- 责任者：Jin Xiaoye (State Key Laboratory of Geological Processes and Mineral Resources ; China University of Geosciences ; Wuhan 430074 ; China) ; Li Jianwei
- 刊名：Journal of Earth Sciences and Environment
- 出版年：2013
- 卷期：35(3)
- 关键词：杂岩 ; complexes ; 铀—铅计时 ; U-Pb dating ; 秦岭 ; Qinling Mountains
- 页码：p.20-38
- 图表：12 illus., 3 tables, 80 refs.
- 分类号：0801
- issnNo：ISSN1672-6561
- isbnNo：CN61-1423/P
The Dewulu intrusive complex, which is located in the west part of western Qinling orogenic belt and north of Xiahe-Hezuo fault zone, is composed of two intrusive units includingDewulu quartz diorite and Laodou quartz diorite porphyry, and Dewulu quartz diorite contains a lot of mafic microgranular enclaves. Zircon U-Pb ages, whole-rock element geochemical and Sr- Nd isotopic composition of quartz diorite, quartz diorite porphyry and mafic microgranular enclave in quartz diorite were presented in order to constrain the emplacement age and petrogenesis of Dewulu intrusive complex, and the tectonic significance was discussed. The results from LA-ICP- MS Zircon U-Pb dating show that emplacement ages of Dewulu quartz diorite and Laodou quartz diorite porphyry are （238. 6 ±1.5） Ma and （247.6 ± 1.3） Ma respectively, constraining their formation in Early-Middle Triassic magmatism. Mass fractions of SiO2 are 64.21±66.22% for quartz diorite, 56.28%-58.18% for mafic microgranular enclave and 62.33%-64.58%0 for quartz diorite porphyry, total alkali content is high, K is relatively rich and the ratio of mass fractions of Na20 and K2O is close to or more than 1. Quartz diorite and mafic microgranular enclave are metaluminous, quartz diorite porphyry is metaluminous-weak peraluminous, but they are of medium-high K calc-alkaline series and have high Mg＂ values （61-70）. Compositions of trace element and rare earth element are similar for each unit of Dewulu intrusive complex, ratio of mass fractions of La and Yb with chondrite normalized （ω（La）N/ω（Yb）N） is 6. 88-16. 55, and Eu negative anomaly is 0. 43 0. 79. Sr-Nd isotopic compositions of quartz diorite, quartz diorite porphyry and mafic microgranular enclave are similar, initial Sr isotopic ratios are 0. 707 3-0. 707 8, values of eNd（t） are --6. 7---7. 6. The geochemical and Sr-Nd isotopic compositions indicate that quartz diorite and quartz diorite porphyry may be generated by partial melting of K-rich meta- basaltic rocks in the lower crust, with the addition of mantle-derived magmas; geochemical features of mafic microgranular enclave is similar with high-Mg andesite, and the source may be an enriched lithospheric mantle derived by the metasomatism of plate fluid or melting. Combined with regional geological setting, Dewulu intrusive complex is a product of arc magmatism formed in an active continental margin setting, which is related to the northward subduction of Paleo- Tethys ocean during Early Indosinian.