干旱区生态环境知识资源中心(Arid): The alteration history of the CY chondrites, investigated through analysis of a new member: Dhofar 1988

Arid

DOI	10.1016/j.gca.2020.11.008
	The alteration history of the CY chondrites, investigated through analysis of a new member: Dhofar 1988
	Suttle, M. D.; Greshake, A.; King, A. J.; Schofield, P. F.; Tomkins, A.; Russell, S. S.
通讯作者	Suttle, MD (corresponding author), Nat Hist Museum, Dept Earth Sci, Planetary Mat Grp, Cromwell Rd, London SW7 5BD, England.
来源期刊	GEOCHIMICA ET COSMOCHIMICA ACTA
ISSN	0016-7037
EISSN	1872-9533
出版年	2021
卷号	295 页码:286-309
英文摘要	We provide the first detailed analysis of the carbonaceous chondrite Dhofar (Dho) 1988. This meteorite find was recovered in 2011 from the Zufar desert region of Oman and initially classified as a C2 ungrouped chondrite. Dho 1988 is a monomict breccia composed of millimetre-sized clasts, between which large (similar to 50-250 mu m) intermixed sulphide-Ca-carbonate veins formed. It has high sulphide abundances (similar to 14 vol%), medium-sized chondrules (avg. 530 mu m = 33), relatively low chon- drule/CAI abundances (<20 area%), a heavy bulk O-isotope composition (delta O-17 = 9.12%e, delta O-18 = 19.46 parts per thousand) and an aqueously altered and then dehydrated alteration history. These characteristics are consistent with the newly defined Yamato-type (CY) carbonaceous chondrite group, suggesting this meteorite should be reclassified as a CY chondrite. Dho 1988 experienced advanced aqueous alteration [petrologic subtype 1.3 in the scheme of Howard et al. (2015)]. Alteration style and extent are similar to the CM chondrite group, with the matrix having been replaced by tochilinite-cronstedtite intergrowths and chondrules progressively pseudomorphed by phyllosilicates, sulphides and in one instance Ca-carbonates. However, departures from CM-like alteration include the replacement of chondrule cores with Al-rich, Na-saponite and upon which Cr-spinel and Mg-ilmenite grains precipitated. These late-stage aqueous alteration features are common among the CY chondrites. Fractures in Dho 1988 that are infilled by phyllosilicates, sulphides and carbonates attest to post-brecciation aqueous alteration. However, whether aqueous alteration was also active prior to brecciation remains unclear. Veins are polymineralic with a layered structure, allowing their relative chronology to be reconstructed: intermixed phyllosilicate-sulphide growth transitioned to sulphide-carbonate deposition. We estimate temperatures during aqueous alteration to have been between 110 degrees C < T < 160 degrees C, based on the co-formation of Na-saponite and tochilinite. Dho 1988 was later overprinted by thermal metamorphism. Peak temperatures are estimated between 700 degrees C and 770 degrees C, based on the thermal decomposition of phyllosilicates (both serpentine and saponite) combined with the survival of calcite. As temperatures rose during metamorphism the thermal decomposition of pyrrhotite produced troilite. Sulphur gas was liberated in this reaction and flowed through the chondrite reacting with magnetite (previously formed during aqueous alteration) to form a second generation of troilite grains. The presence of both troilite and Ni-rich metal in Dho 1988 (and other CY chondrites) demonstrate that conditions were constrained at the iron-troilite buffer. (C) 2020 Elsevier Ltd. All rights reserved.
英文关键词	Asteroids CY chondrites Thermal metamorphism Aqueous alteration
类型	Article
语种	英语
收录类别	SCI-E
WOS记录号	WOS:000614115300016
WOS类目	Geochemistry & Geophysics
WOS研究方向	Geochemistry & Geophysics
资源类型	期刊论文
条目标识符	http://119.78.100.177/qdio/handle/2XILL650/347921
作者单位	[Suttle, M. D.; King, A. J.; Schofield, P. F.; Russell, S. S.] Nat Hist Museum, Dept Earth Sci, Planetary Mat Grp, Cromwell Rd, London SW7 5BD, England; [Greshake, A.] Leibniz Inst Evolut & Biodiversitatsforsch, Museum Nat Kunde, Invalidenstr 43, D-10115 Berlin, Germany; [King, A. J.] Open Univ, Planetary & Space Sci, Walton Hall, Milton Keynes MK7 6AA, Bucks, England; [Tomkins, A.] Sch Earth Atmosphere & Environm, Melbourne, Vic, Australia
推荐引用方式 GB/T 7714	Suttle, M. D.,Greshake, A.,King, A. J.,et al. The alteration history of the CY chondrites, investigated through analysis of a new member: Dhofar 1988[J],2021,295:286-309.
APA	Suttle, M. D.,Greshake, A.,King, A. J.,Schofield, P. F.,Tomkins, A.,&Russell, S. S..(2021).The alteration history of the CY chondrites, investigated through analysis of a new member: Dhofar 1988.GEOCHIMICA ET COSMOCHIMICA ACTA,295,286-309.
MLA	Suttle, M. D.,et al."The alteration history of the CY chondrites, investigated through analysis of a new member: Dhofar 1988".GEOCHIMICA ET COSMOCHIMICA ACTA 295(2021):286-309.