| Jiaodong is one of the most important gold mining areas in China, with provengold reserves of about1/4of the whole national gold production. In addition, there aremany other nonferrous metals such as copper, molybdenum, lead, zinc, silver, etc.deposits in the region. However, little work has been done about these deposits, andthe relationship between the gold deposits and the nonferrous metal deposits remainsunclear so far.The nonferrous metal deposits including molybdenum, copper, lead, zinc andsilver distribute in the middle and eastern Jiaodong region, and are associated closelywith Weideshan granite. The mineralogenetic epoch is Mesozoic Cretaceous period,thus they should belong to a mineralogenetic series with consanguineous relation ofepoch, space, and genesis. On the background of the lithosphere thinning in theeastern China during Mesozoic, large-scale magmatic activities occurred in Jiaodongarea, among which the Weideshan granite formed in early Cretaceous as the largestintrusive body. It produces much heat resulting in strong liquid activity, ore-formingmaterials activation, transfer, and enrichment. At last different elements deposited toform different styles of deposits.This paper analyzing ore formation rules and ore-controlling factors ofnonferrous metal deposits in Jiaodong area, and then selects two typical depositswhich were explored in recent years—Shangjiazhuang molybdenum deposit, andDadengge complex deposit to do some researches at depth. The main target is to findthe origin of the ore materials, physicochemical condition, mineralization age, and themineralizing mechanism. Based on the analysis above, we conclude that themolybdenum, copper, lead and zinc complex deposit is a metallogenic series which isassociated strongly to the Weideshan granite We find the mineralization age of gold deposits in Jiaodong region is consistentwith the diagenesis epoch of Weideshan granite. Some researchers pointed out that thegranite body has consanguineous relationship with the gold deposits formation.Therefore, we select a typical deposits, which was explored in recent years—Jiaojiagold deposit, to do some researches at depth. We analyzed the geochemicalcomposition of bulk rock, REE and trace elements, stable isotopes, fluid inclusions ofore rocks, and then pointed out the gold metallization is related to the Weideshangranite. However, Weideshan is a very complicated granite body, it is difficult to findout which phase of magmatic activity bring gold.The main conclusions are as following:(1) The REE Chondrite-normalized patterns and the trace elements clusteranalysis of quartzes of ores in Shangjiazhuang molybdenum deposit and Dadenggecomplex deposit show that: the ore-forming materials of Shangjiazhuangmolybdenum deposit root directly in Weideshan granite, the ore-forming materials ofDadengge complex deposit have two origins: the lead and zinc deposits root insupracrust, and the gold, copper, molybdenum, and silver deposits derive fromWeideshan granite.(2) δ34SCDT=4.5‰in Shangjiazhuang molybdenum deposit, and δ34SCDT=7.0～7.1‰in Dadengge complex deposit, the average value is7.05‰, we suggested thatboth of the sulfur isotopes came from mixed origin. The sulphur isotopes ofShangjiazhuang molybdenum deposit is lower, which means it may originate fromdeeper magma chamber and didn’t be contaminated by sequent geological events.(3) The lead isotopes of Shangjiazhuang molybdenum deposit and Dadenggecomplex deposit are all near the earth mantle’s value, some near crust evolvement line,and some near fold belt evolvement line. We suggested the lead is from mixed origin.They are all old abnormal lead. The lead of Shangjiazhuang molybdenum deposit rootin Weideshan granite and the lead of Dadengge complex deposit root in supracrust.(4) The Re-Os isotopic dating of3molybdenite samples from Shangjiazhuangmolybdenum deposit has yielded a precise age of115.5±1.6～117.6±1.6Ma, andalmost at the same time of the formation of the Weideshan granite. The Re isotopecomposition shows the ore-forming materials originate from Weideshan granite. Thusthe molybdenum deposit is associated closely with the Weideshan granite.(5) Whereas the copper deposits, lead and zinc deposits, molybdenum depositsdistributearound the Weideshan granite, the mineralization age is consistent withdiagenesis, the ore-forming materials is directly or indirectly originated from this granite. Therefore, we suggested that the molybdenum, copper, lead and zinc complexmetal deposits in Jiaodong area are a metallogenic series, which is related to theWeideshan granite, and have the feature of porphyritic deposits.(6) We do some researches on the distribution model of the copper deposits,lead and zinc deposits, molybdenum deposits in Jiaodong area. The copper depositsare mainly located in the interlayered structures of Jingshan Group around theWeideshan granite; the lead and zinc deposits are mainly in the outside contact zoneof the Weideshan granite; the molybdenum deposits are within the Weideshan granite,and they were controlled by various structures.(7) We build the metallogenic model of the molybdenum, copper, lead and zinccomplex metal deposits. The hydrothermal fluids from the Earth mantle exchangedand extracted the metallic materials from the country rocks to be ore-forming fluids.As the fluids ascending, the temperature and pressure drop down. When the fluidarrives near the earth surface, the system becomes open. With the involvement ofatmospheric water the ore-forming fluid decomposes and forms various styles ofmetallic deposits. The locations of different deposits are strictly restricted by thedistance from the Weideshan granite. Within the granite, the temperature is higher andis suitable for Mo deposition, and the temperature near the granite is moderate,suitable for copper, lead, and zinc deposits formation.(8) Research on gold metallization of Jiaojia gold deposit shows that: the REEChondrite-normalized patterns of pyrites and quartzes of ores in Jiaojia gold deposit atdepth are similar to the REE patterns of Weideshan granite. This indicates thatWeideshan granite provide certain ore-forming materials for mineralization. δ34SCDT=7.5～9.8‰, the mean value is8.6‰in deep portion of the Jiaojia deposit, lowerthan the shallow parts of the deposit (the average value of10.06‰). This indicatesthat the δ34S is descending from shallow to deep, implying the material from Earthmantle. The lead isotopes of Jiaojia gold deposit at depth are between the Earthmantle evolvement line and fold belt evolvement line, thus we think the lead is frommixed origin. They are all old abnormal lead. The lead of Jiaojia gold deposit at depthroot in Linglong granite, and the Precambrian metamorphic rocks also provide somematerials.(9) Our results showed that the mineralogenetic epoch of gold deposit andmolybdenum, copper, lead and zinc complex metal deposits are consistent, alsoaccord to the diagenesis epoch of Weideshan granite. They are all associated stronglyto the lithosphere thinnng and large-scale magmata intrusions in the Cretaceous period. The Weideshan granite didn’t only offer materials for molybdenum, copper, lead andzinc complex metal deposits, but also offer energy and certain material for golddeposits. But we are not sure which evolvement phase of Weideshan granite bringsgold metallization based on the existing research. |
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