Formation age of ore-bearing strata of the Zankan iron deposit in Taxkorgan landmass of Western Kunlun Mountains and its geological significance

Abstract: The Bulunkuole Group is one of the main components of Taxkorgan landmass in the Western Kunlun area, and is also important ore-bearing strata of the regional iron deposits. Recently, many large-sized iron deposits were found within the Bulunkuole Group, such as Zankan, Laobing, Mokaer and Yelike iron deposits. On the basis of detailed?petrography?features and SHRIMP U-Pb zircon dating of metamorphic rock and magmatic rock in the intrusion strata of the Bulunkuole Group from the Zankan iron deposit, the authors discussed the formation age of ore-bearing strata, and investigated the ore-forming age. The results show that the formation age of the representative magmatic zircon from plagioclase-hornblende schist in Bulunkuole Group is (1845.0±11.0) Ma, suggesting that ore-bearing strata are younger than (1845.0±11.0) Ma. Zircon SHRIMP dating of plagiogranite porphyry that intruded into the strata yielded a U-Pb age of (544.5±4.7) Ma, suggesting that the ore-bearing strata are older than (544.5±4.7) Ma. Thus the ore-bearing strata were formed during 1845.0?544.5 Ma. Moreover, SHRIMP dating of the zircon core from dacite yielded U-Pb ages of 3048.0?3054.0 Ma and 2032.0 Ma, indicating that there possibly exists an early Proterozoic or Archean basement in the surveyed area and adjacent areas, which is of important significance for recognizing Bulunkuole Group and the basement of Taxkorgan landmass. Bulunkuole Group outcropped in Taxian-Waqia uplift zone is one of the earliest strata in Western Kunlun Mountains, and this provides a basis for the existence of Taxkorgan paleo-landmass. Comparative researches on different types of deposits indicate that the Zankan iron deposit was mainly produced by the sedimentary mineralization process, and iron bodies with iron-bearing rocks of Bulunkuole Group were syngenetic, and hence the mineralization age of the Zankan iron deposit is Proterozoic, which is in accordance with the formation age of Bulunkuole Group and is also a very important period for the generation of global iron deposits.