安徽沿江地区中生代碰撞后到造山后岩浆活动和壳幔相互作用——来自火山-侵入杂岩和岩石包体的证据  

Mesozoic post-collisional to postorogenic magmatic activities and crustal interaction with mantle along the Yangtze River,Anhui province:Evidence from volcanic-intrusive complexes and xenoliths

作　　者：杜杨松[1] 曹毅[1] 袁万明[1] 楼亚儿[1] 李顺庭[1] 鲁鑫[1] 

机构地区：[1]中国地质大学地质过程与矿产资源国家重点实验室,北京100083

出　　处：《岩石学报》2007年第6期1294-1302,共9页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(40672045;40272034)资助.

摘　　要：安徽沿江地区地处长江深大断裂带的中部,构造上隶属由华北板块与扬子板块在 T_2—J_2发生陆-陆碰撞形成的大别造山带的前陆带。在 J_3—K_1时期,区内发生了岩石圈伸展减薄背景下的碰撞后到岩石圈拆沉背景下的造山后岩浆活动和相应的壳幔相互作用,形成了广泛分布的碰撞后到造山后火山-侵入杂岩组合。碰撞后岩浆活动大致发生在125～145Ma,铜陵地区辉长岩包体和大量堆积岩的形成标志着这一时期的开始,而富碱岩浆岩的形成标志着这一时期的结束。在这一时期形成的岩石中,繁昌盆地中的中分村组和赤砂组火山岩以及南部侵入岩属于碰撞后岩浆岩组合中的过铝质的长英质岩套;由中部铜陵地区的中酸性侵入岩和北外带侵入岩等构成的中钾-高钾钙碱性岩系和由铜陵地区的中基性侵入岩、庐枞盆地龙门院组和砖桥组火山岩、宁芜盆地龙王山组和大王山组火山岩以及沿长江两岸呈 NE 方向分布的富碱岩浆岩构成的橄榄安粗岩系属于碰撞后岩浆岩组合中的准铝质的镁铁质-长英质火成岩岩套。造山后岩浆作用大致发生在105～125Ma。宁芜地区辉长岩的侵入标志着这一时期的开始,而宁芜和庐枞地区过碱性岩的形成标志着这一时期的结束。在这一时期形成的岩石中,由繁昌盆地蝌蚪山组火山岩和庐枞盆地双庙组火山岩以及宁芜盆地辉长岩侵入体组成的碱性岩系和由庐枞盆地浮山组火山岩和宁芜盆地娘娘山组火山岩组成的过碱性岩系属于造山后碱性-过碱性火成岩岩套。与碰撞后到造山后岩浆活动相对应,在安徽沿江地区中生代发生了两期壳幔相互作用。其中早期壳幔相互作用表现为起源于岩石圈地幔上部圈层的底侵玄武岩浆与中下地壳间强烈的相互作用,而晚期壳幔相互作用表现为起源于岩石圈地幔下部圈层的玄武岩浆与中下地壳间微弱的相互作用。The costal area of the Yangtze River in Anhui Province situated in the middle segment of the Yangtze River Deep Fault Belt is structurally located in the foreland of the Dabie Orogenic Belt. In this area are widely exposed a set of post-collisional to postorogenic associations of volcanic-intrusive complexes formed by two episodes of magmatic activities in the post-collisional to postorogenic regimes and corresponding crustal interaction with mantle occurring in the Late Jurassic to Early Cretaceous. The postcollisional magmatic activity took place in the setting of lithospheric extension and thinning at about 125 - 145 Ma. Its beginning and end are remarked by formation of gabbroic xenoliths and pyroxene cumulates in intrusions in Tongling and alkalis-rich magmatic rocks along either bank of the Yangtze River, respectively. The association formed in this episode includes peraluminous silicic rocks and metaluminous mafic-felsic igneous suites, ranging from medium- to high-K calc-alkaline to shoshonitic. The peraluminous silicic rocks include volcanic rocks of the Zhongfencun and Chisha Formations in the Fanchang Basin （FB） and intrusions distributed from Guichi to Xuanzhou. The medium- to high-K calc-alkaline suite consists mainly of intermediate-acidic intrusive rocks in Tongling and those distributed from Chuxian to Shaxi, and the shoshonitic suite is composed of intermediate-basic intrusions in Tongling, alkalis-rich magmatic rocks distributed along either bank of the Yangtze River and volcanic rocks of the Longmenyuan and Zhuanqiao Formations in the Lujiang-Zongyang Basin （ LZB ） and the Longwangshan and Dawangshan Formations in the Nanjing-Wuhu Basin （NWB）. The postorogenic magmatic activity occurred in the background of lithospheric delamination at about 105 - 125 Ma. Its beginning and end are remarked by formation of gabbro with spinel lherzolite xenoliths in NWB and phonolite with feldspathoid phenocrysts in NWB and LZB, respectively. The association formed in this episode ranges from alkaline

关 键 词：碰撞后到造山后岩浆作用 壳幔相互作用 火山-侵入杂岩 中生代 安徽沿江地区 

分 类 号：P542.5[天文地球—构造地质学] P588.14[天文地球—地质学]