Abstract:
The Longjiang Formation in northern Da Hinggan Mountains is composed mainly of dacite and rhyolite with minor andesite. the LA-ICP-MS zircon U-Pb dating of these rocks yielded ages of 122.2~126.5Ma, corresponding to Early Cretaceous. These volcanic rocks are of high potassium calc-alkaline series possessing such geochemical characteristics as high ΣREE, remarkable (La/Yb)N values and negative Eu anomalies. In the spidergram, the rocks show pronounced enrichment of Rb, Ba, Th, U, K and depletion of Nb, Ta, P, Ti, much identical with the characteristics of the upper crust. Most of these rocks have typical adakitic characteristics, as shown by the data 300
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