山东鲁东地区中生代构造–岩浆事件与金矿成矿作用

Abstract

山东鲁东地区处于特提斯、古亚洲洋和太平洋三大构造域的结合部位，它们的相互作用过程决定并影响着鲁东的成矿环境，在中生代区内有印支和燕山二次造山事件。燕山造山事件在鲁东地区表现为三个造山幕，每一幕表现为挤压与伸展的旋回性，这种旋回性是鲁东金矿和多金属矿成矿的地质背景。中生代构造演化对山东的构造–岩浆事件、沉积环境和成矿作用起着制约与控制作用，岩浆–沉积–构造–成矿事件与区域构造事件具有相互耦合性，金矿、多金属矿的形成与定位同燕山期三个构造幕紧密相联，3期成矿事件160~140 Ma、130~110 Ma和105~80 Ma则与玲珑、郭家岭和伟德山岩体的构造–岩浆热事件相耦合。文章在统计区内已报道的金矿成矿年龄样品318件的基础上，划分了81~105 Ma、110~130 Ma和141~160 Ma三个年龄集中区间，按照成矿作用、矿床类型和成矿时序，认为区内成矿作用与三个构造幕同步，为第一幕Mo-W-Au、第二幕Au-Ag和第三幕Cu-Pb-Zn-Mo-Au成矿作用。Mo-W-Au成矿系列典型矿床是邢家山钼钨矿、铜矿和留村金矿；Au-Ag成矿系列是鲁东地区主成矿期的表现形式，可进一步分为与早白垩世壳幔岩浆作用有关的Au、Ag矿床成矿亚系列、与早白垩世壳幔岩浆作用有关的Au、Ag、Cu、多金属矿床成矿亚系列和与早白垩世壳幔岩浆期后热液活动有关的Cu、Au、Fe、Ag、硫铁矿矿床亚系列，其典型矿床为焦家金矿、三山岛金矿和玲珑金矿等。Cu-Pb- Zn-Mo-Au成矿系列与伟德山造山晚期闪长岩–花岗闪长岩–花岗岩组合、浅成–超浅成石英闪长玢岩–花岗闪长斑岩–石英二长玢岩组合和青山群石前庄组中酸性火山喷发建造关系密切，是区内金矿的叠加成矿期及多金属矿的主成矿期，成矿年龄81~105 Ma。 Eastern Shandong Province is situated at the intersection of three tectonic domains as Tetisi, Paleo-Asian Ocean and Pacific Ocean. Interaction process of these three global tectonic domains control and affect the metallogenic environment of eastern ShandongProvince. This area has experienced lndosinian orogenic event and Yanshanian oro- genic event during Mesozoic period. Yanshanian orogenic event represents three tectonic episodes. Each episode repre- sents cyclicity of extrusion and extension. This cyclicity is the geological background of mineralization in Ludong gold deposit and other polymetallic deposits. Mineralization geological environment of three world-class gold fields with the reserve over one thousand tons, such as Sanshaodao gold field, Jiaojia gold field and Linglong gold field have the char- acteristics of uniqueness and induplication. Mesozoic tectonic evolution controls tectonic-magmatic event, sedimentary environment and gold mineralization. There is a strong coupling relationship between magma-sedimentary-tectonism -mineralization event and regional tectonic evolution. The formation and location of gold deposits and polymetallic deposits also have close connections with three tectonic episodes of Yanshanian orogenic event. Three mineralization events (160 - 140 Ma, 130 - 110 Ma and 105 - 80 Ma) have coupling relationship with three regional tectonic-magmatic hydrothermal events of Linglong rock mass, Guojialing rock mass and Weideshan rock mass respectively. On the basis of gold mineralization ages gained from 318 samples which have been reported in this area, three age concentration periods have been divided as 81 - 105 Ma, 110 - 130 Ma and 141 - 160 Ma. According to mineralization, deposit types and ore-forming sequences, it is regarded that mineralization in this area is synchronous with three tectonic episodes. That is the first Mo-W-Au tectonic episode, the second Au-Ag tectonic episode and the third Cu-Pb-Zn-Mo-Au tectonic episode mineralization. Typical deposits of Mo-W-Au metallogenic series are Xiangjiashan molybdenum and tungsten deposit, copper deposit and Liucun gold deposit. Au-Ag metallogenic series are major representative type of main min- eralization stages in eastern Shandong Province. It can be further divided into Au-Ag metallogenic sub-series which has close relation with mantle-crust magma interaction in early Cretaceous period; Au-Ag-Cu metallogenic sub-series which has close relation with mantle-crust magma in early Cretaceous period; and Cu-Au-Fe-Ag metallogenic sub-se- ries which has close relation with post-magmatic hydrothermal in early Cretaceous period. Typical deposits are Jiaojia gold deposit, Sanshandao gold deposit and Linglong gold deposit. Cu-Pb-Zn-Mo-Au metallogenic series is the main stage of superimposition mineralization and polymetallic mineralization with a mineralization age at 81 - 105 Ma. This series is closely related to the diorite-granodiorite-granite and quartz diorite porphyry-granodiorite porphyry-monzonite porphyry of the late Weideshan orogenic stage, and acid-intermediate volcanic-sedimentary formation of Shiqianzhuang formation in Qingshan Group.