Journal
JOURNAL OF STRUCTURAL GEOLOGY
Volume 88, Issue -, Pages 63-72Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jsg.2016.05.003
Keywords
Mohr circle; Quartz veins; Gold mineralization; Fluid pressure; Gadag; India
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Funding
- Ministry of Earth Sciences (MoES, New Delhi) [MoES/P.O(Geosci)/1/2013]
- IIT Kharagpur
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In this study, orientations of 157 quartz veins occurring in metabasalts of the Gadag region (Dharwar craton, southern India) are used to plot the 3-D Mohr stress circle, which provides information about relative stress/fluid pressure (P-f) conditions, as well as stress state during P-f fluctuation. To scale the 3-D Mohr circle, vein orientation data are integrated with (a) available estimates from fluid inclusions of highest recorded P-f (390 MPa) and lowest recorded P-f (50 MPa) and (b) intrinsic rupture criterion that empirically quantify rock properties. Based on the scaled 3-D Mohr circle, the absolute magnitudes of the three principal stresses are quantified for high and low P-f. Of 157 veins investigated here, 14 veins are identified as having favourable orientation for dilation at high as well as low P-f. These 14 veins have a mean strike of 150 degrees, which is similar to the orientation of the gold-bearing quartz lodes reported in the region. The effective normal stress (sigma(')(n) = sigma(n)-P-f) prevalent during dilation of fracture/fabric anisotropy with 150 degrees strike is calculated to be -11.5 MPa at high P-f, and -1.0 MPa at low P-f. Thus, it is interpreted that in the Gadag region, a change in sigma(')(n) of 10.5 MPa prevailed during P-f fluctuation and associated separation of gold from the fluid. (C) 2016 Published by Elsevier Ltd.
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