A New Occurrence of Sapphirine-Spinel-Corundum-bearing Granulite from NE of Jagtiyal, Eastern Dharwar Craton, Andhra Pradesh

Abstract

We report a new occurrence of sapphirine-spinel-corundum bearing granulites enclosed in granitic gneisses near Jagtiyal in the Eastern Dharwar Craton (EDC). These granulites are very important in deciphering the prehistory of the thermal peak of metamorphism due to the presence of refractory phases. The appearance of sapphirine is related to the following reactions: (a) Spl1 + Crd1 = Spr1 (2:2:1) (b) Phl (in Bt1) + Crn1 = East (in Bt2) + Spr2 (7:9:3) + Crd2 (c) Bt2 + Crd1 +Crn1 = Spr2 (7:9:3) + Kfs + H2O (d) Crd1 + Spl1 + Crn1 = Spr2 (7:9:3). The P–T evolution of these sapphirine granulites has been constrained through the use of THERMOCALC program. Temperature of formation of sapphirine-spinel assemblages is high, around 800 °C, and pressure ranges from 5-7 kbars, suggesting that sapphirine formation took place during decompression stage.

On ultrahigh temperature crustal metamorphism: Phase equilibria, trace element thermometry, bulk composition, heat sources, timescales and tectonic settings

“…However, the presence of sapphirine in a rock does not immediately indicate that the rockdand terranednecessarily records temperatures in excess of 900 C. For example, Kruckenberg and Whitney (2011) and Goergen and Whitney (2012b) reported symplectic sapphirine in quartzabsent MgeAl-rich rocks that attained temperatures of approximately 750 C. In addition, there are a number of occurrences of sap phirineespinelebiotite-bearing rocks (AE corundum AE ortho pyroxene AE plagioclase AE sillimanite AE garnet AE chlorite, and all quartz-absent) that appear to record temperatures less than 900 C (e.g. Oliver and Jones, 1965;Kelsey et al, 2005;Prakash and Sharma, 2008;Raith et al, 2008;Sharma and Prakash, 2008;Nasipuri et al, 2009;Prakash et al, 2013;Sarbajna et al, 2013). Ferric iron is known to expand the stability of sapphirine to lower temperatures (e.g.…”

Short-lived high-temperature prograde and retrograde metamorphism in Shaerqin sapphirine-bearing metapelites from the Daqingshan terrane, North China Craton

“…Sapphirine occurring in a silica-saturated but oxidizing system recording non-UHT conditions sets a precedent, although numbers of Spr-Spl-Bt-bearing, but Qz-absent rocks, have been obtained temperatures less than 900 • C (e.g. Nasipuri et al, 2009;Prakash et al, 2013;Raith et al, 2008;Sharma and Prakash, 2008;Sarbajna et al, 2013), and even down to 750 • C (Kruckenberg and Whitney, 2011), as reviewed in Kelsey and Hand (2015).…”

Characterisation of Eluvial Corundum (Ruby) from Kermunda, Kalahandi District, Odisha, India

“…It is relatively common in metamorphic rocks and its P-T stability domain is vast. Sapphirine is a metamorphic mineral and occurs in rocks of granulite facies metamorphism of Mg-Al rocks containing cordierite, phlogopite, corundum, garnet, gedrite, cummingtonite, orthopyroxene, spinel and aluminosilicate minerals [7]. On the basis of texture, grain contact and mineral association in the Mg-Al rich rocks several types of metamorphic reactions have been proposed for the formation of these minerals [8][9][10].…”

“…The following reactions singularly or in combination might have given rise to the observed corundum-spinel textural features. The reactions are: (a) Phlogopite + Corundum = Spinel + K-feldspar +water [7] or (b) Corundum + Garnet = Spinel.…”