西坝岩体的成因及其在陕西双王金矿中的成矿作用
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摘要
在花岗岩原地重熔成因理论的基础上,对双王金矿的地质、地球化学和成矿学资料重新分析,认为西坝岩体的形成是该区地壳原地熔融或重熔的结果。微量元素和稀土元素配分特征表明,蚀变围岩残留了地层岩石的信息,而新生方解石、铁白云石等矿物则显示的是热液信息。双王金矿总体成矿过程是富金(亲硫元素)地层被卷入印支期地壳熔融事件,经重新分异后排出岩浆系统形成含矿热液,热液在运移过程中压裂地层形成角砾岩带容矿构造,而后在燕山早期—中期沉淀形成金矿床。从形成时间来看,若不考虑误差因素,燕山早期的金矿"成矿壳层"或已基本剥蚀殆尽,在目前的剥蚀深度上,出露的主要是燕山中期的"成矿壳层"中的金矿体。若考虑误差因素,现今金矿体测年时代可能并非由某一期岩浆热液的含金量的多寡引起,而是与两期持续过程的剥蚀深度有关。即在目前的剥蚀深度上,出露的是两期"成矿壳层"中的金矿体。
Based on the genetic theory of the in-situ granite re-melting,the authors re-analyzed the geological,geochemical and metallogenic data.It was found that the Xiba complex intrusion was formed by repeated crustal melting in the earlier Mesozoic period.Characteristics of trace elements and REE distribution pattern shows that the altered wall rock reservered stratum information and the new-formed minerals such as calcite and ankerite indicated that hydrothermal information involved.The mineralization process of Shuangwang gold deposit is summarized as followings:the high gold-bearing strata was involved in melting process of Indosinian period,and discharged from the magmatic system by the magmatic differentiation and resulted in formation of ore-bearing hydrothermal fluids,formed brecciaed structure in the compressive strata,and finally the Shuangwang gold orebodies were formed in early and middle Yanshanian period by the hydrothermal precipitation.
Based on the genetic theory of the in-situ granite re-melting,the authors re-analyzed the geological,geochemical and metallogenic data.It was found that the Xiba complex intrusion was formed by repeated crustal melting in the earlier Mesozoic period.Characteristics of trace elements and REE distribution pattern shows that the altered wall rock reservered stratum information and the new-formed minerals such as calcite and ankerite indicated that hydrothermal information involved.The mineralization process of Shuangwang gold deposit is summarized as followings:the high gold-bearing strata was involved in melting process of Indosinian period,and discharged from the magmatic system by the magmatic differentiation and resulted in formation of ore-bearing hydrothermal fluids,formed brecciaed structure in the compressive strata,and finally the Shuangwang gold orebodies were formed in early and middle Yanshanian period by the hydrothermal precipitation.
引文
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[4]陈国能.洛尼格拉佩斯.花岗岩成因:原地重熔与地壳演化[M].北京:中国地质大学出版社,2009.
[5]王可新.陕西省太白县双王金矿床地质地球化学特征及成因探讨[D].北京:中国地质大学(北京),2012.
[6]韩吟文,马振东.地球化学[M].北京:地质出版社,2003.
[7]胡西顺.陕西双王金矿床成因再认识[J].黄金科学技术,2009,17(2):17-27.
[8]王中刚,于学元,赵振华.稀土元素地球化学[M].北京:科学出版社,1989.
[9]王国富.陕西双王金矿床构造成矿作用及成矿预测研究[D].长沙:中南大学,2006.
[10]彭建堂,胡瑞忠,漆亮,等.锡矿山热液方解石的REE分配模式及其制约因素[J].地质评论,2004,50(1):25-32.
[11]姜莲婷,陈国能.副族元素的成矿作用与矿田类型[J].地学前缘,2011,18(1):95-101.
[12]林小明,陈国能.从离子半径变化看元素地球化学场中的成矿分带[J].中山大学学报,自然科学版,2002,41(5):91-94.
[13]张作衡,毛景文,李晓峰.双王角砾岩型金矿床地质地球化学及成矿机制[J].矿床地质,2004,23(2):241-252.
[14]谢玉玲,徐九华,何知礼,等.太白金矿流体包裹体中黄铁矿和铁白云石等子矿物的发现及成因意义[J].矿床地质,2000,19(1):54-60.
[15]李宏卫,娄峰,许冠军,等.多次重熔的成矿作用:对甘肃中川岩体成岩过程的再认识[J].地学前缘,2011,18(1):126-132.
[16]赵中和,刘峻岭,黄沙,等.陕西省双王金矿床8号矿体地质—地球物理—地球化学找矿模型、评价指标研究[R].陕西省地质矿产勘查开发局物化探队,1994.
[17]石准立,刘瑾璇,金勤海,等.与碱性碳酸盐岩有关的双王金矿[C]//秦巴金矿论文集.北京:地质出版社,1993.