Petrological and Geochemical Constraints in the Origin and Associated Mineralization of A-Type Granite Suite of the Dhiran Area, Northwestern Peninsular India

Abstract

Neoproterzoic, anorogenic, A-type granites of Dhiran area of Malani Igneous Suites is made up wholly of peralkaline-peraluminous alkali feldspar granites and is composed of K-feldspar, quartz, alkali amphibole, plagioclase, bio- tite and accessory minerals are iron oxides, monozite, zircon, apatite, and annite. This granitoid is associated with acid vol- canic and minor basic volcanic-plutonic and dykes. Petrographically, they show cloudy, patchy perthitic texture and graphic texture. They are highly evolved ferroan, alkaline, A-type granites, displaying the typical geochemical characteristics of A-type granites with high SiO2, Na2O + K2O, FeO*/MgO, Ga/Al, Zr, Nb, Ga, Y, Ce and rare earth elements (REE) and low CaO, MgO, Ba and Sr. Their trace and REE characteristics along with the use of various discrimination schemes revealed their correspondence to magmas derived from crustal origin. The extremely high Rb/Sr ratios combined with the obvious Sr, Ba, P, Ti and Eu depletions clearly indicate that these A-type granites were highly evolved and require advanced fractional crystallization in upper crustal conditions. These granites are high to medium content of radioactive element (U, Th, K) together Heat generation and Heat Production (HP). Leucocratic granites show higher Heat Production (4.84-8.75 µWm-3) and total Heat Generation Unit (11.52-20.84 HGU) than pink granite (2.09-2.94 µWm-3 (HP), 4.98-7.07 HGU). The gra- nites of the Dhiran area show higher average value of total Heat Generation Unit (16.51 HGU and 5.79 HGU) than the av- erage value of 3.8 HGU for the continental crust. The high Heat Generation Unit values (4.98-20.84) of the Dhiran granites indicate ‘hot crust’ category and a possible linear relationship between the surface heat flow and crustal heat generation in the Malani Igneous Suite.