Implications for the lithospheric structure of Cambay rift zone, western India: Inferences from a magnetotelluric study
Implications for the lithospheric structure of Cambay rift zone, western India: Inferences from a magnetotelluric study
复制标题
DOI：
10.1016/j.gsf.2020.01.014
复制
发表时间：
2020-02
影响因子：
8.9
通讯作者：
Nagarjuna Danda;C.K. Rao;Amit Kumar;P. Rama Rao;P.B.V. Subba Rao
中科院分区：
文献类型：
--
作者：
Nagarjuna Danda;C.K. Rao;Amit Kumar;P. Rama Rao;P.B.V. Subba Rao
宽频带和长周期的大地电磁（MT）数据采集沿着东西走向的导线近200公里的Kachchh，Cambay裂谷盆地，Aravalli-Delhi褶皱带（ADFB），印度西部。大地电磁测深资料的区域走向分析表明，该导线下的地电走向大致为N59°E，与研究区的主要地质走向基本一致。分解的横电（TE）和横磁（TM）的数据模式进行了反演，使用非线性共轭梯度算法的图像电气岩石圈结构的Cambay裂谷盆地及其周边地区。这些研究表明，在Kachchh和Cambay裂谷盆地下面有一层厚（约1-5公里）的导电第三纪-中生代沉积物。电阻块体表明存在基性/超基性火山侵入岩、亏损地幔岩石圈和不同的前寒武纪构造单元。ADFB中描绘的地壳导体表明断层带内存在流体，多相变质岩内存在硫化物矿化，和/或Aravalli-Delhi沉积物/变质沉积物。所观察到的导电异常的Cambay裂谷盆地下表明存在玄武岩底侵，挥发性（CO2，H2O）富集熔体和通道化的熔体馏分/流体到地壳深处发生的地幔柱-岩石圈相互作用。电阻率在剖面上的变化表明，留尼汪地幔柱对Cambay裂谷盆地岩石圈结构的影响在印度西部大陆边缘（WCMI）更为显著，从而支持了坎贝尔和Griffiths关于地幔柱-岩石圈相互作用的假说。
Broad-band and long-period magnetotelluric (MT) data were acquired along an east-west trending traverse of nearly 200 km across the Kachchh, Cambay rift basins, and Aravalli-Delhi fold belt (ADFB), western India. The regional strike analysis of MT data indicated an approximate N59°E geoelectric strike direction under the traverse and it is in fair agreement with the predominant geological strike in the study area. The decomposed transverse electric (TE)- and transverse magnetic (TM)-data modes were inverted using a nonlinear conjugate gradient algorithm to image the electrical lithospheric structure across the Cambay rift basin and its surrounding regions. These studies show a thick (~1–5 km) layer of conductive Tertiary–Mesozoic sediments beneath the Kachchh and Cambay rift basins. The resistive blocks indicate presence of basic/ultrabasic volcanic intrusives, depleted mantle lithosphere, and different Precambrian structural units. The crustal conductor delineated within the ADFB indicates the presence of fluids within the fault zones, sulfide mineralization within polyphase metamorphic rocks, and/or Aravalli-Delhi sediments/metasediments. The observed conductive anomalies beneath the Cambay rift basin indicate the presence of basaltic underplating, volatile (CO2, H2O) enriched melts and channelization of melt fractions/fluids into crustal depths that occurred due to plume–lithosphere interactions. The variations in electrical resistivity observed across the profile indicate that the impact of Reunion plume on lithospheric structures of the Cambay rift basin is more dominant at western continental margin of India (WCMI) and thus support the hypothesis proposed by Campbell & Griffiths about the plume–lithosphere interactions.