Open Access
Subscription Access
Open Access
Subscription Access
Granite-Molybdenite System of Ambalavayal, Kerala: Part I. Geochemistry and Petrogenesis of the Granite
Subscribe/Renew Journal
The 595 Ma old granite pluton punctures Precambrian low-alumina trondhjemites and occurs spatially related to the Moyar and Calicut fault-lineament. Mineralogically, it is a quartz-alkali-feldspar granite. Molybdenite occurs as disseminated flakes in the granite and associated pegmatites and as flaky aggregates in quartz veins. K: Na : Ca relationship suggests an adamellitic composition, whereas SiO2 vs. Log10K2O/MgO proportions confirm its alkaline nature. In Harker variation diagrams, the oxide weight percentages show overall magmatic trends. Among trace elements, the notable features are low large ion lithophile element contents, moderate to high transition element levels and extremely high light rare earth element values. High SiO2, K2O and Na2O values, with low abundance of Ba, Rb and Sr and enrichment of Nb and Zr are typical features comparable to alkali granites elsewhere. The Rb, Nb and Y characteristics denote a within-plate affinity. Petrochemical features indicate derivation of the granite from an alkali-enriched partial melt through quartz and alkali feldspar fractionation. The extremely high K/Rb values imply a K-enriched, Rb-depleted deep crustal source. The enrichment of LREE and HFS elements indicate an active role of CO2-rich volatiles in the petrogenetic regime.
Subscription
Login to verify subscription
User
Font Size
Information
Abstract Views: 207
PDF Views: 2