Y.M. Zhao’s research while affiliated with Chinese Academy of Geological Sciences and other places

The Galinge skarn iron deposit is located at the junction between the Qimantag metallogenic belt in the East Kunlun Mountains and the Qaidam Basin. There are two types of Fe-Ti oxides coexisting assemblages in the Galinge skarn deposit: one is the hydrothermal magnetite-ilmenite coexisting assemblage (HYM) which was discovered in No. 2 II ore group, whereas the other one is the igneous magnetite-ilmenite coexisting assemblage (IGM) which is developed in the fresh mafic basaltic andesite. This research aimed to analyze the distinctive composition and significant thermodynamic features of the HYM and IGM. The HYM shows an intergrowth with ferromagnesium spinel, and the crystallographic orientation of growing ilmenite lamellae are parallel to the (111) planes of the magnetite octahedron. Based on the equilibrium of oxidation, the equilibrated temperatures range between 581.8C and 688.9℃, and the oxygen fugacities vary between 10-14.74 and 10-17.94. The IGM is mainly in equilibrium with silicate minerals in the mafic magma. The equilibrated temperatures of the IGM range between 690.73℃ and 740.26℃, and the range of oxygen fugacities is 10-15.44-10-17.30. It is reasonably inferred that the primary metallogenic temperature might have reached 700℃, approaching the crystallographic temperature of water saturated magma. Therefore, the HYM was formed after the primary cooling procedure of the early high-temperature and high-salinity hydrothermal fluid which evolved from the magma. Because of the infiltration metasomatism between the hydrothermal fluid and the mafic igneous rocks, large amounts of metal elements such as Fe, Ti, Al, Mg and Cu were leached out. In the early high temperature setting, Ti and Al were incorporated into the magnetite, and consequently the oxyexsolution of titaniferous magnetite resulted in the intergrowth of magnetite and ilmenite. As the oxyexsolution did not rapidly re-equilibrate under new conditions, the iron-titanium oxide relationship could be preserved and hence could indicate the equilibrium temperature and the oxygen fugacity of the oxidation.

Located in Qimantage area of southwest Qaidam basin, Kaerqueka copper polymetallic deposit is a characteristic hydrothermal vein-skarn ore deposit controlled by the fractured and altered zone. Two kinds of wall-rock alterations can be recognized in the ore deposit, i. e., skarn and phyllic alteration. The former was formed by intrusion of Indosinian porphyaceous biotite adamellite. Copper polymetallic skarn lenticular bodies are commonly seen in the contact zone of the intrusion, different lithologic interfaces and faulted structural zones of the surrounding rocks. There are some typical calcium skarn minerals, such as diopside, hedenbergite, andradite, hessonite, idocrase, wollastonite, epidote, scapolite and actinolite. The latter forms many parallel NWW-striking chacopyritized hydrothermal alteration zones in porphyaceous biotite adamellite in the northwest part of the ore district, belonging to hydrothermal vein type mineralization controlled by faulted fractured zones. It is concluded that Kaerqueka copper polymetallic deposit is related to Indosinian hypabyssal and high emplacement porphyaceous biotite adamellite. The ages of rocks and ores in the copper polymetallic skarn deposit and the veinlet-disseminated hydrothermal veinlike copper deposit are the same, and the backgrounds of tectono-magmatic activities are identical; nevertheless, they are products of different ore-forming processes that occurred at different stages, different depths and different parts. This ore deposit is a compound one, with the skarn copper polymetallic mineralization as the main body, accompanied by the hydrothermal vein type copper mineralization in well-developed faults of the parent rock.