摘要
钦杭成矿带和武夷山成矿带是华南大陆两个重要的成矿带,成矿作用主要发生于中生代陆内造山时期.地质研究表明,基底和地表断裂的特征对成矿过程有重要的控制作用,研究上地壳结构特征对成矿差异性特征的认识有重要的参考价值.为此,本文基于跨越钦杭、武夷山成矿带江西万载至福建惠安的NW-SE向深地震测深剖面初至波数据,利用有限差分走时反演方法,获得了钦杭、武夷山成矿带8 km深度范围内的上地壳P波速度结构,其主要特征为:(1)钦杭、武夷山成矿带上地壳P波速度横向非均匀特征明显,以5.8 km·s^-1速度等值线作为基底参考面,发现剖面基底埋深较浅,约1.0~3.0 km;钦杭成矿带的基底埋深总体小于武夷山成矿带,分别为0.5~2.0 km和1.5~3.0 km;(2)P波高速区(速度正异常区)与地表出露的岩浆岩对应较一致,P波低速区(速度负异常区)与主要的断裂位置或沉积盆地对应较一致,绍兴—江山—萍乡断裂和政和—大浦断裂下方的低速特征显示两条断裂至少向深部延伸8 km以上,暗示两条断裂具备深大断裂的性质,推测绍兴—江山—萍乡断裂可能是扬子块体和华夏块体的边界;(3)综合已有的地质、地球物理资料,我们推测钦杭成矿带和武夷山成矿带上地壳P波速度的不同,反映了深部岩浆作用过程的差异,基底深度及断裂性质是造成两个成矿带成矿差异的重要因素.
The Qinhang Metallogenic Belt(QMB)and Wuyishan Metallogenic Belt(WMB)are two major ones in South China,in which mineralization occurred mainly in an intracontinental orogeny during the Mesozoic.Geologic research shows that the characteristics of crystalline basement and faults have significant controls on the metallogenic processes,so probing the upper crustal structure has reference value to the study on the distinction of the metallogenesis.This work builds on the first arrival data from the NW-SE Deep Seismic Sounding(DSS)profile,which transects the QMB and the WMB,extending from Waizai,Jiangxi Province to Hui′an,Fujian Province.The upper crustal P wave velocity structure at depths 0~8 km is imaged by using the finite difference travel time tomography method.The results show that(1)the P wave velocity of the QMB and WMB is heterogeneous in lateral direction and the crystalline basement is relatively shallow,about 1.0~3.0 km,using the 5.8 km·s^-1 contour line as reference.The crystalline basement′s depth of the QMB is relatively smaller than the WMB,with 0.5~2.0 km and 1.5~3.0 km,respectively.(2)The high velocity zones(positive velocity anomaly)have a good accordance with the magmatic rocks on the surface,while the low velocity zones(negative velocity anomaly)have a good accordance with the major faults or the sedimentary basins.The low velocity beneath the Shaoxing-Jiangshan-Pingxiang Fault(SJPF)and Zhenghe-Dapu Fault(ZDF)indicates that both extend downward more than 8 km,which separate the Yangtze block and Cathaysia block.(3)Based on the existing geological and geophysical data,we speculate that the discrepancy of the upper crustal P wave velocity,the depth of crystalline basement and the faults′properties beneath the QMB and WMB are the key factors to result in the discrepancy of the two metallogenic belts.
作者
林吉焱
唐国彬
徐涛
蔡辉腾
吕庆田
白志明
邓阳凡
黄敏夫
金星
LIN JiYan;TANG GuoBin;XU Tao;CAI HuiTeng;Lü QingTian;BAI ZhiMing;DENG YangFan;HUANG MinFu;JIN Xing(State Key Laboratory of Lithospheric Evolution,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;Geophysical Exploration Center,China Earthquake Administration,Zhengzhou 450002,China;Earthquake Administration of Fujian Province,Fuzhou 350003,China;Chinese Academy of Geological Sciences,Beijing 100037,China;State Key Laboratory of Isotope Geochemistry,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,China;University of Chinese Academy of Science,Beijing 100049,China;CAS Center for Excellence in Tibetan Plateau Earth Sciences,Beijing 100101,China)
出处
《地球物理学报》
SCIE
EI
CAS
CSCD
北大核心
2020年第12期4396-4409,共14页
Chinese Journal of Geophysics
基金
国家重点研发计划(2016YFC0600201)
国家自然科学基金(41790461,41974048,41804060,41774097)联合资助.
关键词
钦杭成矿带
武夷山成矿带
有限差分走时反演
结晶基底
上地壳速度结构
Qinhang Metallogenic Belt(QMB)
Wuyishan Metallogenic Belt(WMB)
Finite difference traveltime inversion
Crystalline basement
Upper crustal velocity structure
