山东胶东矿集区中生代构造事件与金矿成矿作用

Mesozoic Tectonic Events and Mineralization of Gold Deposits in Jiaodong Area in Shandong Province

摘要:

中生代胶东地区有2次重要的碰撞造山事件，印支造山作用主要表现为扬子板块向华北板块俯冲，形成苏鲁高压—超高压变质带，同造山花岗岩及后造山高碱正长岩；燕山造山作用的大陆动力学环境起源于中亚特提斯构造域向滨太平洋构造域转化和太平洋板块的俯冲，在胶东地区表现为3幕4期构造岩浆事件并以3次造山和3次伸展为特征。胶东地区中生代构造岩浆沉积成矿事件序列的时空演化也受控于这一地质作用过程，尤其是侏罗纪至白垩纪这一阶段，是胶东地区构造活动、岩浆侵入、地层沉积、火山喷发和成矿作用爆发时期，是挤压、伸展交互转化时期。该文基于对中生代构造事件的研究，厘定了构造与金矿成矿作用在空间上和时间上的高度耦合性。研究发现胶东地区在侏罗纪至白垩纪一阶段构造活动由早到晚经历了4期6阶段挤压伸展过程，第一期近S—N向挤压及NW—SE向挤压，第二期早阶段NE—SW向挤压晚阶段NE—SW向引张，第三期NW向引张，第四期近E—W向挤压及近S—N向引张，与构造—热事件相一致；在金矿成矿作用方面，表现为3期金矿成矿作用，对应于由挤压向伸展转变阶段的成矿作用过程，即第一幕伸展后的早期金矿成矿作用、第二幕伸展后的金矿主成矿期和第三幕伸展后的叠加金矿成矿作用。这种挤压—伸展构造活动的相互转化互为因果，挤压为伸展提供了条件，伸展为金矿的沉淀提供了空间，也为下一次的挤压提供了前提，并伴随着与岩浆—构造事件紧密相关的不同的成矿作用，构成了挤压—伸展的构造—岩浆—成矿作用方式，这是胶东地区形成大型、超大型金矿的动力学条件。

Abstract:

There are two important collisional events in Jiaodong area. Indosinian orogeny is mainly presented as the subduction from Yangtze plate to the North China plate, which formed Sulu HPUHP metamorphic belt, synorogenic granites and post orogenic high alkali syenites. Dynamic environment of continental Yanshan orogeny came from the transformation of ethys tectonic domain in central Asia to the Pacific tectonic domain and the subduction of the Pacific plate. It represented as 3 periods and four stages tectonic magmatic events in Jiaodong area with the characteristics of three orogenic stages and three extension. Time and space evolution of Mesozoic tectonic structures—magma—sedimentary mineralization event series in Jiaodong area is also controlled by the geological processes, especially the stage from Jurassic to Cretaceous. This stage is the eruption period of tectonic activity, magma intrusion, strata sedimentary, volcano eruption and mineralization, it is also reciprocal transformation of extrusion and stretching period in Jiaodong area. Based on the study of Mesozoic tectonic events, high coupling between structures and the mineralization of gold deposits in space and time has been defined. It is found that Jiaodong area has experienced 4 periods and 6 stages extrusion—stretching process from Jurassic to Cretaceous. The first stage is the extrusion with the trend of nearly S—N and NW—SE. The second stage is the extrusion with the trend of NE—SW in early period and the extrusion with the trend of NE—SW in late period. The stage is the extrusion with the trend of NW, The fourth stage is the extrusion with the trend of nearly E—W and the compression with the trend of S—N, which is consistent with tectonic thermal events. In terms of gold mineralization, it is showed as three gold mineralization, and corresponding to the transition from compression to extension mineralization, that is early gold mineralization agter the first stretching stage, gold mineralization after the second stretching stage, and gold mineralization after the third stretchingand superposition stage. The mutual transformation of extrusion and extensional tectonics is reciprocal causation. Extrusion provides conditions for the extension, while extension provides space for the gold deposits. It also provides the premise for next extrusion, accompaning with different mineralization which has close relation with magma tectonic events. It formed extrusion—stretching structure—magma—mineralization. This is the dynamics conditions of large and super large gold deposits formed in Jiaodong area.