Timing of Gold Mineralization in the Hutti Gold Deposit, Dharwar Craton, South India

Abstract

The Hutti orogenic gold deposit, in the eastern Dharwar craton of South India, is located in a cuspate greenstone belt which is tectonically juxtaposed against tonalite-trondhjemite-granodiorite (TTG) basement on its western margin. The host rocks to gold mineralization are mafic and felsic volcanic rocks metamorphosed to the amphibolite facies. Mineralization is confined to nine, broadly parallel, quartz reefs within north-south-to north-northwest-south-southeast-trending shear zones that dip approximately 70°W. Six of these 2-to 10-mthick, boudinaged veins have been mined to a depth of over 810 m. Free gold occurs in the veins and alteration haloes and is spatially and temporally associated with quartz and disseminated pyrite and arsenopyrite which, in turn, are closely associated with hydrothermal monazite and xenotime in the biotite-plagioclase wallrock alteration around veins. Gold is considered to have been deposited during D2 to D3 deformation, broadly coincident with the emplacement of syntectonic granitoids.The history of volcanism, granitic magmatism, and gold mineralization is defined by U-Pb geochronology of magmatic zircons and hydrothermal monazite and xenotime. The felsic volcanic host rocks have a U-Pb zircon age of 2587 ± 7 Ma, about 40 m.y. older than the age of gold mineralization at 2547 ± 10 Ma determined from hydrothermal monazite. The syntectonic Kavital granitoid has a U-Pb zircon age of 2545 ± 7 Ma, which overlaps with the timing of gold deposition and is consistent with structural interpretations. The Ramagiri and Kolar gold deposits elsewhere in the Dharwar craton are considered to have a similar structural timing, and the Hutti geochronology suggests that gold mineralization occurred throughout the Dharwar craton some 80 to 120 m.y. later than the major peak of Late Archean world-class orogenic gold mineralization in most other Archean

Eastern Dharwar Craton, India: Continental lithosphere growth by accretion of diverse plume and arc terranes

“…Felsic volcanic rocks of the Buddine Formation have been dated by U-Pb method at 2586 AE 50 Ma (Rogers et al, 2007), and granodioritic clasts present in the conglomerate yielded a SHRIMP zircon ages of 2576 AE 12 Ma . Recent studies have documented that the U-Pb zircon age of the felsic volcanic rocks of Hutti belt are 2587 AE 7 Ma and the age of gold mineralization is 2547 AE 10 Ma (Sarma et al, 2008;Ram Mohan and Sarma, 2010). The available geochronological data indicate that this belt was formed w2.6 Ga.…”

In situ U-Pb dating of xenotime by laser ablation (LA)-ICP-MS

“…This mineral is enriched in rare earth elements (REE), and is an ideal candidate for U-Pb dating because of its high content of U and negligible content of common Pb. Currently, in situ dating of xenotime is commonly conducted by ion microprobe [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20], which can yield precise and accurate ages. However, the expense of this instrumentation hinders the wide application of this technique.…”

Pb, Sr and Nd isotope systematics of metavolcanic rocks of the Hutti greenstone belt, Eastern Dharwar craton: Constraints on age, duration of volcanism and evolution of mantle sources during Late Archean

“…Giritharan and Rajamani, 1998;Pal and Mishra, 2002;Pandalai et al, 2003;Rogers et al, 2007;Srinivasa Sarma et al, 2008;Manikyamba et al, 2009). This paper presents the findings of Rb-Sr, Sm-Nd and Pb-Pb isotope study on the metavolcanic rocks of the Hutti greenstone belt and integrates with the results of the earlier geochronological studies to decipher the age and duration of formation of volcanic rocks of the belt and to better understand crust-mantle evolution in the eastern Dharwar craton.…”

“…Rogers et al (2003Rogers et al ( , 2007 have reported SHRIMP ages of 2523 ± 44 Ma (MSWD = 3.6) and 2586 ± 59 Ma (MSWD = 0.82) for zircons separated from felsic volcanic rocks found in the Hutti gold mine and they have suggested that these are minimum magmatic ages. Srinivasa Sarma et al (2008) have reported a SHRIMP U-Pb Concordia age of 2587 ± 7 Ma (MSWD = 1.3) for zircons recovered from a meta-rhyolite sample from the Hutti gold mine which they considered as the age of magmatic zircon growth. However, time of formation of the metabasalts the predominant rock type in the Hutti greenstone belt is not yet reported.…”