[S-MP26] Supercontinents and Crustal Evolution

[SMP26-03] An analogue of Pink Moon from Fiskenæsset Complex, Greenland

*Krishnan Sajeev¹、Brian F Windley²、S Veni¹、Yann Sivry³、V.J. Rajesh⁴ (1.Centre for Earth Sciences, Indian Institute of Science、2.School of Geography, Geology and the Environment, University of Leicester, Leicester LE1 7RH, UK、3.Université Paris Cité, Institut de Physique du Globe de Paris, CNRS, F-75005, Paris, France、4.Department of Earth and Space Sciences, Indian Institute of Space Science and Technology, Valiamala, Thiruvananthapuram 695547, India)

キーワード：pink-spinel , Fiskenæsset Complex, Lunar pink Spinel

Moderately chromium-bearing magnesium end-member pink-spinel is not common in terrestrial rocks. However, they are reported from a few lunar rocks. Mg-spinel lithologies (~90% spinel) were reported from the lunar far side using Chandrayan-1 Moon Mineralogy Mapper (M³). An analogue to study such rock was yet to be identified from the Earth. We are presenting a monomineralic pink-spinel rock associated with anorthosite and amphibolite from the Fiskenæsset Complex, Greenland. The texture and composition of spinel (X_Mg = 94.8) in these samples are the same as that of the lunar examples (X_Mg = <92). The geological setting also has similarities. The spectral signatures of this lithology are similar to the M³ data. The uniform pink spinel grains have low-Cr, -V and high-Ga, -Li, indicating high partial pressure of oxygen. The EPR-MORB normalised gallium in uniform pink spinel has 1.5 times enrichment while most dark regions are 6 times depleted; this explains why spinel starts crystalising before plagioclase followed by equilibrium plagioclase (anorthosite) fractionation. The result of this study explains that the petrogenesis of Lunar M³ spinel rock must be through fractional crystallisation of high oxygen fugacity pockets in the high aluminium basaltic melt.