鄂尔多斯盆地东部紫金山岩体特征与形成的动力学环境——盆地热力-岩浆活动的深部作用典型实例剖析  

Characteristics of the Zijinshan Complex and Its Dynamic Environment in the East of the Ordos Basin—Analysis of a Classic Example on the Deep Processes of Thermal-Magma Activity in the Basin

作　　者：杨兴科[1] 晁会霞[1] 张哲峰[1] 姚卫华[2] 董敏[1] 

机构地区：[1]长安大学西部矿产资源与地质工程教育部重点实验室,陕西西安710054 [2]中国石油长庆油田分公司勘探开发研究院,陕西西安710021

出　　处：《大地构造与成矿学》2010年第2期269-281,共13页Geotectonica et Metallogenia

基　　金：国家973项目(编号:2003CB214601)资助

摘　　要：在鄂尔多斯盆地动力学和热力作用讨论基础上,以紫金山岩体为代表,进行了鄂尔多斯盆地东部岩浆活动的深部地质背景、岩石学、地球化学、同位素年代学和构造演化等研究。认为盆地热力作用是盆地动力学研究的弱点和难点,盆地热力作用具明显非均一性,热力盆地特征复杂、类型多样,盆地热力构造可分为五类。针对盆地热力作用研究的薄弱性和其与深部圈层活动的复杂性及特殊性,提出了未来研究应注意的要点。中生代鄂尔多斯盆地为克拉通内改造叠合型盆地,盆地的形成演化和区域岩石圈深部具有明显多阶段或多世代沉降更替、演变迁移特点。紫金山岩体具有富碱、较富铁、贫镁、钙,SiO2不饱和,属碱性-过碱性系列;稀土元素含量高,无负铕异常;碱性岩微量元素构造环境判别属于大陆板内拉张区;岩浆活动有多期性;锶(87Sr/86Sr)、钕(143Nd/144Nd)同位素比值落入EMⅠ型地幔,岩浆物质来源较深;单颗粒锆石SHRIMP测年数据表明岩浆活动主期在125～132Ma间,为早白垩世。侏罗纪-白垩纪盆地东部及周缘存在着丰富的深部岩浆活动-热力作用,并发生了岩浆侵入或喷发活动。中生代深部背景是处于吕梁软流圈上涌区,在吕梁软流圈上涌柱软块区与西侧厚硬块区相间的上涌热浮物质聚集处,岩石圈破裂,造成盆地东部出现软流圈热浮物质底侵和岩石圈局部减薄,底侵物质再熔融上侵,形成了紫金山幔源岩浆侵入和火山喷发构成的碱性复式岩体,代表鄂尔多斯盆地与华北陆块在早白垩世经受过一期重要的热力构造事件,它是该盆地东部吕梁软流圈上涌、盆地东翼大面积抬升隆起、断隆带翘倾的表现,此与盆地构造动力体制转换期及岩浆活动-热事件对应。中生代是该盆地油气煤铀等多种能源矿产形成的重要时期。构造过程是:古生代属于大鄂尔多斯盆地,与华北地区一同�In the study of tectonic kinetics of basins,thermal process and thermal structure are the weakness and difficulty. In recent years,according to the influencing depth of magma-thermal action,there are five types of thermal tectonic units：（ancient） geothermal anomaly gathered fault zone,volcanic hydrothermal active zone（volcanic eruption of shallow layer-hydrothermal action-hypabyssal porphyry intrusion）,thermal dome,intermediate-deep intrusion （including intercrustal thermal anomaly plume） and mantle thermal plume. The Ordos basin is not only one of the basin in which oilfields were found earliest,it is also the second biggest petroliferous basin. It is located in the middle-west of the north China block,which is in the binding domain of east and west tectonic regions influenced by multistage repeated extensions and compressions,and it is a composite craton basin formed by overlapping of multi-stage and multi-system structures on the basis of the original Ordos basin,belongs to interior intracraton basin. In the eastern Ordos basin,more attention was paid in the past to study earthquake and magma activity on the basin margin such as the Fen （river） -Wei （river） rift in the southeast margin part of the basin. In the eastern part of the basin,west part of the Shanxi flexural fold belt is a large monocline stratum,which is sloping from east to west. There are a series of open and flat meridional,latitudinal extending sub-folds and a nearly east-westward fracture named the Wubu Fracture （F1） which developed well. In the east of study area,there is a fracture named the Lishi Fracture （F2） in south and north direction. Most folds and fractures belong to semi concealed style. Along with the study of tectonic background,mineralization and petroleum accumulation in the basin,we have recognized that there exists point type of thermal process from deep sourced magma in the eastern basin and its periphery. By field investigation,sample analysis,SHRIMP age determination and implication for mag

关 键 词：盆地动力学 热力作用 岩浆活动 构造热事件 深部作用 鄂尔多斯盆地 紫金山岩体 

分 类 号：P542[天文地球—构造地质学] P313[天文地球—地质学]