TY  - JOUR
A1  - Mukherjee, Shreya
A1  - Adhikari, Avishek
A1  - Nicoli, Gautier
A1  - Vadlamani, Ravikant
T1  - Neoarchean (similar to 2.73-2.70 Ga) accretionary history of the eastern Dharwar Craton, India
BT  - Lu-Hf and Sm-Nd garnet geochronologic constraints from the Karimnagar granulite-facies supracrustal enclaves
JF  - Precambrian research
N2  - Cratonic mid-crustal plutons may contain supracrustal enclaves that preserve evidence of an earlier growth history. The Eastern Dharwar craton records Neoarchean two-stage accretionary sequential growth (2.70 and 2.55 Ga) and a chronology of their enclaves could refine orogenic models. To test whether the metamorphic history of their enclaves was related to any of these stages, phase equilibria modelling and combined Lu-Hf and Sm-Nd geochronology on garnet were conducted on metapsammite, now preserved as garnet-orthopyroxene-cordierite gneiss. Phase equilibria modelling indicates peak metamorphic conditions, similar to 850 degrees C and similar to 8.5 kbar (M1a), were followed by near isothermal decompression to 5-6 kbar (M1b) and isobaric cooling to similar to 800 degrees C (M1c). The thermobaric gradient related to peak metamorphic conditions, similar to 30 degrees C kbar(-1), is typical of collisional orogens. Regression of the whole-rock and garnet, for sample S17b, yield Lu-Hf isochron ages of 2733 +/- 29 Ma, and for sample S18, 2724 +/- 13 Ma. A Lu-Hf weighted mean age for the porphyroblastic garnet suggests growth at 2725.5 +/- 11.9 Ma during the M1a-M1b stages. In contrast, the whole-rock sample S17b and the garnet fractions yield a Sm-Nd isochron age of 2696 +/- 10 Ma. From sample S18 the whole rock, garnet fractions, and orthopyroxene yield an isochron age of 2683 +/- 15 Ma. The garnet Sm-Nd weighted mean age at 2692.0 +/- 8.3 Ma constrains the M1b-M1c stages. We suggest that the protoliths to these supracrustal enclaves were deposited in an arc tectonic setting and underwent thickening followed by heating during peeled-back lithospheric convergence. Therefore, the earliest of the craton-forming accretionary stages is preserved as the similar to 2.73 Ga granulite-facies enclaves, marginally older than the 2.70-2.65 Ga cratonic greenstone volcanism. Tectonic exhumation of these mid-crustal granulite enclaves was in response to the late-Proterozoic (similar to 1.7 Ga) Bhopalpatnam orogeny.
KW  - Eastern Dharwar craton
KW  - Granulite enclaves
KW  - Garnet-orthopyroxene-cordierite gneiss
KW  - Lu-Hf
KW  - Sm-Nd
KW  - Geochronology
Y1  - 2022
U6  - https://doi.org/10.1016/j.precamres.2022.106657
SN  - 0301-9268
VL  - 375
PB  - Elsevier
CY  - Amsterdam
ER  -