Geochemical Characteristics of Early Cretaceous Intermediate-mafic Dykes in Susong Terrene of Dabie Orogenic Belt(PDF)
《地球科学与环境学报》[ISSN:1672-6561/CN:61-1423/P]
- Issue:
- 2016年第06期
- Page:
- 835-848
- Research Field:
- 基础地质与矿产地质
- Publishing date:
Info
- Title:
- Geochemical Characteristics of Early Cretaceous Intermediate-mafic Dykes in Susong Terrene of Dabie Orogenic Belt
- Author(s):
- XIE Qing-lu; LI Shuang-qing; HE Jian-feng; CHEN Fu-kun
- 1. School of Earth and Space Sciences, University of Science and Technology of China, Hefei, 230026, Anhui, China;2. Department of Navigation, Bengbu Naval Petty Officer Academy, Bengbu 233012, Anhui, China
- Keywords:
- geochemistry; intermediate-mafic dyke; Early Cretaceous; Sr-Nd-Pb isotope; curstmantle interaction; delamination; Susong terrene; Yangtze Block; Dabie orogenic belt
- PACS:
- P588.13
- DOI:
- -
- Abstract:
- Dabie orogenic belt is a typical continental collision belt by Triassic subduction and collision between Yangtze Block and North China Block. It is characterized by not only the largest exposure of Triassic ultrahigh-pressure metamorphic rocks in the world, but also the most profound occurrence of post-collisional Cretaceous igneous rocks. Early Cretaceous intermediate-mafic dykes, intruding into high-pressure metamorphic rocks of Susong terrene of Dabie orogenic belt, are important for understanding the process of mantle-crustal interaction during the deep subduction of the continental block and the tectonic respondence in the uplift. The petrological and geochemical characteristics of these intermediate-mafic dykes were presented, and the petrogenesis and geological implications were discussed. The results show that the intermediate-mafic dykes are mainly latite in composition; they have varied compositions in major elements (e.g., mass fractions of SiO2 are 48.45%-61.37%), and basic dyke samples show relatively high mass fractions of MgO, Cr and Ni; all the dyke samples display homogeneous characteristics in trace element and rare earth element compositions, such as enrichment in large ion lithophile elements (LILE) and light rare earth elements (LREE), and obvious depletion in high field strength elements (HFSE, e.g., Nb, Zr and Ti) and heavy rare earth elements (HREE). Isotopic compositions indicate that magma sources of the intermediate-mafic dykes are relatively enriched with the characteristics of initial N(87Sr)/N(86Sr)(0.706 3-0.710 9) andεNd(t)(-22.7--15.1); the initial Pb isotopic ratios are low with N(206Pb)/N(204Pb) of 15.858 5-17.196 7, N(207Pb)/N(204Pb)of 15.207 2-15.332 1, and N(208Pb)/N(204Pb) of 36.814 4-37.633 8, indicating the contribution of lower crustal materials of Yangtze Block. In general, the Early Cretaceous intermediate-mafic dykes in Susong terrene have high Sr, low Y and Yb contents, being comparable to typical adakite, implying that the generation of these dykes would be related to the delamination of thickened orogenic lower crust and the relative interaction with upper mantle.
Last Update: 2016-12-01