Petrologic And Mineralogical Metamorphic Evolution And Metallogenic Significance Of Dingchachashan Titanium Deposit In North Qaidam

As one of the important strategic minerals,titanium supports the development of many strategic industries and is of great significance to the security of mineral resources in China.Located in the Ultra-high pressure metamorphic belt in the northern margin of Qaidam in the eastern margin of Qinghai-tibet plateau,the Dingchachashan titanium deposit is the first superlarge metamorphic eclogite type titanium deposit in the region.The eclogites in the study area are mostly in the form of nervation,lentoid or stratiform-like in the Jinshuikou group and ultramafic rocks.The length of the eclogites is >700 m.According to the analysis of the geochemical characteristics of the whole rock,the original rocks of eclogite have the characteristics of normal mid-ocean ridge basalt,transitional type and enriched in-plate basalt.To explore the cause of Dingchachashan titanium mineralization mechanism,this research subject on the basis of the studies of the ore deposit geology,divided the metallogenic stage,set the metallogenic stages mineral combination,and use the scanning electron microscope(SEM),electron microprobe(EPMA),typical minerals in situ LA-ICP-MS trace elements and the whole rock geochemical test and the mineralography and mineral geochemistry,rock mass to study the genesis and metallogenic tectonic background.Field investigation and mineral chemical test(SEM and EPMA)results show that:(1)Titanium-bearing minerals mainly include rutile,ilmenite and sphene,while the symphytes are mainly garnet and pyroxene,and a small amount of silica-rich phengite,apatite,plagioclase,zircon and other minerals are also visible.(2)The garnet composition zonation has stage IV growth,inclusions in garnet in particle size or how many,?: A round oval containing small particles of quartz,mica and titanium iron ore;?: Contain more inclusions,a sifter-like structure of metamorphosis,inclusions are mainly composed of ilmenite,quartz,a small amount of mica and apatite;?: Almost no inclusion;?: Containing several groups of oriented array of ilmenite and rutile,as well as biotite,white mica,quartz,zircon and apatite;The composition profile shows symmetrical change rule.(3)Rutile has obvious ? Ce(0.08 ? 2.69)and ? Eu(0.48 ? 8.83)abnormal fractionation.Whole rock geochemistry indicates that the tectonic environment formed by the original eclogite of Dingchachashan is characterized from normal mid-oceanic ridge basalt(N-MORB)to transitional or intraplate enriched mid-oceanic ridge basalt(E-MORB).According to previous studies and this study,the ore-forming period of eclogite in the Dingchachashan deposit is late Silurian epoch(429.4 ± 4.4 Ma),the diagenetic temperature is 618 ? 887 ?,and the diagenetic pressure is 2.5 GPa.Combined with previous data,geochemical and age of ultrahigh pressure eclogite primary and rutile mineral garnet comprehensive research,summarizes the eclogite type titanium deposit metallogenic restriction conditions,traces the tectonic environment of eclogite,orogenic evolution,reveal the metamorphism and metallogenic conditions,the ultra high pressure metamorphic eclogite in the studied area of petrology,mineralogy,isotope chronology research plays a vital role,thus summing up the original rocks of eclogite type,tectonic environment and titanium deposit metallogenic instruction significance.