Crustal contamination and magmatic evolution of the Bijiashan basic–ultrabasic intrusion belt in the Beishan Terrane, northeastern Tarim Craton (NW China). (26th April 2018)

• Record Type: Journal Article
• Authors: Xia, Zhaode; Du, Wei; Xia, Mingzhe; Jiang, Changyi
• Editors: Yang, G.
• Other Names: Li S. guestEditor.; Suo Y. guestEditor.; Li R. guestEditor.; Yu S. guestEditor.; Yang G. guestEditor.; Somerville I. guestEditor.
• Is Part Of: Geological journal. Volume 53(2018)Supplement 2
• Page Start: 30
• Page End: 43
• Publication Date: 2018-04-26
• Subjects: basic–ultrabasic rocks -- crustal contamination -- magma source -- magmatic evolution -- parental magma; Geology -- Periodicals; 551
• DOI: 10.1002/gj.3219
• Languages: English
• ISSNs: 0072-1050

Abstract

Abstract : The Bijiashan intrusion belt, one of the basic–ultrabasic intrusion belts in the Beishan Terrane, northeastern Tarim Craton, is composed of the Hongshishan, Hongshishanxi, Xuanwoling, Bijiashandong, and Bijiashan intrusions. These intrusions are mainly composed of dunite, troctolite, olivine gabbro, and gabbro. Magma evolution of the intrusions was strongly controlled by fractional crystallization, and the crystallization sequence was mainly olivine → plagioclase → pyroxene. This is evidenced by whole‐rock MgO contents that are positively correlated with TFe2 O3 and negatively correlated with Al2 O3, CaO, and Na2 O and an increase in total rare‐earth element and trace elements contents from ultrabasic to basic rocks. Most of the basic–ultrabasic rocks are enriched in large ion lithophile elements (Cs, Rb, Sr, and U) and depleted of high field strength elements (Zr, Hf, Nb, Ta, and Ti). The variable and relatively low Ce/Pb (0.17–7.3) and Nb/U (0.13–10.1) ratios, variable Th/Yb (0.02–4.1) ratio, initial 87 Sr/ 86 Sr ratios (0.7033 to 0.7094) and ε Nd (t) (7.54 to −4.25), suggest less than 6% crustal contamination. Based on the maximum Fo value of olivine (Fo90), whole‐rock average composition and olivine–liquid compositional relationships, the parental magma is of high‐Mg basaltic magma containing 13.4 wt.% MgO. According to rare‐earth element contents and Sr–Nd isotopic compositions, the parental magma was originated from partial melting of depleted sub‐continental lithospheric mantle.