A group of special sodium lamprophyre porphyry was found in the Mesozoic intracontinental extensional zone in northeastern Hunan, with significant differences between the major elements, trace elements and Sr, Nd isotopes and common potassium lamprophylas.
The rock is characterized by rich Na2O high TiO2 and Nb, Ta, Nd, LREE weak enrichment and no negative anomaly, trace elements and Sr. The Nd isotope composition has the properties of the mantle source area of ​​the oceanic basalt (OIB). The initial ratio of 87Sr/86Sr is 0.705332, the initial ratio of 143Nd/144Nd is 0.512650, and the ε Nd(t) is +3.5~+3.9.
The formation of a special source of sodium porphyry in the mantle source is mainly composed of fluids/melts from the asthenosphere containing volatiles and the original mantle at the bottom of the lithosphere. The isochron age of the Rb-Sr is 136.61 Ma, which represents the tectonic transition period from the extrusion to the extension of the Yanshan Mountains in the northeastern part of Hunan Province.
The sodium lamprophyre is formed in the mantle hotspot tectonic setting of the upwelling mantle in the continental aquifer. The upwelling of the asthenosphere is the main earth power that leads to the formation of sodium lamprophyre and restricts the late inland tension of the Yanshan Mountains in northeastern Hunan. Learning factors.
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