| Langmugri research area is located in the eastern section of the famous East Kunlun metallogenic belt in Qinghai Province,and in Bokalik-Xiangride Indosinian gold,lead,zinc,copper and rare earth metallogenic belt.It is a very important mineral resources accumulation area in China.There are Asiha gold deposit,Nageng Kangqie silver deposit,Xiari Hamu Cu-Ni deposit and other typical deposits in East Kunlun,with a relatively high degree of mineral exploration and theoretical research;In recent years,the exploration and theoretical research of manganese deposits found in Hongshuihe,Santonggou north and other areas are relatively low.So this paper studies the genesis of the newly discovered Langmuri manganese deposit in order to provide a reference basis for the theoretical research and prospecting of manganese ore in Qinghai area.The tectonic location of Langmugri manganese ore area belongs to the north side of kunzhong fault zone at the eastern end of East Kunlun orogenic belt,and is located in the early Paleozoic oceanic-continental subduction zone.The strata exposed in the manganese ore area are Early Proterozoic Baishahe formation,Meso-Neoproterozoic Wanbaogou formation and quaternary system;F4,F18-21 and other fault structures are developed in the mining area,which are mainly distributed in Northwest and Northeast directions,and the secondary structures are relatively developed;The magmatic activity in the area is strong,which can be divided into Caledonian,Variscan,Indosinian and Yanshanian magmatic activities.Since the exploration of manganese ore in 2017,well exposed manganese ore deposits have been found in garnet quartzite strata of Wanbaogou Formation,and a total of three manganese ore bodies and twelve fracture alteration zones have been delineated,the manganese ore body are M1-1,M1-2 and M2-1 respectively,with a manganese ore grade of 22-32%;Through the observation of the geological characteristics and petrography of manganese ore,the mineral assemblage mainly includes pyrolusite,psilomelane,spessartine,rhodonite,etc.,which accords with the mineral assemblage characteristics of gondite series.The X-ray diffraction of manganese ore shows that manganese silicate minerals such as spessartine and rhodonite are present in the ore.In the mineral chemical characteristics of garnet and rhodonite,the garnet ring is not obvious,the main component is spessartine garnet,followed by almandite garnet,which is shown as ferritic spessartine garnet in the end-member mineral composition diagram.Rhodonite falls into the area of rhodonite in the composition diagram,and the Mn O content is37.87-49.51%,and manganese is relatively enriched.The main elements of garnet quartzite in host rock are rich in manganese(11.27-15.70%),poor in sodium(0.02-0.03%),poor in potassium(0.04-0.05%),low in Mg(0.27-0.49%)and low in Ti(0.35-0.53%).The rare earth elements are relatively depleted in LREE and enriched in HREE,and the fractionation degree of REE is obvious.The trace elements are relatively enriched in Th,U,Ta,La,Ce and other elements,and depleted in Rb,Ba,Nb,P,Sr and other elements;The main elements of plagioclase-hornblende rock in the underlying stratum are generally rich in aluminum(14.13-15.43%),poor in sodium(3.07-3.73%),poor in potassium(0.88-1.16%)and low in Ti(1.10-1.12%).The rare earth elements are relatively enriched in light rare earth elements HREE is relatively depleted,with europium weak positive anomaly and less obvious cerium anomaly.Trace elements are relatively enriched in Ba,K,P and depleted in High field strength elements such as Nb and Ta.Fluid inclusions in quartz and rhodonite from manganese ore area are CO2-Na Cl-H2O,medium and high salinity,medium and high density,medium and low temperature fluid system.The middle-high salinity and middle-high density indicate that the manganese ore was formed in Marine sedimentary environment,while the middle-low temperature indicates that the manganese ore experienced magmatic hydrothermal fluid activity in the later stage of sedimentation and mineralization;The salinity of the fluid is 9.8-21.9 wt.%Na Cl eqv.,the homogenization temperature is158.9-294.3?,the fluid density is 0.55-1.06 g/cm3.U-Pb chronology analysis of garnet quartzite and plagioclase-hornblende rock shows that garnet quartzite were deposited at 1419-1584 Ma,which belongs to the middle proterozoic period and represents the age of manganese deposit and mineralization,and combined with the analysis of metamorphic peak ages of garnet quartzite and plagioclase-hornblende rock,the manganese ore area experienced two periods of intense metamorphic transformation between 569-713 Ma and 435-489 Ma;According to the proto-rock restoration and tectonic environment analysis,the proto-rock of garnet quartzite is volcanic-sedimentary series,and the Mn O/Ti O2 value is29.5-32.7,indicating that it was formed in seawater sedimentary environment;The plagioclase-hornblende rock protolith is a basic volcanic rock derived from mantle and accompanied by crust-mantle mixing.Based on the comprehensive study of ore deposit geological characteristics,rock ore petrography,rock geochemistry,mineral chemistry,metallogenic fluid characteristics and metallogenic chronology in the manganese ore area,it is considered that langmuri manganese deposit in garnet quartzite has mainly underwent sedimentary mineralization,metamorphic remolding,and its genetic type belongs to typical sedimentation-metamorphic manganese ore. |
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