长江中下游铜陵矿集区深部地壳结构:来自宽频地震P波接收函数成像的证据
投稿时间:2023-10-28  修订日期:2023-11-21  点此下载全文
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作者单位邮编
赵荣涛* 中国地质科学院 100037
刘沙沙 安徽省地质矿产勘查局321地质队 
杨艳 中国地质科学院 
黄什 安徽省地质矿产勘查局321地质队 
郑凯 安徽省地质矿产勘查局321地质队 
史大年 中国地质科学院 
中文摘要:摘要:铜陵矿集区位于长江中下游成矿带中部,自中生代以来经历来了大规模构造变形和岩浆活动。矿集区地壳深部岩石圈结构对于认识华南-华北板块的碰撞过程,以及长江中下游成矿带乃至整个华南中生代成矿的动力学过程都具有重要意义。本文利用26个宽频地震台站记录的49个远震事件,通过P波接收函数成像方法研究了长江中下游成矿带铜陵矿集区下的地壳结构。结果显示,地壳浅部存在一个深度约为3km的速度不连续界面,可能是浅部盖层与基底之间的分界面。在铜陵南部的蛤蟆岭地区,该界面向永村桥背斜两翼有加深趋势。铜陵及周边地区Moho面深度约为29~32km,横向略有变化,地壳平均纵横波速比约为1.79,相对较高,说明该地区地壳基性成分较高。该区较薄的地壳厚度和较高的波速比,表明铜陵地区经历过地壳减薄和底侵过程。我们结果显示中生代期间长江中下游地区中生代的大规模岩浆作用可能与上地幔物质上涌并底侵到下地壳的过程有关。
中文关键词:铜陵矿集区,地壳结构,P波接收函数,波速比,底侵作用
 
Deep Crustal Structure of the Tongling Ore Concentration Area in the Middle-Lower Reaches of the Yangtze River: Evidence from Broadband Seismic P-wave Receiver Functions
Abstract:Abstract: The Tongling Ore Concentration Area, located in the central part of the mineralisation belt in the middle and lower reaches of the Yangtze River, experienced large-scale tectonic deformation and magmatic activities since the Mesozoic. Its crustal structure is of great significance in understanding of the collision process of the South-North China blocks, as well as to the dynamics of Mesozoic mineralisation in the middle and lower reaches of the Yangtze River and the whole of South China. In this paper, the crustal structure of the Tongling ore concentrated area in the middle and lower reaches of the Yangtze River is investigated by P-wave receiver function imaging using 49 teleseismic events recorded at 26 broadband seismic stations. The results show that a velocity discontinuity with a depth of about 3 km exists in the shallow part of the crust, which may be the interface between basement and overlying strata. In Hamaling area in the southern Tongling, it deepens to ~5km towards the two flanks of the Yongcunqiao Anticline. The Moho depths in Tongling and its surrounding areas are about 29~32 km, with a little lateral variations. The average Vp/Vs ratio is about 1.79, which is relatively higher than normal and suggests a more mafic crust in the region. The thinner crustal thickness and higher wave velocity ratio in the region indicate that the Tongling area may have experienced a crustal thinning and a basaltic underplating. Our results suggest that the large-scale magmatism in the middle and lower reaches of the Yangtze River during the Mesozoic is likely associated with a magmatic emplacement at the base of the crust in Tongling.
keywords:Tongling ore concentration area, Crust structure, P-wave receiver function, Velocity ratio, Underplating
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