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Bhargava, M.
- Cu-Mo-Au Metallogeny Associated with Proterozoic Tectono-Magmatism in Malanjkhand Porphyry Copper District, Madhya Pradesh
Authors
1 Hindustan Copper Ltd., Malanjkhand - 481 116, Madhya Pradesh, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 56, No 4 (2000), Pagination: 395-413Abstract
Regional studies covering the Malanjkhand granitoid pluton have indicated various features related to Cu-Mo-Au metallogeny in the area. The rocks belong to Archaem and Proterozoic sequences and are similar to those occurring further south of Malanjkhand in the Dongargarh area.
Malanjkhand pluton is emplaced in an environment favourable for Cu-Mo-Au mineralization. It is located at the northern end of the Kotri-Dongargarh mobile belt. Magmatic differentiation resulting in a copper-bearing hydrothermal phase could be the source of copper. The mineralized vein systems occur close to microgranitoid intrusions, which are the most differentiated rocks in the area. Hydrothermal activity could be related to these intrusives.
Regional structures indicate a marked similarity in orientation of megascopic fabric elements such as shears and fractures, schistosity and gneissosity, faults, orientation of quartz veins and dykes. All the elements indicate a dominant N-S trend and the role of regional stresses. The fissures and mylonitized shear zones provided the channels through which acidic and basic magmatic activity took place.
The ore mineral assemblages include Cu-Mo-Au with Ag and traces of Co. The veins are emplaced in shear zones in the granitoids, along schistosity planes in older schistose and gneissic rocks and at the contact of granitoids with Nandgaon volcanics. Most veins, basic dykes and microgranitoid intrusions occur in a 10 km wide zone of intense tectonic and magmatic activity.
Hydrothermal alteration has affected the Malanjkhand gmitoid. Alteration is stronger close to the mineralized veins. The alteration assemblages identified are potassic and propylitic. Potash metasomatism has produced K-rich zones close to mineralization. Pink granitoids contain higher amount of Fe2O3 compared to the gray granitoids. This is due to the presence of hematite introduced during potassic alteration. Alteration sequences and genetic models have been proposed, which can be used as guidelines for further exploration in the province.
Mineralization associated with the granitoids at Malanjkhand and elsewhere in the region is of porphyry type. Various characteristics such as tectonic regime, association of I-type calc-alkaline granitoids, hydrothermal alteration, stockwork of mineralized veins, strong structural control, temperature of formation, huge tonnage and low tenor are features akin to various porphyry deposits of the world, especially those associated with plutonic rocks.
