辽宁大石桥菱镁矿床的碳氧同位素组成和成因

CORC > 北京大学 > 地球与空间科学学院

	辽宁大石桥菱镁矿床的碳氧同位素组成和成因; The C-O isotope geochemistry and genesis of the Dashiqiao magnesite deposit, Liaoning Province, NE China
	汤好书 ; 武广 ; 赖勇
刊名	岩石学报
	2009
关键词	Lomagundi事件大石桥菱镁矿矿床辽河群 C-0同位素体系成因 Lomagundi Event Dashiqiao magnesite deposit Liaohe Group C-O isotope systematics Origin
英文摘要	在2.33～2.06Ga期间,δ~(13)C_(carb)发生了地质历史上最强烈的正异常事件,被称为Lomagundi事件。辽河群形成于2.3～1.85Ga期间,其大石桥组蕴涵超大型的大石桥菱镁矿矿床,在矿区厚约1144m。为检验华北克拉通对Lomagundi事件响应,揭示大石桥菱镁矿的成因,本文报道我们最新获得的地球化学研究结果。大石桥菱镁矿6件下伏白云岩地层样品的CaO/MgO摩尔比为0.87～0.94,δ~(13)C_(carb)和δ~(18)O_(carb)值分别为0.6‰～1.4‰(平均1.2‰,V-PDB标准)和16.4‰～19.5‰(平均 18.2‰,SMOW标准);与世界正常海...; The positive delta(13)C(carb) excursion happened in 2.33 similar to 2.06 Ga is unique in the Earth's history, which is called as Lomagundi Event. Liaohe Group, Liaoning Province, was deposited in the time span of 2.3 similar to 1.85 Ga. Its Dashiqiao Formation hosts the giant Dashiqiao magnesite deposit and is 1144 to thick in the Dashiqiao orefield. To insight into the impact of Lomagundi event in the North China Craton and the genesis of the Dashiqiao giant magnesite deposit, this paper reports new results obtained from our geochemical study. The and delta(13)C(V-PDB) and delta(18)O(V-SMOW) values of six dolomite samples whose CaO/MgO(mol) ratios range from 0.87 similar to 0.94, range 0.6 parts per thousand similar to 1.4 parts per thousand and 16.4 parts per thousand similar to 19.5 parts per thousand, with averages of 1.2 and 18.2 parts per thousand, respectively. Compared to the normal marine carbonates in the world, the delta(13)C(V-PDB) values are higher, whereas the delta(18)O(V-SMOW), values are lower, suggesting that the primary sediments should possess positive delta(13)C(V-PDB) anomaly (possibly 4.2 parts per thousand) which reflects the impact of Lomagundi Event, and that the delta(13)C(V-PDB) and delta(18)O(V-SMOW) decreased in post-sedimentation diagenesis or/and regional metamorphism. The magnesite layer is >550 m thick and has CaO/MgO(mol) ratios ranging from 0.005 similar to 0.23. Its delta(13)C(V-PDB) and delta(18)O(V-SMOW) values are 0.1 parts per thousand similar to 0.6 parts per thousand and 9.2 parts per thousand similar to 12.7 parts per thousand, with averages of 0.4 parts per thousand and 10.9 parts per thousand (n = 6), respectively, obviously lower than those of the underlying dolomites. The depletions of (13)C and (18)O in magnesites relative to dolomites were interpreted to be the results of regional metamorphism-related hydrothermal alteration which resulted in rock recrystallization and mass exchange. This interpretation call be furthered by two particular samples, i.e. the hanging-wall dolomite and the veinlet-filled magnesite from ore layer. The hanging-wall dolomite contains mega-crystals of cylindrical talc which probably formed by local fluid-rock interaction between dolomite and siliceous fluid or between argillic dolomite and fluid. The talc-bearing dolomite has delta(13)C(V-PDB) ratio of -2.6 parts per thousand and delta(18)O(V-SMOW) value of 14.1 parts per thousand, respectively, indicating that the dolomite interacted with fluid poor in (13)C and (18)O and made its delta(13)C(V-PDB) and delta(18)O(V-SMOW) decreased again. The veinlet-filled magnesite yields delta(13)C(V-PDB) and delta(18)O(V-SMOW) values of -2.7 parts per thousand and 16.2 parts per thousand, respectively, showing lower delta 13C(V-PDB) and higher delta(18)O(V-SMOW) than the massive magnesite, strongly supporting that the massive magnesite interacted with low-delta(13)C fluids which are, possibly sourced from meteoric water at low temperature during post-ore time. Therefore, the formation of Dashiqiao magnesite deposit undervent primary, sedimentation diagenesis, regional metamorphism, fluid replacement as well as local post-ore alteration.; http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000265945400019&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701 ; SCI(E); 中文核心期刊要目总览(PKU); 中国科技核心期刊(ISTIC); 中国科学引文数据库(CSCD); 26; 02; 455-467; 25
语种	中文
内容类型	期刊论文
源URL	[http://ir.pku.edu.cn/handle/20.500.11897/175296]
专题	地球与空间科学学院
推荐引用方式 GB/T 7714	汤好书,武广,赖勇. 辽宁大石桥菱镁矿床的碳氧同位素组成和成因, The C-O isotope geochemistry and genesis of the Dashiqiao magnesite deposit, Liaoning Province, NE China[J]. 岩石学报,2009.
APA	汤好书,武广,&赖勇.(2009).辽宁大石桥菱镁矿床的碳氧同位素组成和成因.岩石学报.
MLA	汤好书,et al."辽宁大石桥菱镁矿床的碳氧同位素组成和成因".岩石学报 (2009).