Details

Autor(en) / Beteiligte

• YU Lu SUN Fengyue LI Bile LI Liang LI Ruihua JIANG Hefang WANG Fei SHAO Ji SHEN Dali

Titel

Zircon U-Pb geochronology and geochemistry of syenogranitesin western Niubiziliang, northwestern Qaidam, Qinghai

Ist Teil von

• 世界地质：英文版, 2017, Vol.20 (2), p.69-79

Erscheinungsjahr

2017

Link zum Volltext

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• The study presents the results of U-Pb dating of zircons and whole-rock geochemical analyses of a syenogranite located in the western Niubiziliang area, China with the aim of determining its formation time, petrogenesis and the regional tectonic setting. Zircons within the syenogranite are euhedral-subhedral and display rhythmic growth zoning, indicating a magmatic origin. Zircon U-Pb data obtained by LA-ICP-MS indicate the syenogranite formed in the Late Permian （260. 7 ± 1. 5 Ma）. The （ SiO2 ） of syenogranites is 70. 82%- 73.59% , w ;（A1203） is 13.49%-14. 82% , and w;（Na2O ± K20） is 7. 85%-8. 52% , and yield K20/Na20 ratios of 1×10^-. Therefore, the syenogranites belong to the high-K calc-alkaline and metaluminous （ A/ CNK 〈 1 , A/NK 〉 1） series which display I-type granites similarly. The syenogranites also show the geochemi-cal characteristics of volcanic arc rocks, being enriched in large-ion lithophile elements （LILEs; K, Rb） and light rare-earth elements （LREEs; La, Ce, Sm, Nd） , but depleted in high field strength elements （HFSEs; Ta, Nb, P, Ti）. On the whole, trace element ratios are close to the mean of the Earths crust, indicating a lower-crust magma source. The low Sr （161-214） × 10^-6 and Yb （1.08-1. 80） × 10^-6 concentrations indi-cate that plagioclase and hornblende are residual mineral phases in the source. The regional geology and wholerock geochemistry suggest that the formation of the syenogranites was related to subduction of the Zongwulong Ocean crust, and the north margin of Qaidam Block during the Late Permian was in an active continental margin tectonic setting.