Early Cambrian and Mid--Late Neoproterozoic volcanic rocks in China are widespread on several Precambrian continental blocks, which had aggregated to form part of the Rodinia supercon- tinent by ca. 900 Ma. On the bas...Early Cambrian and Mid--Late Neoproterozoic volcanic rocks in China are widespread on several Precambrian continental blocks, which had aggregated to form part of the Rodinia supercon- tinent by ca. 900 Ma. On the basis of petrogeochemical data, the basic lavas can be classified into two major magma types: HT (Ti/Y 〉 500) and LT (Ti/Y 〈 500) that can be further divided into HT1 (Nb/La 〉 0.85) and HT2 (Nb/La ≤ 0.85), and LT1 (Nb/La 〉 0.85) and LT2 (Nb/La ≤ 0.85) subtypes, respectively. The geochemical variation of the HT2 and LT2 lavas can be accounted for by lithospheric contamination of asthenosphere- (or plume-) derived magmas, whereas the parental magmas of the HT1 and LT1 lavas did not undergo, during their ascent, pronounced lithospheric contamination. These volcanics exhibit at least three characteristics: (1) most have a compositional bimodality; (2) they were formed in an intracontinental rift setting; and (3) they are genetically linked with mantle plumes or a mantle surperplume. This rift-related volcanism at end of the Mid-- Neoproterozoic and Early Cambrian coincided temporally with the separation between Australia-- East Antarctica, South China and Laurentia and between Australia and Tarim, respectively.展开更多
基金financial support from the Land and Resources Survey Project of China(Grants # 1212010611804, 121201120133)the National Natural Science Foundation of China(Grant # 40472044)
文摘Early Cambrian and Mid--Late Neoproterozoic volcanic rocks in China are widespread on several Precambrian continental blocks, which had aggregated to form part of the Rodinia supercon- tinent by ca. 900 Ma. On the basis of petrogeochemical data, the basic lavas can be classified into two major magma types: HT (Ti/Y 〉 500) and LT (Ti/Y 〈 500) that can be further divided into HT1 (Nb/La 〉 0.85) and HT2 (Nb/La ≤ 0.85), and LT1 (Nb/La 〉 0.85) and LT2 (Nb/La ≤ 0.85) subtypes, respectively. The geochemical variation of the HT2 and LT2 lavas can be accounted for by lithospheric contamination of asthenosphere- (or plume-) derived magmas, whereas the parental magmas of the HT1 and LT1 lavas did not undergo, during their ascent, pronounced lithospheric contamination. These volcanics exhibit at least three characteristics: (1) most have a compositional bimodality; (2) they were formed in an intracontinental rift setting; and (3) they are genetically linked with mantle plumes or a mantle surperplume. This rift-related volcanism at end of the Mid-- Neoproterozoic and Early Cambrian coincided temporally with the separation between Australia-- East Antarctica, South China and Laurentia and between Australia and Tarim, respectively.