ePoster
Talk Description
This study reports phase relations and U–Th–Pbtotal in situ monazite geochronology of newly discovered mafic granulites from the Karimnagar Granulite Belt, Eastern Dharwar Craton, India. Orthopyroxene, garnet, Fe–Ti oxides, spinel and subordinate plagioclase constitute the mineralogy of studied samples. Detailed petrographic examination indicates two distinct mineralogical domains defined by garnet–orthopyroxene–plagioclase–quartz and hercynite–magnetite–ilmenite–corundum assemblages. The mineral assemblages suggest the following reaction:
1. Fe2TiO4 + O2 → (FeTiO3 +Fe2O3) ss +Fe3O4, FeAl2O4 + O2 → Fe3O4 +Al2O3
3. 3 Fe2SiO6 + 3 CaAl2Si2O8 → Ca3Al2Si3O12 + 2 Fe3Al2Si3O12 + 3 SiO2
Phase equilibria modeling of hercynite–magnetite–ilmenite–corundum assemblages indicates hematite–ilmenite–corundum stabilized from ulvospinel (as a lower lithosphere mantle lithology component) at a temperature of approximately 1000 and pressure of approximately 1.2 GPa. The phase diagrams also predict garnet stabilization at approximately 800 , 0.7 GPa by consuming plagioclase and orthopyroxene. The U–Th–Pbtotal in situ monazite dating indicates the presence of three distinct populations with weighted mean ages of 2586 ± 24 Ma, 2446 ± 12 Ma and 2091 ± 24 Ma respectively. The Neoarchean 2586 ± 24 Ma age is retrieved from a high-ThO2 monazite core. The slightly younger Plaeoproterozoic 2446 ± 12 Ma age is retrieved from relatively low-ThO2 rims that laced the high-ThO2 core. The youngest 2091 ± 24 Ma age is retrieved from irregular outer domains of monazite grains. When normalized with CI–Chondrite rare earth element contents, the Neoarchean monazite exhibit nearly flat to negative Eu anomaly. In contrast, the Early Paleoproterozoic monazites show flat to positive Eu anomaly.
Compared with the global tectonics, the Neoarchean 2586 ± 24 Ma ages are correlated with the accretion of the Eastern Dharwar Craton and Bastar Craton as a part of the extended Ur assembly (Santosh et al., 2004). The low-ThO2 monazite rims indicate intrusion and cooling of mafic dykes at 2446 ± 12 Ma. As mafic dyke intrusions are generally associated with rifting, we suggest the Eastern Dharwar Craton – Bastar Craton block rifted apart during c. 2446 Ma (Meshram et al., 2021)which marks the contact between the Bastar and Eastern Dharwar cratons in peninsular India. In this study, we attempt to constrain the petrogenesis of granulites from Gondpipri, Bhopalpatnam on the northern flank and Karimnagar on the southern flank of the Pranhita-Godavari valley using petrography, mineral and whole-rock geochemistry, fluid inclusion studies, and UPb zircon geochronology. The presence of relict magmatic textures and orthopyroxene chemistry is suggestive of an igneous protolith while CO2-rich fluid inclusions in quartz correspond to subsequent granulite-facies overprint. Geochemically, charnockites from both granulite belts are metaluminous, magnesian, and calc-alkaline, having similar Sr and Y concentrations, Rb/Sr, Sr/Y, LaN/SmN, GdN/YbN, and Eu/Eu* ratios, and positive BaPb and negative Nb-Ta-Ti anomalies. Zircons in charnockites from both granulite belts furnish magmatic crystallization ages of $\\sim$2.5 Ga (UPb isotope. The c. 2100 Ma ages from the monazite rims probably represent the thermal effect of a younger mafic dyke intrusion in the Dharwar and Bastar Craton (Satpathi et al., 2022).
Reference(s)
Tushar Meshram, M Lachhana Dora, Srinivasa R Baswani, Dewashish Upadhyay, Rajkumar Meshram, Kirtikumar Randive, Sameer Ranjan, and Jayanta K Nanda, 2021. Petrogenesis and UPb Geochronology of Charnockites Flanking the Pranhita Godavari Rift in Peninsular India-Link between the Bastar and Eastern Dharwar Cratons, Gondwana Research 92: p. 113–32.
M. Santosh, K Yokoyama, SK Acharyya, 2004. Geochronology and Tectonic Evolution of Karimnagar and Bhopalpatnam Granulite Belts, Central India, Gondwana Research, Volume 7, Issue 2, , p. 501-518, ISSN 1342-937X.
Kausik Satpathi, Hifzurrahman, Xie Hang-Qiang, AB Majeed Ganaie, Sagar Misra, Pritam Nasipuri 2022, A2-Type Granites from the Bastar Craton, South-Central India, and their Implication in Archean-Paleoproterozoic Tectonics in Indian Peninsula. Lithosphere 2022 (Special 8): 7938481.
1. Fe2TiO4 + O2 → (FeTiO3 +Fe2O3) ss +Fe3O4, FeAl2O4 + O2 → Fe3O4 +Al2O3
3. 3 Fe2SiO6 + 3 CaAl2Si2O8 → Ca3Al2Si3O12 + 2 Fe3Al2Si3O12 + 3 SiO2
Phase equilibria modeling of hercynite–magnetite–ilmenite–corundum assemblages indicates hematite–ilmenite–corundum stabilized from ulvospinel (as a lower lithosphere mantle lithology component) at a temperature of approximately 1000 and pressure of approximately 1.2 GPa. The phase diagrams also predict garnet stabilization at approximately 800 , 0.7 GPa by consuming plagioclase and orthopyroxene. The U–Th–Pbtotal in situ monazite dating indicates the presence of three distinct populations with weighted mean ages of 2586 ± 24 Ma, 2446 ± 12 Ma and 2091 ± 24 Ma respectively. The Neoarchean 2586 ± 24 Ma age is retrieved from a high-ThO2 monazite core. The slightly younger Plaeoproterozoic 2446 ± 12 Ma age is retrieved from relatively low-ThO2 rims that laced the high-ThO2 core. The youngest 2091 ± 24 Ma age is retrieved from irregular outer domains of monazite grains. When normalized with CI–Chondrite rare earth element contents, the Neoarchean monazite exhibit nearly flat to negative Eu anomaly. In contrast, the Early Paleoproterozoic monazites show flat to positive Eu anomaly.
Compared with the global tectonics, the Neoarchean 2586 ± 24 Ma ages are correlated with the accretion of the Eastern Dharwar Craton and Bastar Craton as a part of the extended Ur assembly (Santosh et al., 2004). The low-ThO2 monazite rims indicate intrusion and cooling of mafic dykes at 2446 ± 12 Ma. As mafic dyke intrusions are generally associated with rifting, we suggest the Eastern Dharwar Craton – Bastar Craton block rifted apart during c. 2446 Ma (Meshram et al., 2021)which marks the contact between the Bastar and Eastern Dharwar cratons in peninsular India. In this study, we attempt to constrain the petrogenesis of granulites from Gondpipri, Bhopalpatnam on the northern flank and Karimnagar on the southern flank of the Pranhita-Godavari valley using petrography, mineral and whole-rock geochemistry, fluid inclusion studies, and UPb zircon geochronology. The presence of relict magmatic textures and orthopyroxene chemistry is suggestive of an igneous protolith while CO2-rich fluid inclusions in quartz correspond to subsequent granulite-facies overprint. Geochemically, charnockites from both granulite belts are metaluminous, magnesian, and calc-alkaline, having similar Sr and Y concentrations, Rb/Sr, Sr/Y, LaN/SmN, GdN/YbN, and Eu/Eu* ratios, and positive BaPb and negative Nb-Ta-Ti anomalies. Zircons in charnockites from both granulite belts furnish magmatic crystallization ages of $\\sim$2.5 Ga (UPb isotope. The c. 2100 Ma ages from the monazite rims probably represent the thermal effect of a younger mafic dyke intrusion in the Dharwar and Bastar Craton (Satpathi et al., 2022).
Reference(s)
Tushar Meshram, M Lachhana Dora, Srinivasa R Baswani, Dewashish Upadhyay, Rajkumar Meshram, Kirtikumar Randive, Sameer Ranjan, and Jayanta K Nanda, 2021. Petrogenesis and UPb Geochronology of Charnockites Flanking the Pranhita Godavari Rift in Peninsular India-Link between the Bastar and Eastern Dharwar Cratons, Gondwana Research 92: p. 113–32.
M. Santosh, K Yokoyama, SK Acharyya, 2004. Geochronology and Tectonic Evolution of Karimnagar and Bhopalpatnam Granulite Belts, Central India, Gondwana Research, Volume 7, Issue 2, , p. 501-518, ISSN 1342-937X.
Kausik Satpathi, Hifzurrahman, Xie Hang-Qiang, AB Majeed Ganaie, Sagar Misra, Pritam Nasipuri 2022, A2-Type Granites from the Bastar Craton, South-Central India, and their Implication in Archean-Paleoproterozoic Tectonics in Indian Peninsula. Lithosphere 2022 (Special 8): 7938481.