摘要
This paper reports the systematic studies of geochemistry on the meta sedimentary rocks, felsic gneisses and amphibolites of the Kongling complex from the Archean high grade terrain of the Yangtze craton. It shows that the amphibolites originated from a weakly depleted mantle resource. Nb negative anomaly, negative ε (Nd, t ) and the t DM ages which older than their isochron ages of the TTG gneisses imply the possible existence of the crust older than round about 2.7 Ga in the region. Three types of meta sedimentary rocks are identified from the Kongling complex. The first type originated from the juvenile crust with the features of the first cycle sedimentary rocks. Cratonic sedimentary rocks characterize the second type. Mobilization of REE and other elements resulted from partial melting during the migmatization is found in the third type of meta sedimentary rocks. Apart from the early TTG gneisses, some of the mafic rocks are also expected to be the source rocks of the first type of para rocks. The deposition times of the first and second type paragneisses are closed in the Neoarchean of about 2.7 Ga and the early period of Proterozoic respectively, and the period when cratonization of the Yangtze continental block completed is referred to be earlier than the Mesoproterozoic. Nd isotopic tracing on the magma sources of the Jinning granitic rocks in the region reveals that the major part of the Kongling basement is Neoarchean.
This paper reports the systematic studies of geochemistry on the meta sedimentary rocks, felsic gneisses and amphibolites of the Kongling complex from the Archean high grade terrain of the Yangtze craton. It shows that the amphibolites originated from a weakly depleted mantle resource. Nb negative anomaly, negative ε (Nd, t ) and the t DM ages which older than their isochron ages of the TTG gneisses imply the possible existence of the crust older than round about 2.7 Ga in the region. Three types of meta sedimentary rocks are identified from the Kongling complex. The first type originated from the juvenile crust with the features of the first cycle sedimentary rocks. Cratonic sedimentary rocks characterize the second type. Mobilization of REE and other elements resulted from partial melting during the migmatization is found in the third type of meta sedimentary rocks. Apart from the early TTG gneisses, some of the mafic rocks are also expected to be the source rocks of the first type of para rocks. The deposition times of the first and second type paragneisses are closed in the Neoarchean of about 2.7 Ga and the early period of Proterozoic respectively, and the period when cratonization of the Yangtze continental block completed is referred to be earlier than the Mesoproterozoic. Nd isotopic tracing on the magma sources of the Jinning granitic rocks in the region reveals that the major part of the Kongling basement is Neoarchean.
