XIE Lan-fang, CHEN Hong-yi^*, MIAO Bing-kui

(1. Guangxi Key Laboratory of Hidden Metallic Ore Deposits Exploration, Guilin 541006, China;
2. Guangxi Key Laboratory of Planetary Geological Evolution, Guilin 541006, China;
3. Research Center of Meteorites and Planetary Materials, Guilin University of Technology, Guilin 541006, China)

Abstract: Many kinds of metal sulfides in enstatite chondrites were formed under the extremely reduced conditions of the early solar nebula. GRV 13100 is an enstatite chondrite found by CHINARE in the Grove Mountain of Antarctic. The opaque minerals (of metal sulfides and phosphides) include troilite, daubreelite, niningerite, oldhamite, Si-bearing kamacite, schreibersite, and perryites, with content of up to 21%. They are experienced a certain degree of thermal metamorphism. Based on detailed studies on the petrographical and mineralogical characteristics of the GRV 13100 enstatite chondrite and the comparison with other EH and EL chondrites, the following conclusions are achieved. (1) The FeS content of the niningerite can reflect the metamorphic temperature of its parent body. Base on FeS contents of niningerites in the GRV 13100 chondrite, the thermal metamorphic temperatures are mostly varied from 200℃ to 300 ℃, with a few exceptions of 400－800 ℃, which could be caused by external inhalation or could represent condensation or crystallization temperatures of the primitive nebula. (2) The niningerite was formed after the crystallization of olivine and enstatite in the process of direct condensation of the solar nebula. (3) There are petrogenetic and secondary two kinds of troilite. The protogenetic one was formed due to the condensation of solar nebula. The secondary one was formed via the sulfuration of iron and nickel metals or decomposition of niningerite in the late thermal metamorphic process. (4) The perryite was possibly exsolved from the Si-bearing kamacite. This work provides constraints for the evolution of highy reduced nebula in the early solar system and the late thermal metamorphism of the solar system.

Keywords: Enstatite chondrite; GRV 13100; Niningerite; Troilite; Genetic mechanism

ACTA MINERALOGICA SINICA Vol. 40, No.1, 2020, page 83-91