Petrogenesis of the Chagangnuoer deposit,NW China:a general model for submarine volcanic-hosted skarn iron deposits  

赋存在火山岩中的矽卡岩型铁矿成因新认识:新疆查岗诺尔铁矿的研究(英文)

作　　者：孙文礼 牛耀龄 马玉鑫 刘益 张国瑞 胡振兴 张照伟 陈硕 李继永 王晓红 龚红梅 

机构地区：[1]School of Earth Sciences, Lanzhou University [2]Institute of Oceanology, Chinese Academy of Sciences [3]Gansu Industry Polytechnic College [4]Department of Earth Sciences, Durham University [5]China University of Geosciences [6]Xi’an Center of Geological Survey

出　　处：《Science Bulletin》2015年第3期363-379,I0002,共18页科学通报（英文版）

基　　金：supported by two geological survey projects of China Geological Survey Departments and Offices (1212011121092, 1212011220928)

摘　　要：The Chagangnuoer deposit is a typical submarine volcanic rock-hosted skarn iron deposit, where orebodies mainly occur in andesitic rocks of the Dahalajunshan Formation （DF） with skams well developed around orebodies. The volcanic rocks of the DF in the Chagangnuoer deposit display calc-alkaline characteristics. The ore-bearing andesitic rocks have high ^87Sr/^86Sr（i） （0.7058-0.7117） and low εNd（t） （-3.51 to 1.67）. They probably formed through mixing of basaltic melts and the induced crustal melts. LA-ICP-MS U-Pb zircon ages of 250 and 305 Ma are obtained for the granite and granodiorite in the Chagangnuoer deposit, respectively, which are signifi- cantly younger than the timing of the skarn formation （316 Ma）. These age data indicate that the granitoids have no contribution to the skarn and associated iron mineralization. This paper proposes a new genetic model for submarine volcanic rock-hosted skam iron deposits, in which the iron mineralization, skarn formation and volcanic magmatism are necessary aspects of the same system; the iron separates and concentrates from the silicate magma in the form of Fe（II） carbonate complex. While this conceptual model is largely based on observations on the Chagangnuoer deposit, it may have general significance for skam-type iron deposits associated with submarine volcanic rock sequences and warrants further testing and improvement.查岗诺尔铁矿是一个典型的赋存在海相火山岩中的矽卡岩型铁矿矿体主要赋存在石炭纪大哈拉军山组的安山质火山岩中，矿体周围广泛地发育矽卡岩查岗诺尔铁矿的赋矿围岩（安山质火山岩）具有高的^87Sr／^86Sr（i）（07058～0．7117）和较低的εNd（t）（-3．51～1．67）．本文认为这些安山质火山岩的母岩浆是玄武质岩浆混染地壳物质的产物．锆石U-Ph定年研究表明查岗诺尔铁矿区发育的侵入岩主要有两期：305Ma的花岗闪长岩和250Ma的花岗岩．侵入岩活动时间明显晚于矽卡岩形成时间（～316Ma），所以矿区侵入岩对于矽卡岩的形成和相关铁矿化没有贡献．对于赋存在火山岩中矽卡岩型铁矿的成因，本文提出新认识：（1）矽卡岩的形成、铁矿化和火山岩浆活动是一个系统的不同表现；（2）铁以碳酸亚铁络合物的形式从硅酸岩浆中分离和富集，虽然该模型仅建立在查岗诺尔铁矿的研究之上，但是对于理解同类矿床成因具有重要意义，所以有必要进一步完善．

关 键 词：Volcanic rocks-hosted skam iron deposit Petrogenesis of ore-bearing andesitic rocks U-Pb zircon ages New genetic model 

分 类 号：P618.31[天文地球—矿床学]