First Report of Florencite from the Singhbhum Shear Zone of the East Indian Craton. (3rd February 2014)

• Record Type: Journal Article
• Authors: Chakraborty, Maitrayee; Biswas, Sayan; Sengupta, Nandini; Sengupta, Pulak
• Other Names: Arima M. Academic Editor.; Belluso E. Academic Editor.; Jordán Vidal M. M. Academic Editor.; Warr L. N. Academic Editor.
• Is Part Of: International journal of mineralogy. Volume 2014(2014)
• Publication Date: 2014-02-03
• Subjects: Mineralogy -- Periodicals; Mineralogy; Electronic journals; Periodicals; 549.05
• DOI: 10.1155/2014/978793
• Languages: English
• ISSNs: 2356-7058

Abstract

Abstract : Metamorphic florencite is being reported from kyanite-rich rocks from the eastern part of the Palaeo- to Mesoproterozoic Singhbhum shear zone. This is the first report of florencite from the Precambrian rocks of the Indian Shield. Host rock of florencite is a kyanite-rich rock (>80 vol%) with small and variable amounts of quartz, lazulite, augelite, and rutile. Florencite forms small (<20 microns) idioblastic-to-subhedral crystals that are included in large kyanite grains. Rarely, florencite replaces kyanite. The florencite has small proportion of crandallite (8.7–11.8 mol%) and goyazite (<2 mol%) components. Florencite of this study is dominated by Ce (~49 mol%) with significant La (~30 mol%) and Nd (~21 mol%). Compared to other florencite occurrences of the world, florencite of the studied rock is impoverished in S, Sr, and Ba and rich in P. Stability of the assemblage florencite-kyanite-augelite-lazulite and the quantitative thermobarometry in the adjoining rocks suggest that florencite was formed during Palaeoproterozoic metamorphism that culminated at theP - T range of490 ± 40 ∘ C and6.3 ± 1 kbar. Integrating all the geological features it is postulated that florencite was formed due to metasomatism of some aluminous protolith by infiltration of acidic fluids charged withPO 4 - 3 and LREE.