Characteristics and genesis significance of Titanium minerals of Baogutu porphyry copper deposit, Xinjiang
包古图斑岩铜矿床的钛矿物特征及其成因意义

On the basis of observing a large number of thin sections, assemblage characteristics and formation mechanism of titanium minerals in Baogutu porphyry deposit were studied. The main titanium minerals are sphene, ilmenite and rutile. Sphene formed during both rock-forming and ore-forming period, but mainly found in the potassium alteration stage of early ore-forming period and coexist with K-feldspar and biotite, while relative low content of sphene also formed in the propylitization and zeolitization stages. Ilmenites developed in every alteration stages of ore-forming period in which most common in the potassium alteration stage, while rare formed in rock-forming period. Rutile is only found in the ore-forming period, in which it coexists with K-feldspar, biotite, and quartz in the early potassium alteration stage and also wrapped in sphene as fine grains. Rutile formed in propylitization stage too and intergrowth with chlorite. These titanium minerals are mostly found within biotite grain or nearby, which may be one characteristics of porphyry deposit. SiO2 and CaO content of sphene is close to the theoretical value, while TiO2 content is lower. All the ilmenites contain Mn, with a MnO content of 1.97 to 4.49 percent and manganese ilmenite is appeared (MnO content 18.38 percent). Rutile contains a certain amount of SiO2 and FeO, with a small amount of Al2O3, MgO and P2O5 in some grains. Assemblage characteristics of titanium minerals shows that ore-bearing porphyry of Baogutu porphyry deposit belongs to I-type, forming at a high oxygen fugacity and not deep depth.