Geochronology, Geochemistry, and Sr-Nd-Hf Isotopes of the Diorite Porphyrites from the Weining Beishan Area, Ningxia Hui Autonomous Region: Constraints on Their Source and Tectonic Implications
Anlu Liu, Lianfu Hai, Jinke Liu, Xiaojun Zhang, Haifeng Li, Fengshun Zhao, Guoliang Zhao, Jinhe Bai
Geochronology, Geochemistry, and Sr-Nd-Hf Isotopes of the Diorite Porphyrites from the Weining Beishan Area, Ningxia Hui Autonomous Region: Constraints on Their Source and Tectonic Implications
The Weining Beishan area of Ningxia Hui Autonomous Region is located at on the western edge of the Helanshan tectonic belt, which is a tectonic joint among Alxa Block, Ordos Block, and North Qilian orogenic belt. However, the tectonic evolution of this area remains unclear due to the lack of magmatic information. This paper conducted researches on geochronology, geochemistry, and Sr-Nd-Hf isotopes of the diorite porphyrites exposed in the Weining Beishan area. The zircon U-Pb dating yields two ages of 145.0 ± 1.1 and 146.2 ± 1.5 Ma, and the whole-rock geochemical data indicate that the diorite porphyrites are metaluminous to weakly peraluminous and high-K calc-alkaline series. The characteristics of highly initial 87Sr/86Sr ratios (0.708 16 to 0.710 47), negative ε Nd(t) (−8.9 to −8.4), and negative ε Hf(t) (−13.8 to −21.2) indicate that the diorite porphyrites originated from partial melting of the middle-lower ancient crust related to the North China Craton. Combined with the regional geology, we suggested that partial melting was triggered by a tectonic activity of deep faults cutting through the crust under the regional stress transformation from compressing to extension during the Late Jurassic–Early Cretaceous, which is probably related to the westward subduction of the Paleo-Pacific Plate.
zircon U-Pb dating / Sr-Nd-Hf isotopes / magma source / diorite porphyrite / Weining Beishan area / Ningxia Hui Autonomous Region / geochronology / geochemistry
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Ningxia Institute of Geological Survey. . Regional Geology of Ningxia Hui Autonomous Regiona, 2013 Yinchuan Ningxia Institute of Geological Survey (in Chinese with English Abstract)
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