宁芜地区矿田构造–建造特征与成矿控制分析

Metallogenic Geological Characteristics and Ore-Controlling Factors of the Ore Fields in Nanjing-Wuhu Basin

摘要: 长江中下游宁芜地区是中国著名的铁–铜矿集区，也是我国玢岩型铁矿床成矿模式及相关理论的发祥地。近年来，通过深部找矿及整装勘查工作，宁芜地区取得了一系列地质及找矿的新进展，对其矿田的构造–建造与成矿控制也有新的认识。梅山矿田是受大王山组火山碎屑岩–熔岩与偏碱性玄武安山质辉长闪长(玢)岩建造控制形成的岩浆内接触带型铁矿床；凹山矿田则是以大王山组火山构造为基础的隐爆角砾岩带与隐爆角砾岩筒岩石建造控制的隐爆角砾岩型铁矿床；姑山矿田是受周村冲组碳酸盐岩与钠质石英闪长岩建造控制的层控接触带型铁矿床；后期的铜井矿田则是NE向断裂制约下，由娘娘山组碱性火山岩与辉石正长斑岩含矿建造控制的热液型脉状铜金矿床。它们的形成是宁芜火山岩盆地走滑剪切发育过程中构造、岩浆共同控制的结果，受盆地构造和火山构造的双重制约，在中基性–碱性火山–潜火山岩的成矿建造中，铁–铜矿床形成于晚白垩世的130~123 Ma间。

Abstract: Nanjing-Wuhu basin, located at the middle and lower reaches of the Yangtze River, is a notable iron and copper ore concentration area in China. As the field base for studying the metallogenic model of China’s porphyritic iron deposits, recent years’ deep-seated ore prospecting and integrated ex-ploration in this area have achieved significant progress and made a breakthrough. Through pro-found research on four typical ore fields in Nanjing-Wuhu basin area, this paper summarizes the metallogenic characteristics in terms of the structures and constructions of the ore fields, further discusses the metallogenic control and evolution, and proposes suggestions for prospecting orien-tation on the deep-seated and the outside of mineralized fields. Among the four ore fields, Meishan ore-field is occurred with magmatic contact-metasomatic iron and copper deposits dominated by volcaniclastics and lava of Dawangshan Formation, and alkaline basaltic andesitic gabbrodioritic phyrite-gabbrodiorite; Washan ore-field that magmatic contact-metasomatic iron and copper de-posits are dominated by cryptoexplosive breccia zones and cryptoexplosive breccia pipes within Dawangshan Formation volcanic structure; Gushan ore-field is a type of contact metasomatic iron deposits with dominant contact zone between carbonatites and sodic quartz diorites of Zhoucun-chong Formation; The mineralization of Tongjing ore-field is due to that the alkaline volcanic rock and pyroxene orthophyre rock mass in Niangniangshan Formation are controlled by NE trending faults. According to the above research, the paper proposes the metallogenic control factors and constraints of the iron and copper deposits in Nanjing-Wuhu basin. The time of mineralization ranges between 130 - 123 Ma.