矿床地球化学国家重点实验室知识库

The development of Early Cretaceous mafic dikes in northern and southern Jiangxi allows an understanding
of the geodynamic setting and characteristics of the mantle in southeast China in the Cretaceous. Geological and
geochemical characteristics for the mafic dikes from the Wushan copper deposit and No. 640 uranium deposit are given in
order to constrain the nature of source mantle, genesis and tectonic implications. According to the mineral composition,
the mafic dikes in northern Jiangxi can be divided into spessartite and olive odinite types, which belong to slightly
potassium-rich calc-alkaline lamprophyre characterized by enrichment in large ion lithophile elements (LILE) and light
rare earth elements (LREE), large depletion in high strength field elements (HSFE) and with negative Nb, Ta and Ti
anomalies, as well as 87Sr/86Sr ratios varying from 0.7055 to 0.7095 and 143Nd/144Nd ratios varying from 0.5119 to 0.5122.
All features indicate that the magma responsible for the mafic dikes was derived mainly from metasomatic lithosphere
mantle related to dehydration and/or upper crust melting during subduction. Differences in geochemical characteristics
between the mafic dikes in northern Jiangxi and the Dajishan area, southern Jiangxi were also studied and they are
attributed to differences in regional lithospheric mantle components and/or magma emplacement depth. Combining
geological and geochemical characteristics with regional geological history, we argue that southeast China was dominated
by an extensional tectonic setting in the Early Cretaceous, and the nature of the mantle source area was related to
enrichment induced by asthenosphere upwelling and infiltration of upper crust-derived fluids responding to Pacific Plate
subduction.