辽宁鞍本地区铁质活化再富集成因富铁矿的成矿时代——齐大山铁矿床辉钼矿Re-Os年龄证据

发布时间：2018-08-02 07:23

【摘要】：中国与早前寒武纪条带状铁建造有关的磁铁富矿集中分布在辽宁鞍本地区,主要由条带状铁建造经过后期热液改造而成,有去硅富铁和铁质活化再富集2种成因,前者以弓长岭铁矿床二矿区的富铁矿为代表,富铁矿的成矿时代为1.84 Ga左右;后者以齐大山铁矿床樱桃园矿区的富铁矿(樱桃园富铁矿)为代表,但是该富铁矿的成矿时代还不清楚。为了探讨铁质活化再富集型富铁矿的成矿时代,笔者对齐大山铁矿区的辉钼矿进行Re-Os同位素测年。该矿区的辉钼矿有3种产出方式:第一种产于花岗伟晶岩中,呈巨晶辉钼矿集合体;第二种为蚀变岩中石英透镜体边部薄膜状辉钼矿;第三种产于混合花岗岩中的石英脉中,呈浸染状产出。第一种辉钼矿的年龄(2503±33)Ma~(2538±36)Ma,代表了条带状铁建造铁质活化再富集形成富铁矿的主要时期,形成于2.5 Ga左右的华北克拉通发生岩浆、变质作用与克拉通化时期,钼来自地壳,佐证了新太古代末华北克拉通的第一次克拉通化主要是壳内物质的重组;第二种辉钼矿的年龄为(2088±28)Ma,其成矿物质来自地壳,佐证了华北克拉通2.3~1.95 Ga的裂谷-俯冲-增生-碰撞的陆内造山事件也主要是壳内物质的重组;第三种辉钼矿的年龄为(1834±28)Ma~(1853±29)Ma,与弓长岭二矿区"去硅富铁"型富铁矿的成矿时代一致,其成矿物质来自地壳,但混有地幔组分,佐证了1.85~1.65 Ga的华北克拉通基底抬升、镁铁质岩墙群侵入、裂陷槽和裂谷形成有地幔物质的参与。
[Abstract]:The magnetite deposits associated with the early Precambrian banded iron formation in China are concentrated in the Anben area of Liaoning Province, and are mainly formed by the late hydrothermal transformation of the strip iron formation. There are two causes of desilication of iron rich in iron and activation and reenrichment of iron. The former is represented by the rich iron ore in the second mining area of the Gongchangling iron deposit, and the ore-forming age of the ore-rich ore is about 1.84 Ga, while the latter is represented by the rich iron ore in the Sakuraoyuan mine of Qidashan iron deposit. But the ore-forming age of the iron ore is not clear. In order to study the metallogenic age of iron ore enriched by activation and reconcentration, Re-Os isotopic dating of molybdenite in Qidashan iron ore area was carried out. There are three kinds of molybdenum deposits in this area: the first occurs in granitic pegmatite as megacrystalline molybdenum aggregates, the second is thin film molybdenum at the edge of quartz lens in altered rocks, and the third occurs in quartz veins in mixed granite. The product is dyed. The age of the first molybdenum deposit is (2503 卤33) Ma ~ (2538 卤36) Ma, which represents the main stage of iron activation and reenrichment to form iron ore rich in iron ore, and formed in the North China Craton (about 2.5 Ga) where magma occurred, metamorphism and cratonization occurred, and molybdenum came from the earth's crust. It is proved that the first cratonization of the North China Craton in the late NeoArchaean was mainly the recombination of the material in the crust, and the second molybdenum was (2088 卤28) Ma.The ore-forming material came from the crust. The results show that the intracontinental orogenic events of rift, subduction, accretion and collision in the North China Craton are also mainly the recombination of materials in the crust, and the age of the third molybdenum deposit is (1834 卤28) Ma ~ (1853 卤29) Ma, which is consistent with the ore-forming age of the "desilication and iron rich" type iron ore deposit in the Gongchangling No. 2 deposit, and the ore-forming age of the third molybdenum deposit is (1834 卤28) Ma ~ (1853 卤29) Ma. The ore-forming materials come from the crust, but they are mixed with mantle components, which proves that the North China Craton basement uplift of 1.85 ~ 1.65 Ga, the intrusion of mafic dike group, and the formation of rift trough and rift valley involve mantle material.
【作者单位】：辽宁省冶金地质勘查局地质勘查研究院;中国科学院地质与地球物理研究所;中国地质科学院矿产资源研究所国土资源部成矿作用与资源评价重点实验室;
【基金】：国家“973”项目(编号:2012CB416801) 国土资源部公益性行业科研专项(编号:200911007-15、201111002)联合资助
【分类号】：P618.31

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