| Lietinggang iron-copper poly-metallic deposit is governed by Mendui ruralvillage of Duilongdeqing county.The tectonic position is Ladakh-Gangdese-Xiachayumagma arc belt of Gangdese-Himalayan orogenic system. This island arc belt mainlyexperienced three strong tectono-magmatic evolution stages, include subduction typevolcanic-magmatic arc in Jurassic-cretaceous, collision type volcanic-magma arc inPaleogene, magma events after collision in Neogene. At the same time it developed alot of plutonic intrusive rock and volcanic rock. It provides for the formation of aseries of porphyry copper-molybdenum deposit and the skarn type iron-copperpoly-metallic deposit which associated with Gangdese orogenic belt formed acidicrock mass in a very favorable geological and tectonic conditions.Lietinggang iron-copper poly-metallic mining area have a large number ofYanshanian granodiorite. They distributed a large area in the southeast, southwest,central and north mining area, with a batholith or rock strain state output. Rock ismainly gray with porphyric texture and graphic texture and blocky structure. Orebodies is obviously controlled by Sangqiu-Zhikong fault zone. The fault zone islocated in the southern of Nyainqentanglha Range. The ore mainly presents in skarnzone, which is occured in the contact area between the marble and limestone ofMailonggang group (T3m) in upper Triassic system and granodiorite in lateYanshanian. Ore bodies and wall rock boundary is the gradient relationship. On themacro, the ore’s output state is stratiform or bedded along the skarn, but part is cysticand lenticular.The skarn of Lietinggang mine area is mainly gray or dark green diopside skarnand garnet skarn. It has the following several kinds of structure, such as fine-grain ofblastic texture, replacement texture, metasomatic residual texture, fiber-like crystaltexture, generally has the massive structure. Skarn minerals are mainly composed ofgarnet, diopside, tremolite and actinolite, rocks, augite, and quartz, calcite, etc., andthere are a small amount of epidote, chlorite, tourmaline, wollastonite and fluorite, etc.At home and abroad, the research about the formation of skarn deposits has beenvery mature. At present a lot of research results have been obtained about theformation of geological and structural condition, rock geochemical characteristics, oredeposit geochemical characteristics, ore control factors and genetic model. Due to theLietinggang iron-copper poly-metallic deposit is a newly discovered poly-metallicdeposits in the Gangdese tectonic belt of Qinghai-Tibet Plateau. It basically has notbeen carried out research work systematically about deposit geology, geochemistry,fluid inclusion, mineragraphy and genesis of mineral deposit. Therefore, this thesiswill study the characteristics of metallic ore microscopy as the breakthrough point. Iam trying to establish the metallic minerals time pedigree of this iron-copperpoly-metallic deposit, further to divide the formation sequence of ore mineral,metallogenic stages and mineralization period. All of this to provide basicmineragraphy data to establish genetic model of deposit.Through the field geological investigation of Lietinggang iron-copperpoly-metallic deposit, I generally mastered the regional metallogenic geologicalbackground of deposit formation. By participating in the census geological work ofthe ore deposit, I fully understand the quantity, scale and occurrence of ore bodies,mastered the output layers, wall rock alteration and the main control factors of orebodies. On the basis of systematically rock collection, observation and research in theore samples, as well as its macroscopic characteristics, especially carry out a deepinvestigation for the veins in the field, we could understand the interpenetratingrelationship of the minerals and their symbiotic relationship.The major metallic minerals of Lietinggang iron-copper poly-metallic deposit aremagnetite, pyrrhotite, chalcopyrite, pyrite, molybdenite, tetrahedrite, chalcocite,azurite, bornite, covellite, galena, sphalerite, bismuth ore, malachite, hematite,limonite, et al.By grinding lots of polished section, we then carried out a systematicallyidentification and study for them. As a result, we basically understood their metallicminerals category, mineral relationships in the macro and micro (ore structure) aspectsalong with the ore structure. On the basis of all the above, we could then sort out theformed sequence of the metallic minerals, which offered solid and reliableinformation for the division of the ore-forming stage and mineralization periods.In this thesis, the generate sequence of ore minerals is listed as: magnetiteâ†'hematite+magnetite+pyrrhotite (small)â†'pyrrhotite+molybdeniteâ†' chalcopyrite+molybdenite+bismuthinite+bornite+pyriteâ†'chalcopyrite+pyrite+chalcocite+galena+sphaleriteâ†'limonite+copper blue+malachite. Thewhole ore-deposit was formed through the skarns stage, quartz-sulphide period andthe supergene period. In the meantime, the skarns stage was further divided as earlyskarns stage, late skarns stage and oxide stage. The quartz-sulphide period was furtherdivided as early sulfide stage and late sulfide stage.By summing up all those structure, construction, ore minerals and ganguemineral assemblage characteristic of the ores, we could draw a conclusion that theLietinggang iron-copper poly-metallic deposit belongs to the typical skarn depositscategory. |
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