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Charnockite granulite metamorphic petrogenesis: mapping Highland Complex orthopyroxene bands?

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L
Lucas Rock•915 rep

Where can structural field geologists inspect deep-crustal orthopyroxene-bearing charnockite type-sections across the Kadugannawa Complex road exposures?

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Sri Lanka’s Highland Complex is a classic global field locality for granulite-facies metamorphic petrology, characterized by enderbitic and charnockitic gneisses formed under extreme sub-crustal pressures (8-10 kbar) and temperatures (800-900°C) during Pan-African Gondwana assembly. Fresh diagnostic exposures containing greasy, dark greenish-grey hypersthene (orthopyroxene), bluish quartz, and perthitic microcline can be mapped in active road cuts along the A1 highway descending from Kadugannawa Pass toward Mawanella. The rocks show characteristic incipient charnockitization where carbonic fluids channeled along shear joints altered hornblende-biotite gneisses into dry pyroxene granulites in-situ.

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D
Dr Bandula Crust•1860 rep

Avoid sampling weathered surface rinds; atmospheric oxidation converts ferrous iron into brown ferric hydroxides, masking the diagnostic oily bottle-green color of fresh orthopyroxene crystals.

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L
Lucas Rock•915 rep

Thin sections viewed under cross-polarized light display characteristic pink-to-green hypersthene pleochroism alongside rounded almandine garnet blastesis.

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Elena Lumens•910 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 Rigging•925 rep

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