TSANGPOITE: THE UNKNOWN CALCIUM SILICO PHOSPHATE PHASE IN THE ANGRITE D´ORBIGNY.

HWANG S.L.; SHEN P; CHU, H-T; YUI T.F.; VARELA, M.E; IIZUKA Y.

Houston

Conferencia; Lunar and Planetary Science Conference; 2016

The unusual calcium silico phos-phate (CSP) has been found in several angrites i.e., Asuka 881371 [1, 2], Sahara 99555 [3], D.Orbigny [4-7] and NWA 2999 [8]. It has a low modal abundance (< 1 vol.%) and was found in several textural settings [1-7] associated with late-stage crystallization minerals such as troilite, ulvöspinel and kirschsteinite. It also occurs as euhedral inclusions or lathy grains in titanif-erous and aluminous hedenbergite [7, 9, 10]. Previous studies show that the CSP is similar in composition to silicocarnotite, Ca5(PO4)2SiO4 and nagelschmidtite, Ca7(SiO4)2(PO4)2. However, the structure of CSP dif-fers form that of the previous phases and seems to be isostructure to apatite [11].Here we report about the new mineral tsangpoite (2014-110) [12] an hexagonal polymorph of silicocar-notite, which was described as silica-phosphate in the angrite D?Orbigny [7, 9, 10]. This component can help to understand the cooling processes involved in the genesis of these rocks.