山东莱芜地区中生代侵入杂岩特征与成矿关系

Characteristics of the Mesozoic intrusive complexes and their relation to metallogeny in Laiwu area,Shandong Province

山东莱芜地区燕山晚期岩浆活动强烈,形成了基性-中性-中偏碱性-酸性岩类侵入杂岩,岩体多沿盆地边缘分布,由北向南分别为金牛山杂岩体、矿山杂岩体、崅峪杂岩体及铁铜沟杂岩体,具有分布集中、时间短、岩石类型多样等特征,是一套偏铝质的钙碱性-碱钙性基性、中性、中酸性、酸性岩石组合类型,形成于中生代早白垩世。该杂岩岩浆来源于上地幔,并有古老地壳物质的参与。区内不同杂岩体从早到晚共有5次侵入,空间分布上,多在第一次侵入的辉石闪长岩及少量第四次侵入的二长闪长岩与碳酸盐岩的接触带上;时间上,主要成矿期在第四次侵入的二长闪长岩形成以后,属于整个岩浆演化序列的晚期阶段,并被多次侵入、多次成矿。岩体顶面形态的变化是控制矿床(体)的因素之一,特别是岩体的凹面、楔槽、凹面与凸面之间、岩体呈弧形上隆部位,均是形成接触交代(矽卡岩)型铁矿床(体)的有利部位。

The strong late Yanshanian magma activity in Laiwu of Shandong Province contributed to the formation of the basic-intermediate-intermediately-subalkalic-acid intrusive complexes.Distributed along the edge of the basin,they are the Jinniushan complex,the Mine complex,the Jiaoyu complex and the Tietonggou complex from north to south.Featured with concentrated distribution,fast formation,various rock types,these early Cretaceous-formed complexes are classified as a metaluminous set of calcium-alkalic-alkalic-calcium,basic,intermediate,intermediately acidic and acidic rock combination.The magma was derived from the upper mantle and ancient crustal material was involved in the formation.There were 5 intrusions one after another:spatially,the iron ore body of the study area were distributed in the first intrusion of pyroxene diorite and the contact zone of the fourth intrusion of monzodiorite and carbonate rock;the major metallization occurred after the formation of the fourth intrusion of monzodiorite,which was the late stage of magmatic evolutionary sequence and was repeatedly invaded and mineralized.The change of the shape of the top surface of the rock body is one of the factors controlling the deposit(body),especially the concave surface,wedge,the in-between of concave and convex surfaces,and the arc-shaped uplift of the rock body,which are favorable for forming contact metasomatic(skarn)iron deposit(ore body).