Geochemical Characteristics of Bayinzhurihe Pluton and Its Tectonic Significance, Bayan Obo, Inner Mongolia
详细信息
- 责任者：Luo Hongling (The Key Laboratory of Orogenic Belts and Crustal Evolution ; Ministry of Education ; Beijing 100871 ; China) ; Wu Tairan
- 刊名：Geological Journal of China Universities
- 出版年：2013
- 卷期：19(1)
- 页码：p.123-132
- issnNo：ISSN1006-7493
- isbnNo：CN32-1440/P
摘要
The middle segment of northern margin of the North China Plate was influenced by intense tectonic and magmatic activity during the Permian.Dozens of intrusions formed an E-W trending magmatic belt that extended from the Dongshenmiao to Xianghuang Qi,Inner Mongolia,with a length of 400 km and width of 30 km.As a representative,Bayinzhurihe Pluton consists of quartz diorite and hornblende gabbro,which belong to high-potassium calc-alkaline series.They are characterized by low SiO 2(49.72%～59.34%) and high Al 2 O 3(15.79%～19.50%) contents,with Mg # =38～44,enrichment in large ion lithophile elements(LILE,e.g.,Ba=829×10-6 ～1104×10-6,Sr=502×10-6 ～726×10-6),relative depletion in high field strength elements(HFSE,e.g.,Nb,Ta) in primitive mantle-normalized spidergrams,and right-inclined rare earth element patterns,mostly with slightly negative Eu anomalies(δEu=0.63～1.09).Their low Sr/Nd ratios(12～24) and La/Nb ratios(1.33～2.39) may reflect intraplate magmatism involved.Hornblende gabbro shows non-arc-like(Nb/Th =9.6-18.4) basalt affinity compositions.LA-ICP-MS U-Pb zircon dating of the Pluton yielded an intrusive age of 265±2Ma.Its zircons have ε Hf(t)=-13.0～-17.2 andt DM C =2.12～2.38 Ga,mainly show the characteristics of lower continental crust.These features lead us to conclude that Bayinzhurihe Pluton was generated by mixing of lower crustal-derived mafic melt and minor enriched mantle-derived mafic magma,followed by fractional crystallization,due to crustal extension in post-collisional setting.