Petrogenesis and ore genesis of the ilmenite-rich Kendelong mafic-ultramafic intrusion in Wulan, Qinghai

作者：Kang Zhen^*; Jiang ChangYi; Ling JinLan; Zhao YanFeng; Song YanFang; Zhou Wei

来源：Acta Petrologica Sinica, 2015, 31(8): 2193-2210.

• Mafic-ultramafic intrusions
• Llmenite enrichment
• Zircon U-Pb age
• Juvenile lithospheric mantle
• The northern margin of the Qaidam basin

The Kendelong mafic-ultramafic intrusion is located at the Olongbuluke micro-continent, which is in the northern margin of the Qaidam basin, Qinghai Province. The rock types of this fragmentarily outcropped intrusion widely range from serpentinite, clinoperidotite, iherzolite, olivine websterite, olivine clinopyroxenite, olivine gabbro, olivine-bojite, bojite, alterated gabbro to anorthosite. Scatteredly and speckledly disseminated ilmenite ore exists in the pyroxenolite and gabbro. The content of the ilmenite is 5% similar to 10%, in some samples it can achieve 10% similar to 20%. Enrichment of ilmenite happened at the late stage of magma evolution. The zircon U-Pb age of the gabbro from the intrusion is 491 +/- 3Ma (MSWD = O. 7). According to the geochemical compositions, the intrusion has a tholeiitic affinity. The REE patterns of all rocks have the same characteristics, namely the right slope with LREE enrichment. The complex is characterized by enrichment of LILEs (Cs, Rb, Ba, Th, U) and depletion of HFSEs (Nb, Ta, Ti, P). (Sr-87/Sr-86), values vary from 0. 704731 to 0. 710280, epsilon(Nd) (t) values are between -4. 49 and +0. 83. Fractional crystallization of olivine, orthopyroxene, clinopyxene, plagioclase takes place in magma condensation process, and crustal contamination is significant from the evidence of petrochemistry. The primary magma of the Kendelong intrusion is basaltic, which origined from a juvenile lithospheric mantle that was previously metasomatized by subduction zone fluids /melts in the Paleozoic. It may be the highly differentiated magma that achieved the enrichment of the iron titanium oxide. It lead to the formation of the ilmenite deposit in the condition of f(02) < NNO.

• 出版日期2015-8
• 单位中国科学院大学; 中国科学院地质与地球物理研究所; 中国科学院地质与地球物理研究所兰州油气资源研究中心; 长安大学