Cordierite-spinel granulite paragenesis in Highland Complex khondalites: pressure-temperature paths?

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Lars Crust915 rep

What mineral reaction rims and peak metamorphic P-T conditions characterize aluminum-rich khondalite gneisses exposed near Balangoda?

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Accepted Answer

Khondalites—metamorphosed Proterozoic pelitic sediments comprising quartz, garnet, sillimanite, graphite, and K-feldspar—preserve diagnostic reaction textures recording near-isothermal decompression within the Highland Complex. Corona structures of cordierite surrounding sillimanite and garnet indicate that rocks subjected to peak granulite facies pressures exceeding 8 kbar experienced rapid decompression down to 4-5 kbar at temperatures near 800°C during Gondwana collisional unroofing.

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Dr Bandula Crust1860 rep

Green spinel (pleonaste) occurs as minute inclusions inside cordierite rims, shielding iron-magnesium ratios from retrograde chemical re-equilibration.

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Lars Crust915 rep

Fluid inclusion analysis in quartz lenses reveals high concentrations of dense CO2 fluids trapped at peak metamorphic conditions.

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Elena Spectra910 rep

Geological hammer collection in declared archaeological reserves requires prior scientific sampling permits from the Geological Survey and Mines Bureau (GSMB).

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Max Rigging925 rep

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