| The Sanjiazi scheelite deposit is located in the southern Daheishan-uplift of the Changbaishan uplift, which belongs to the eastern active margin of Eurasia plate. The southeast to studied area is Sino-Korea plate and northwest is Songliao rift. The major structures extend in NE-NNE direction. The Daheishan-uplift is bounded by two deep faults, Siping-Dehui and Yilan-Yitong.Palaeozoic rock series are metamorphism marine volcanic-sedimentary rock, locates in the uplift area. According to rock assembles and degree of metamorphism, the Palaeozoic strata can be classified as Cambrian Xiaodingshan formation, Ordovician Xibaoan and Shifeng formation, Devonian Xujiatun Carbonic Mopanshan and Permian Chengjiatun formations, Among them, Xujiatun group and Mopanshan formations maily composed of metamorphic volcanic rock and marble, have a close relationship with the scheelite mineralization.The studied area saw many magmatic activities from Caledonian orogeny to Yanshanian period. Intrusion with various size occur in the south of Daheishan-uplift with NE, taking up over 50% in whole area. The middle-late Jurassic intrusion rock is much more than others, present a simple ring in spatial. Many mineralization and mines are distributed around the contact belt between intrusions and . The studied area locates nearby this contact belt which is porphyritic-like monzonitic granite, fine-medium-grain monzonitic granite and the upper Devonian Xujiatun marble.The dominant structures of Sanjiazi scheelite deposit are contact belt structure and faults. The contact belt show itself between upper Devonian Xujiatun marble and middle-late Jurassic porphyritic-like monzonitic granite, fine-medium-grain monzonitic granite. The NE faults controlls not only intrusions, ore bodies as well as such dykes as granite aplite and diorite-porhyrite.Among 14 verified orebodies explored, they are laminated each other. The biggest orebody, in Sanjiazi mine, is long 500m, wide 160m and thick 4-29m, strike is NE(50°-70°),trending is SE and inclination is 10°-15°. There is often branch-complex in both profile and planum of orebody. The average grade of orebody is 0.276%. Metal minerals are composed of pyrite, scheelite, tungsten, bismuthinite, molybdenite, chalcopyrite, limonite and little pyrrhotite, automorphic-xenomorphic granular texture, metasomatic relict texture, remnant texture, skeletal texture, inclusion texture. Dissemination structure is main structure and rare stockwork. Scheelite and some tungsten make uo of the wolframium.Wall-rock alterations mainly include skarnization, feldsparation, hornatonation, silicification, chlorite, carbonation and some pyritization, galenation, blendenation, molybdenum and bismuth mineralization. The skarnization and silicification are contact with scheelite in temporal and spatial variation.Based on ore-forming geological factors, geological characters of deposit, trace element and REE, we can draw a conclusion that the major ore-forming materials come from middle-late Jurassic porphyritic-like monzonitic granite, fine-medium-grain monzonitic granite. Studies on geological and geochemical characters of the Sanjiazi scheelite deposit, together with the compareing of it with other main scheelite deposits, indicate that this deposit belongs to the skarn-type deposit.Studies of the geologic setting, geological characters and genesis of Sanjiazi scheelite deposit and geophysical and geochemical data in this area can give us such ore-finding clues as following.①geology information: the skarn belt is the main place of scheelite, middle-late Jurassic porphyritic-like monzonitic granite and fine-medium-grain monzonitic granite play the important intrusion conditions. NE and NW structure control the intrusion rock, and the primary tectonite of rock locating the scheelite orebody.②geochemical information: there are W and Mo anomaly area according to the soil surveying.③geophysical information: the induced polarization intermediate gradient surveying indicate that is the relative low-resistance and high-polarization anomaly area.According to studying on the ore-forming factors, geophysics, geochemistry and character of alteration, two potential metallogenetic areas are discussed. One is in the southwestern Sanjiazi mine, the other is locted in the Tiegongshan. These two areas have favourable ore-finding potentials and are worth further exploring.
|
PDF Full Text Request