|کد مقاله||سال انتشار||مقاله انگلیسی||ترجمه فارسی||تعداد کلمات|
|109287||2018||44 صفحه PDF||سفارش دهید||10018 کلمه|
Publisher : Elsevier - Science Direct (الزویر - ساینس دایرکت)
Journal : Lithos, Available online 5 April 2018
The Lajishan belt of the Central Qilian block was a back-arc basin during Early Paleozoic. The basaltic magmatism and temporal evolution in this basin provide an opportunity to study the development of back-arc basin in an active continental margin. In this study, we carry out an integrated study of geochronlogical, geochemical and Sr-Nd isotopic compositions for the Early Paleozoic arc-like and OIB-like basalts. The Lajishan arc-like basalts are enriched in large ion lithophile element (LILE) and show negative Nb and Ta anomalies whereas the OIB-like basalts have high LILE abundances and show positive Nb and Ta anomalies. The arc-like basalts have initial 87Sr/86Sr values of 0.7050â0.7054 and ÎµNd(t) values of +0.51â¯ââ¯+2.63, and the OIB-like basalts have initial 87Sr/86Sr values of 0.7049â0.7050 and ÎµNd(t) values of +0.66â¯ââ¯+1.57. The geochemical and Sr-Nd isotopic compositions suggest that the arc-like basalts are derived from partial melting of a depleted mantle source metasomatized by slab-derived components at shallow depth levels, and the OIB-like basalts also originated from a metasomatized mantle wedge source. U-Pb zircon dating yielded the ages of ~494â¯Â±â¯4â¯Ma for the arc-like basalts and ~468â¯Â±â¯6â¯Ma for the OIB-like basalts. We argue that the arc-like basalts are products of back-arc extension before the back-arc rifting initiated in earlier stage, resulting from the northward subduction of the Qaidam-West Qinling oceanic slab, while the OIB-like basalts represent products of further back-arc spreading in response to rollback of the Qaidam-West Qinling oceanic lithospheric slab. The association of arc-like and OIB-like basalts in the Lajishan belt records the development of back-arc basin from initial rifting to subsequent spreading, offering insight into how basaltic magmatism generates in the formation of back-arc basin in subduction zone setting.