内部结构的研究被进行从 Batamayineishan 形成调查 U-Pb 年龄,踪迹元素和玄武岩的锆石的 Hf 同位素。暗岩从练习井圣罐头被获得 1 在 Junggar 盆以内在东方 Luliang 上高举。跟踪所有样品是 magmatic 的锆石表演的元素数据,与类似的 REE 模式,包括积极 Ce (Ce=5.06134 ) ,而是否定 Eu (Eu=0.06 ? 0.55 ) 在重稀土元素元素的异例和丰富。在 25 谷物之中,一致年龄被细分进三个组;300.4 整潲祺潧整的年龄?
An internal structural study was conducted to investigate U-Pb age, trace elements and Hf isotopes of basaltic zircons from the Batamayineishan Formation. The basalt was obtained from drill well San-Can 1 on the eastern Luliang uplift within the Junggar Basin. Trace element data of zircons show that all samples are magmatic, with similar REE patterns, including positive Ce (δCe=5.06-134), but negative Eu (δEu=0.06-0.55) anomalies and enrichment in heavy rare earth elements. Among 25 grains, the concordant ages were subdivided into three groups; ages of 300.4±1.3 Ma (n=11), 339.2±2.7 Ma (n=3) and 392.0±1.7 Ma (n=8). Three remaining grains were nearly concordant, with ^206pb/^238U ages of 510±7, 488±6 and 453±6 Ma, respectively. The youngest concordant age (i.e., 300.4±1.3 Ma) could be interpreted as the formation age of the studied basaltic rock; this is consistent with the sampling position at the upper part of the Batamayineishan Formation. On the other hand, ages such as Ordovician and early Devonian are consistent with the ages of island-arc volcanic rocks (enrichment in Pb) or ophiolites around the basin. Moreover, the positive εHf(t) values of the early and middle Paleozoic zircons (+3.6-+10.5) may suggest that the basement traversed by the studied volcanic rocks may be Paleozoic in age, formed from the residual oceanic crust and island-arc complex. The εHf(t) values (44.2-+17.1) of the late Paleozoic (-300.4 Ma) zircons suggest that the basaltic magmas were derived from partial melting of the asthenospheric mantle or depleted lithospheric mantle. These magmas were slightly contaminated by the existence of early-middle Paleozoic materials. The late Carboniferous basalts represent direct eruption of mantle-derived magmas at the upper crustal level during a post-collisional tectonic setting. We therefore consider that extensive vertical growth of the continental crust to have occurred before the late Carboniferous.