论南岭成矿带大宝山斑岩型铜矿的特殊性及其勘查意义

The Discussion on Particularity and Prospecting Significance of the Dabaoshan Porphyry Copper Deposit in the Nanling Metallogenic Belt

广东省大宝山矿床是南岭成矿带唯一的大型铜多金属矿床,此次研究在矿区中南部发现了细脉浸染状铜矿的新类型。为确定其是否为斑岩型铜矿的成因类型,本文在梳理南岭成矿带铜成矿条件和成矿规律的基础上,查明了矿区中南部英安斑岩的蚀变和铜矿化特征。综合研究认为南岭成矿带早侏罗世中酸性斑岩的小岩体较多,叠加多期断裂构造和碳酸盐岩建造,非常有利于铜多金属成矿物质的运移、富集。大宝山英安斑岩发育黑云母化、钾长石化、青磐岩化、绢英岩化、泥化等蚀变类型,铜矿化与绢英岩化、绿泥石化关系密切。大宝山铜矿中的英安斑岩沿逆冲推覆构造侵位并呈岩墙状产出,冷却过程中受区域构造应力产生了一组平行裂隙,岩浆房去气作用排出的热液沿裂隙蚀变围岩并充填成矿。大宝山斑岩型铜矿取得的找矿勘查成果表明,“全位成矿,缺位找矿”理念可以有效指导靶区圈定和老矿山外围(深部)找矿勘查,早侏罗世的南岭具有形成较大规模斑岩型铜矿的条件。

The Dabaoshan deposit in Guangdong Province is the only large scale copper polymetallic deposit in the Nanling metallogenic belt.In this study,a new type of veinlet disseminated copper deposit has been discovered in the central and southern part of this deposit.In order to determine whether it is the genetic type of porphyry copper deposits,this paper,on the basis of copper mineralization conditions and rules in the the Nanling Mountain metallogenic belt,has identified the alteration and copper mineralization characteristics of dacite porphyry in the central and southern part of the mining area.Comprehensive research reveals that the Nanling metallogenic belt contains numerous small bodies of Early Jurassic intermediate-acid porphyry,and that the coexistence of multiple-stage fault structures and carbonate formation is very conductive to the migration and enrichment of copper polymetallic minerals.The Dabaoshan dacite porphyry develops alteration types such as biotitization,potash feldspathization,propylitization,sericitization and argillization.The copper mineralization is closely related to sericitization and chloritization.The dacite porphyry in the Dabaoshan copper deposit was emplaced along the thrust nappe structure and produced in the form of dykes.Due to localized tectonic stress,a series of parallel cracks developed throughout the cooling phase.The ore was filled with the thermal fluid that was released during the degassing of magma chamber,which also altered the surrounding rock along the fractures.The prospecting and exploration findings of the Dabaoshan porphyry copper mine demonstrate that the concept of"all-site metallogenesis,absent site prospecting"may effectively direct target area delineation and prospecting in the periphery(deep)of old mines.The Early Jurassic Nanling metallogenic belt holds the conditions to form large scale porphyry copper deposits.