Eclogite xenoliths from Wajrakarur kimberlites, southern India |
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| Authors: | S C Patel S Ravi S S Thakur T K Rao K V Subbarao |
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| Institution: | (1) Department of Earth Sciences, Indian Institute of Technology, Mumbai, India;(2) Geological Survey of India, Southern Region, Hyderabad, India |
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| Abstract: | Summary Mineralogical characteristics of eclogite xenoliths from three kimberlite pipes (KL2, P2 and P10) of the Proterozoic Wajrakarur
kimberlite field of southern India have been studied. In a rare sample of enstatite eclogite from the KL2 pipe garnet contains
microscopic triangular arrays of needles or blebs of omphacite, enstatite and rutile consistent with an origin by exsolution
parallel to the isometric form {111}. Discrete omphacite grains in the sample contain exsolved needles or blebs of enstatite
and garnet. Kyanite eclogites are abundant in the KL2 pipe which occasionally show a secondary ring of pure celsian around
kyanite grains. Omphacite Na2O contents in the eclogites of the KL2 and P2 pipes are typically between 3 and 6 wt%, and garnet has widely variable composition
with end member ranges of Prp22-81Grs0-47Alm10-30Sps0-1Adr0-5Uv0-3. Eclogites of the P10 pipe comprise chromian omphacite
and garnet. Phase relations in the ACF projection exhibit systematic increase of the Ca-Tschermak’s component in omphacite
from enstatite eclogite through biminerallic eclogite to kyanite eclogite. Garnet-clinopyroxene Fe–Mg geothermometry yields
temperatures mostly in the range of 900–1100 °C. A formerly supersilicic nature of garnet in enstatite eclogite as inferred
from exsolution mineralogy indicates minimum peak pressure of 5 GPa. |
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