Ages, geochemistry and tectonic implications of the Cambrian igneous rocks in the northern Great Xing'an Range, NE China. (15th August 2017)

• Record Type: Journal Article
• Authors: Feng, Zhiqiang; Liu, Yongjiang; Li, Yanrong; Li, Weimin; Wen, Quanbo; Liu, Binqiang; Zhou, Jianping; Zhao, Yingli
• Is Part Of: Journal of Asian earth sciences. Volume 144(2017)
• Page Start: 5
• Page End: 21
• Publication Date: 2017-08-15
• Subjects: Great Xing'an Range -- Early Paleozoic -- Igneous rocks -- Sr–Nd–Hf isotopes -- Xinlin–Xiguitu suture zone -- Central Asian Orogenic Belt; Earth sciences -- Asia -- Periodicals; Sciences de la terre -- Asie -- Périodiques; Earth sciences; Asia; Periodicals; 555.05
• DOI: 10.1016/j.jseaes.2016.12.006
• Languages: English
• ISSNs: 1367-9120

Abstract

Graphical abstract: Highlights: The Xinglong granitoids were derived from the partial melting of a dominantly Paleo-Mesoproterozoic "old" crustal source with possible different degrees of addition of juvenile materials. The ca. 480 Ma Xinglong granitoid rocks possess the geochemical characteristics of post-collision granite affinity, whereas the similar-aged rhyolitic tuffs and ultramafic intrusion from the Duobaoshan Formation show the geochemical characteristics of island-arc igneous rock and occurred in an island-arc tectonic setting. Abstract: The Xinlin–Xiguitu suture zone, located in the Great Xing'an Range, NE China, in the eastern segment of the Central Asian Orogenic Belt (CAOB), represents the boundary between the Erguna and Xing'an micro-continental blocks. The exact location of the Xinlin-Xiguitu suture zone has been debated, especially, the location of the northern extension of the suture zone. In this study, based on a detailed field, geochemical, geochronological and Sr–Nd–Hf isotope study, we focus our work on the Cambrian igneous rocks in the Erguna-Xing'an block. The Xinglong granitoids, mainly include ∼520 Ma diorite, ∼470 Ma monzogranite and ∼480 Ma pyroxene diorite. The granitoids show medium to high-K calc-alkaline series characteristics with post-collision granite affinity. The circa 500 Ma granitoids have low εHf ( t ) values (−16.6 to +2.2) and ancient two-stage model ( T DM2 ) ages between 1317 Ma and 2528 Ma. These results indicate the primary magmas of the Xinglong granitoids were probably derived from the partial melting of a dominantly Paleo-Mesoproterozoic "old" crustal source with possible different degrees of addition of juvenile materials, and formed in a post-collision tectonic setting after the amalgamation of the Erguna and Xing'an blocks. Compared with the Xinglong granitoids, the Duobaoshan igneous rocks are consisted of the approximately coeval rhyolitic tuffs (491 ± 5 Ma) and ultramafic intrusions (497 ± 5 Ma) within the Duobaoshan Formation. They are generally enriched in large ion lithophile elements (LILEs) and depleted in high field strength elements (HFSEs; e.g., Nb, Ta, and Ti), consistent with the geochemistry of igneous rocks from island arcs or active continental margins. The ultramafic rocks have high positive εHf ( t ) values (+1.3 to +15) and εNd ( t ) (+1.86 to +2.28), and relatively young two-stage model ( T DM2 ) ages and low initial 87 Sr/ 86 Sr ratios (0.70628–0.70853), indicating the partial melting of a depleted mantle source from a subducted slab in the ocean basin between the Erguna-Xing'an and Songliao blocks. The rhyolitic tuffs contain a group of Phanerozoic zircons with εHf ( t ) values (−4.6 to +15.0), suggesting that the rhyolitic tuffs were derived from juvenile lower crustal material with some ancient crustal material. Coupled with our previous geochemical and isotopic studies on Early Paleozoic igneous rocks, we proposed that the collision of the Erguna and Xing'an blocks at least took place ca. 500 Ma ago, and that there exist in a westward subduction of an oceanic plate between the Eruguna-Xing'an and Songliao blocks, took place during the Early Ordovician. Up to now, there are more evidences and constraints that the northern extension location of the Xinlin-Xiguitu suture zone is located in the Jifeng–Xinglong areas.