Tectonic setting and geochemistry of amphibolites in the North Qaidam
柴北缘斜长角闪岩的地球化学特征及其构造背景

Amphibolites from HP/UHP metamorphic belt in the North Qaidam Mountains can be subdivided into two types. One type was resulted from retrograded eclogite, whereas another type underwent only amphibolite-facies metamorphism. Their protoliths may be tholeiites with characteristics of enriched-LREE and depleted Nd isotope. The basic magma was derived from different mantle sourse volume without obvious crust contamination, and formed in a continental rift or an incipient oceanic basin setting representing precursor of the early Paleozoic ocean. Following the closure of the early Paleozoic ocean basin, one part of the basic igneous rocks underwent HP/UHP metamorphism related to deep subduction, another part experienced only amphibolite-facies metamorphism. However, their igneous precursors are associated with continental rocks, supporting the model of the "in situ" relationship between eclogites, amphibolites and country rocks (gneisses).