學術資源整合系統-相關推薦

 
作者Kuo-An Tung*, Houng-Yi Yang, Dun-Yi Liu, Jian-Xin Zhang, Huai-Jen Yang, Yen-Hong Shau, Chien-Yuan Tseng
出版日期2013
著作名稱The Neoproterozoic granitoids from the Qilian block, NW China:Evidence for a link between the Qilian and South China blocks
235: 163-189 (SCI)
摘要tThe field occurrence, petrography, geochemistry, Sm–Nd isotopes, and geochronology of the Neopro-terozoic granitoids exposed at Tuole, Huangyuan, Gahai, Haiyan, Riyueshan, Baokuhe, and Maxianshanin the Qilian block were studied. The Neoproterozoic granitoids in the Qilian block form two age groups:ca. 800 Ma and ca. 900 Ma. The ca. 800 Ma group granitoids consist of granodiorite and granite, whereasthe ca. 900 Ma group granitoids quartz diorite, granodiorite, and potassic granite. They have intrudedthe Huangyuan Group in the basement sequence of the Qilian block. The foliations are moderately towell-developed and are concordant with those of the country rocks. The granitoids of both age groups allshow enrichment in LREEs, but this enrichment is more pronounced in the ca. 800 Ma group than in theca. 900 Ma group. All granitoids show negative europium anomalies, but the ca. 800 Ma group granitoidsare more varied in Eu/Eu* values (0.23–0.83) than most of the ca. 900 Ma group granitoids (0.54–0.98).Spider diagrams of both groups also exhibit enrichment in large ion lithophile elements, i.e., Rb, Th, U,and K, and negative anomalies in Nb–Ta, Sr, P, Ti, and, with exception of the Maxianshan quartz diorite,Ba. The εNd(1 Ga) and TDMare −6.7 to −12.7 and 2.2–3.0 Ga for the ca. 800 Ma granitoids and are −4.3 to−5.2 and 2.0–2.3 Ga for the ca. 900 Ma granitoids. The granitoids of the ca. 900 Ma group are interpretedto have formed in an arc tectonomagmatic environment on an active continental margin, whereas thoseof the ca. 800 Ma group are thought to form in a continental rift environment. The ca. 900 Ma granitoidsare I-type and could be formed from partial melting of K-rich metabasalt or eclogite with significantamount of mantle components at a pressure of 1–4 GPa in the lower crust. The strongly peraluminous orperaluminous Gahai granites and Haiyan granodiorite are S-type and could be derived from melting ofclay-poor, mature psammitic sources.Similarities in age and tectonic environment of magma genesis suggest a correlation of Neoproterozoicgranitoid magmatism between the Qilian and South China block. This correlation gives a strong supportto the consideration that the two blocks might be unified in the Neoproterozoic. In other words, the Qilianblock might be a part of the South China block or, more precisely, the Sibao orogen, in the Neoproterozoictime.
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