The Lower Paleozoic carbonates of Tarim Basin were marbleized locally due to the thermal effects of magma intrusions. Marmorization is typical on the Tangwangcheng outcrop section in Bachu county at the northwestern margin of Tarim Basin and in cores from Well Zhong-16 in the Tazhong area. The characteristics of marmorization change regularly with the distance from carbonate rocks to intrusions. The degree of marmorization is high in the periphery of igneous intrusions with grains of marble being relatively coarse

but is progressively lowers and eventually disappears away from the intrusions. Grains of carbonate experienced marmorization show pseudo-hexagonal poikilitic structure with poorly developed secondary pores. Compared with the unaltered limestone

the marmorized carbonates have similar strontium isotope composition but slighter oxygen and carbon isotope compositions

indicating that the marmorization is a process dominated by thermal metamorphism. During this process

no extraneous fluids except for a small amount of formation water in the original carbonates are involved. The quality of marmorized reservoirs is basically similar with the unaltered limestone due to the absence of dissolution from extraneous fluids.