Geological Characteristic and Protolith Nature of Yuqia Eclogite-type Rutile Deposit in Northern Qaidam UHP Metamorphic Belt

The Yuqia eclogite-type rutile deposit is the first large-super large rutile deposit discovered in Northern Qaidam ultra-high pressure metamorphic belt, which was related to the UHP eclogite.The flesh massive Ti-rich eclogite serves as the major ore-host rock for this rutile deposit, the rutile with four exiting state can be recognized in this deposit, representing for four different stages of formation and evolution, respectively.After the detailed field geological investigation and sampling, the eclogite-type rutile ore in the Yuqia deposit can be divided into high-grade ore (TiO₂>2%) and low-grade ore (TiO₂ < 1%~2%). The investigation results have shown that the high-grade ore are relatively depleted in SiO₂ while they are enriched in TFeO, MnO and P₂O₅, with lower Al₂O₃/TiO₂ ratios (<7) and higher content of total alkali (K₂O + Na₂O). Trace element characteristics indicate that the high-grade ore has the protolith characteristics of oceanic island basalt (OIB), but the protolith of low-grade ore was derived from the enriched type mid-ocean ridge basalts (E-MORB) in the intraplate environment.The different of protolith characteristics between Yuqia rutile ore with two types reflect the complexity of the tectonic evolution in Northern Qaidam ultrahigh pressure metamorphic belt.