Detailed Exploration for Epigenetic Gold Deposit: A Case History: Hira-Buddinni Gold Deposit. Hutti-Maski Schist Belt, India

摘要

The Hira-Buddinni gold deposit is situated about 22 Kms. east of world class Hutti Gold deposit on the eastern limb of the Hutti-cross fold (F2) and close to the axis of the eastern synform of the Hutti-Maski greenstone belt. The area had witnessed the ancient and modern mining activities. Preliminary exploration has revealed about 660 m strike length auriferous zone. Based on the encouraging results of preliminary exploration and considering its proximity to main Hutti Mine and Mill, where all the infrastructure facilities are available, M/s HGML took up detailed exploration by trenching, diamond drilling and exploratory mining. The main litho-units of the area are amphibolite and acid volcanic rocks. The gold mineralization is epigenetic due to shear control and is hosted by basic, contact of basic-acid volcanic zone and in the acid volcanic rocks. Auriferous mineralization is manifested by the well sheared and highly silicified metabasalt mixed with the sheared acid volcanic rock. The shear zone is traversed by quartz veins, cutting across the shear zone from north to south (Ladder veins). At places quartz veins are conformable with the shear zone. The main sulphides in the mineralized zone are represented by pyrite, pyrrhotite and chalcopyrite. In the sheared acid volcanic rocks plagioclase-feldsfar is noticed. The main wall rock alterations are feldspathisation, Chaloritisation, silicification, carbonitisation/ calcification, biotitisation and sericitisation. At places highly brecciated, well sheared and quartz-sulphide rich zones are encountered. Mineralization is in the ductile, brittle-ductile and brittle shear zone. This auriferous shear zone trend varies from N 55° E to N 80° E with steep dip due north. At places dip is vertical to subvertical and also dip due south is also noticed. Lineation studies in subsurface development in general indicate a westerly pitch of the ore shoots. Structural features like shears, joints, faults and folds played a prominent role in localizing the auriferous vein and formation of the ore shoots. The theme of this paper is to trace the geology, gold mineralization, hydrothermal alteration, controls and guide to mineralization and exploration.