Volcano-Magma-mineralization Processing And Metallogenic Prediction Of Dazhongtiao Area

Dazhongtiao area is an important non-ferrous metal base in China. Over the years, manyexperts and scholars carried out a lot of researches systematically in this area, especially in thenortheast section. A number of important research results have been obtained in ore deposit,geochemistry, ore genesis, metallogenic setting and ore prospecting. But the research level tothe southwest section is still very low, and the achievements are rather few. After fullcollecting and systematic analyzing on researches by the predecessors and being guided bythe theory of metallogenic series, the author, focusing on the new progress of ore prospectingin the southwest section of Zhongtiao Mountains in recent years, carries out the followingresearch works: studying the typical ore deposits, analyzing the diagenetic mineralizationconditions and ages, determining the metallogenic series of Dazhongtiao area andsummarizing the metallogenic regularities. On the basis of the above works, this PhDdissertation also carries out metallogenic prediction and favorable metallogenic target areadelineation to provide the basis for further mineral exploration. And the followingachievements and conclusions have been obtained:1.The regional deep tectonic characteristics have been studied by analyzing the regional1:200000aeromagnetic and gravity data. It is put forward that the deep structure of ZhongtiaoMountains is characterized by the steep contact zone between the thickening block oflithosphere and the upwelling of asthenosphere. And the sloping direction of the soft-hardcontact is corresponding to the gravity gradient belts, which is perfectly consistent with thepiedmont fault in the northwest edge of Zhongtiao Mountains. Bounded to this fault, the deepstructure of Zhongtiao Mountains can be divided into two units. The northwest unit Yunchengbasin belongs to lithospheric thickening area. The southeast unit is Zhongtiao Mountains withlithospheric thinning. Along the soft-hard contact zone and its both sides, there developed latearchean-paleoproterozoic-middle late proterozoic ultrabasic rocks, basic complex rocks, acidmagmatic rocks, and Yanshan period acidic-alkaline magmatic rocks in multiple stages. Thefault zone is deeply controlled by magmatic deposit mineralization in Zhongtiao Mountainsarea. In combination with the regional tectonic background of Dazhongtiao Mountains, thefracture structure division in Dazhongtiao area is made in this dissertation.2. Focusing on the new progress of ore prospecting in the southwest section ofZhongTiao Mountains in recent years, we adopt many research means such as petrology,mineralogy, lithology, ore deposit geochemistry, and isotope geochemistry to study the typicalore deposits in this area. The dissertation puts forward that Taohuadong copper is a basic magma segregation-eruption-sedimentary deposit. The ore genesis ofgold-silver-copper-polymetallic deposit in the type of Donggou-calcite vein is significantlydifferent from that of Hujiayu and Bizigou copper deposits, which has the possibility ofmantle-derived magmatic fluid mineralization directly. So there still are good prospects forfurther exploration in the deeper part. At the same time, scheelite has been found inDonggou-calcite vein. And the mineralogical characteristics of the scheelite are also studied inthe dissertation. The research achievements of newly discovered deposits enrich the study toore deposits in Zhongtiao Mountains and expand the prospecting idea, which has an importantguiding significance in looking for similar ore deposits in Dazhongtiao area.3. Isotope chronology methods have been used to discuss the diagenetic mineralizationage in Dazhongtiao area. With LA-ICP-MS analysis technology, the magma crystallizationages for zircons in grey gneisses, amphibolites and monzogranites of Zaizi-Xiyao in Sushuicomplex in Taohuadong copper mining area are obtained respectively to be2625±15Ma,2592±16Ma and2548±15Ma. The ages of ancient-inherited zircons in rocks are respectively2790±15Ma,2773±24Ma and2782±34Ma. The zircons of which ages are older than2700Ma can be checked in all the three types of rocks with different formation sequences. Andtheir ages are very close with each other. The results above prove that the initial diagenesisage of Sushui complex is archaeozoic era. The ages of magnetite ore body, mineralizationgranodiorites, and monzonitic granites in Yitang iron nickel deposits are also obtainedrespectively to be2317±33Ma,2151±20Ma and1930±83Ma. It proves that the genesis of orebasic igneous rock and magnetite belongs to magmatic liquation and crystal gravitydifferentiation. With Re-Os isotope chronology research methods, the age of molybdenite inSanchagou Au-Mo ore district is obtained to be1823±23Ma. The determination results ofore-forming age show that the metallogenic phases of Zhongtiao Mountains area havemulti-episodic characteristics.4. The deposit types and mineral distribution in Dazhongtiao area are summarized in thisPhD dissertation. By using the theory of metallogenic series, and taking the tectonic cycle ofproterozoic as the main line, the author has established the archean-proterozoic depositmetallogenic series. The Precambrian ore deposit metallogenic series in Dazhongtiao area aredivided into two metallogenic series combination, five metallogenic series types, sixmetallogenic series, and seventeen metallogenic sub-series. Fourteen prospecting target areasare delineated in Zhongtiao Mountains area. And three of them are verified to have goodprospecting effect. This research provides abundant data for the determination of the nextprospecting direction.