摘要
秦岭、祁连、昆仑造山带结合处的共和盆地记录了复杂的构造、岩浆、变质和沉积作用事件,是研究青藏高原北部构造-岩浆演化的关键地区。近年来,共和盆地花岗岩类高温干热岩的发现使得该区成为新型地热资源的战略基地。然而,有关干热岩原岩的组成、侵位时代、结晶温压及其时空分布等特征仍不清楚,制约着干热岩地热能勘查开采及该区构造-热演化历史的认识。本文以共和盆地东北部恰卜恰地区3口干热岩钻井岩芯和野外露头样品为基础,结合区域地质调查资料,开展了系统的岩石学、锆石U-Pb年代学和矿物温压计研究。研究发现,该区干热岩主要由花岗闪长岩、英云闪长岩、二长花岗岩和正长花岗岩等花岗岩类组成,偶见闪长岩包体。电子探针分析显示,样品中多数角闪石为铁角闪石。角闪石-斜长石矿物对温压计研究表明,岩体的结晶压力属于中低压(1.91~3.52kbar),温度为中低温(681~693℃),其岩浆结晶深度约在7.2~13.2km。锆石Ti饱和温度计分析表明,该区岩浆结晶温度主要为643~804℃,而恰卜恰北部的沟后杂岩体相较干热岩钻井岩芯钻揭的杂岩体具有更高的结晶温度。锆石U-Pb年代学分析表明,共和盆地东北部恰卜恰地区干热岩原岩形成时间主要为243~236Ma和225~210Ma两个时期,存在不同时期、不同源区的侵入,与印支期青藏高原北部古特提斯洋盆的俯冲消减相关。之后,共和干热岩经历了至少4.2km的隆升剥露。结合前人多种地球物理研究资料,构建了该区深部四层结构构造剖面,干热岩热源可能与地幔上涌、中下地壳存在局部熔融体有关,且受多条隐伏断裂的影响,盆地基底下的干热岩地热藏具有分区性。
Gonghe basin,located at the junction of Qinling,Qilian and Kunlun orogenic belts,records complex tectonic,magmatic,metamorphic and sedimentary events,and is a key area to study the tectonic and magmatic evolution of the northern Tibetan Plateau.In recent years,the discovery of high-temperature Hot Dry Rock(HDR)in Gonghe basin makes this area a strategic base of new geothermal resources.However,the composition,emplacement age,temperature,pressure,depth and spatiotemporal distribution of HDR are not clear,which restricts the exploration and exploitation of geothermal energy and the understanding of tectonic-thermal evolution history in this area.In combination with the regional geological survey data,we carried out systematic petrology,zircon U-Pb geochronology and mineral thermobarometer on three drilling cores and field outcrop samples of Qiabuqia area in the northeastern Gonghe basin.It is found that the hot dry rocks in this area are mainly composed of granodiorite,tonalite,monzonitic granite and syenite granite,with diorite enclave occasionally.The results of electron microprobe analysis show that most of the hornblendes in the samples are iron hornblende.The hornblende-plagioclase thermobarometer results show that the formation pressure of hornblende in the HDRs of the Gonghe basin belongs to medium low pressure(1.91~3.52 kbar),with medium to low temperature(681~693℃),and the crystallization depth of magma is about 7.2~13.2 km.The results reveal that the crystallization temperature of magma in Qiabuqia area of Gonghe basin is 643~804℃,while the Gouhou complex in the northern Qiabuqia has higher crystallization temperature than the drilling cores in the south.Zircon U-Pb geochronology analysis shows that the protoliths of Qiabuqia area in the northeastern Gonghe basin were mainly formed in 243~236 Ma and 225~210 Ma.There were different periods and different origins of intrusion,which was related to the subduction and closure of the Paleo-Tethys ocean basin in the northern Qinghai-Tibet Plateau during Indosinian.After that,at least 4.2 km of crust rock was exposed above HDR in the Gonghe basin.Combined the previous multiple geophysical data,the deep four-layer architectural structure profile is constructed.The heat source of HDR may be related to the upwelling of mantle and the existence of melting body in the middle and lower crust.And influenced by several hidden faults,the geothermal reservoirs of the HDR under the basement in the Gonghe basin have been partition.
作者
贠晓瑞
陈希节
蔡志慧
何碧竹
张盛生
雷敏
向华
YUN XiaoRui;CHEN XiJie;CAI ZhiHui;HE BiZhu;ZHANG ShengSheng;LEI Min;XIANG Hua(Key Laboratory of Deep-Earth Dynamics of Ministry of Natural Resources,Institute of Geology,Chinese Academy of Geological Sciences,Chinese Academy of GeologicalSciences,Beijing 100037,China;China University of Geosciences(Beijing),Beijing 100083,China;Southern Marine Science and Engineering Guangdong Laboratory,Guangzhou 511458,China;Development and Research Center of China Geological Survey,Beijing 100037,China;Qinghai Survey Institute of Hydrogeology and Engineering&Environmental Geology,Xining 810008,China)
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2020年第10期3171-3191,共21页
Acta Petrologica Sinica
基金
中国地质科学院地质研究所先导研究项目(A1903)
中国地质科学院基本科研业务项目(JYYWF20180903、J1901-11、J1901-20-4)
国家自然科学基金项目(41872121)
南方海洋科学与工程重大专项(GML2019ZD0201)
中国地质调查局项目(DD20190006、DD20190060、DD20190131)
青海省重点研发计划(2018-SF-109)联合资助。
关键词
干热岩
锆石Ti温度计
角闪石-斜长石温压计
侵位深度
岩浆结晶温度
共和盆地
Gonghe basin
Hot dry rock
Titanium-in-zircon thermometry
Hornblende-plagioclase thermobarometry
Emplacement depth
Magmatic crystallization temperature
作者简介
第一作者:贠晓瑞,男,1993年生,博士生,构造地质学专业,E-mail:yunxrgeo@163.com;通讯作者:何碧竹,女,1965年生,研究员,从事盆-山构造、古地理及油气勘探目标评价研究,E-mail:hebizhu@cags.ac.cn。