sub> in melt decreases from 20-25 wt.% at 4.5-6.8 wt.% SiO<sub>2</sub> typical of carbonatite to 7-12 wt.% in more silicic kimberlite-like melts with 26-32 wt.% SiO<sub>2</sub>. Interaction of garnet lherzolite with carbonatitic melt (2:1) in the presence of 2-3 wt.% H<sub>2</sub>O and 9-13 wt.% molecular CO<sub>2</sub> at 1200-1450°С yields low SiO<sub>2</sub> (<10 wt.%) alkali‐carbonatite melts, which shows multiphase saturation with magnesite-bearing garnet harzburgite. Thus, carbonatitic melts rich in volatiles can originate in a harzburgite source at moderate temperatures common to continental lithospheric mantle (CLM).</p><p>Having separated from the source, carbonatitic magma enriched in molecular CO<sub>2</sub> and H<sub>2</sub>O can rapidly acquire a kimberlitic composition with >25 wt.% SiO<sub>2 </sub>by dissolution and carbonation of entrapped peridotite. Furthermore, interaction of garnet lherzolite with carbonatitic melt rich in K, CO<sub>2</sub>, and H<sub>2</sub>O at 1350°С produces immiscible kimberlite-like carbonate-silicate and K-rich silicate melts. Quenched silicate melt develops lamelli of foam-like vesicular glass. Differentiation of immiscible melts early during ascent may equalize the compositions of kimberlite magmas generated in different CLM sources. The fluid phase can release explosively from ascending magma at lower pressures as a result of SiO<sub>2</sub> increase which reduces the solubility of CO<sub>2</sub> due to decarbonation reaction of magnesite and orthopyroxene.</p><p>The research was performed by a grant of the Russian Science Foundation (19-77-10023).</p>

scholarly journals Pyrite Textures, Trace Elements and Sulfur Isotope Chemistry of Bijaigarh Shales, Vindhyan Basin, India and Their Implications

Minerals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 588
Author(s):  
Indrani Mukherjee ◽  
Mihir Deb ◽  
Ross R. Large ◽  
Jacqueline Halpin ◽  
Sebastien Meffre ◽  
...  
Keyword(s):  
Trace Elements ◽  
Trace Element ◽  
Sulfur Isotope ◽  
Volcanic Rocks ◽  
Central India ◽  
High Energy ◽  
Vindhyan Basin ◽  
Mean Values ◽  
Fine Grained ◽  
Sedimentary Pyrite

The Vindhyan Basin in central India preserves a thick (~5 km) sequence of sedimentary and lesser volcanic rocks that provide a valuable archive of a part of the Proterozoic (~1800–900 Ma) in India. Here, we present an analysis of key sedimentary pyrite textures and their trace element and sulfur isotope compositions in the Bijaigarh Shale (1210 ± 52 Ma) in the Vindhyan Supergroup, using reflected light microscopy, LA-ICP-MS and SHRIMP-SI, respectively. A variety of sedimentary pyrite textures (fine-grained disseminated to aggregates, framboids, lags, and possibly microbial pyrite textures) are observed reflecting quiet and strongly anoxic water column conditions punctuated by occasional high-energy events (storm incursions). Key redox sensitive or sensitive to oxidative weathering trace elements (Co, Ni, Zn, Mo, Se) and ratios of (Se/Co, Mo/Co, Zn/Co) measured in sedimentary pyrites from the Bijaigarh Shale are used to infer atmospheric redox conditions during its deposition. Most trace elements are depleted relative to Proterozoic mean values. Sulfur isotope compositions of pyrite, measured using SHRIMP-SI, show an increase in δ34S as we move up stratigraphy with positive δ34S values ranging from 5.9‰ (lower) to 26.08‰ (upper). We propose limited sulphate supply caused the pyrites to incorporate the heavier isotope. Overall, we interpret these low trace element signatures and heavy sulfur isotope compositions to indicate relatively suppressed oxidative weathering on land during the deposition of the Bijaigarh Shale.

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