Abstract:

Mg-rich marble is the mainly host rock of borate deposit in Zhuanmiao borate ore district in Eastern Liaoning. The petrologic features,chemistry of the whole rock,REE and trace elements, and C,O isotope geochemistries of Mgrich marble are studied in this paper. The results show that Mg-rich marble has the characteristics of magmatic carbonatite: the major elements indicate that the rock is rich in Mg and Si. With relatively high trace elements contents of B，F，Rb，Cs，Th，U and comparatively low contents of V，Cr，Co，Ni,HFSE, the related ratios are similar to those of magmatic carbonatite. The  contents of REE are relatively low，showing a LREE-rich pattern in the figure of chondrite-normalized REEpattern，and in concordance with ultramafic peridotite in Houxianyu. Carbon and oxygen isotopic compositions of whole-rock samples lie within ranges of -2.6‰ to +5.59‰ for δ13C and 12.91‰ to 20.95‰ for δ¹⁸OThe δ¹³C and δ¹⁸O values of Mg-rich marble fall on the zone of primary and marine carbonatite in the diagram of δ¹⁸O-δ¹³C.The contents of carbon and oxygen isotope are higher than those of magmatic carbonatite all over the world，which may be concerned with the contamination of crustal materials.

Key words: Mg-rich marble;B-bearing rock;magmatic carbonatite, Zhuanmiao borate ore district in Eastern Liaoning