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Genesis And Relationship With The Iron Mine Of Ore-bearing Rock Mass In Laiwu Of Shandong Province

Posted on:2015-01-17Degree:MasterType:Thesis
Country:ChinaCandidate:L HanFull Text:PDF
GTID:2250330428969265Subject:Mineral prospecting and exploration
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The Zhang Jiawa Fe deposit in Laiwu of Shandong province is one typical skarndeposit with high-grade iron in the Eastern North China Craton.In this paper,based onthe collection and summary of the previous studies,we mainly studied the petrologicfeatures,major and trace elements characteristics,diagenetic age and ore-formingfluids of the host rocks,through the methods as downhole observation, electronmicroprobe analysis, major and trace elements and Sr-Nd-Pb-Hf isotopic analysis, etc.,furthermore, we also discussed the ore genesis and tectonic setting.The mainachievements that we obtained were as follows:(1)Downhole geological observation shows that the Ordovican limestone ofMajiagou Formation is the main ore-bearing layer.The distribution of ore bodies isspatially related to skarn,and there is a gradual transition between them.Main types ofthe ore are massive ores and disseminated ores,and the rock alteration developedcommonly.(2)The ore-forming rock mass of the deposit was related to the diorite of the lateyanshan epoch,and the lithologies are diorite and pyroxene diorite which are formedby the same host magma.The LA-ICP-MS zircon U-Pb dating results indicated thatthe Zhang Jiawa intrusive bodies were formed at (131±3)Ma,when is the strongestlithosphere thinning of the North China Craton.The dioritic intrusions are derivedfrom an amphibole-bearing spinel lherzolite source of lithosphere.The magma wascontaminated by crust when it is rising and emplacement.(3)The Zhang Jiawa diorites are characterized by SiO2content(53.15%~60.35%),Na2O+K2O content(5.10%~7.77%) and enrichment of magnesiumcontent(5.91%~10.98%).The chondrite-nomalised REE pattern shows LREEenrichment,and the high field strength elements such as Zr, Nb,Ta are significantlydepleted and lithophile elements such as Rb, Ba and Sr are enriched.(4)The isotopic characteristics indicated that the (87Sr/86Sr)i values range from0.70658to0.70833,which are close to the continental crust, and the εNd(t) valuesrange from-11.39to-15.20.This characteristics are similar to Adikite and indicatedthat there are some crust materials enter into the magma when it rising andemplacement.(5)The ore-forming fluids which played a significant role during the iron skarn mineralization was mainly derived from magma: the parental magma is enriched influids and volatile and further enriched by the fractional crystallization. The ironaccounted for the mineralization was leached from the intrusion and was mainlyderived from the magma.
Keywords/Search Tags:Skarn iron deposit, Diorite, Geochemical characteristics, Diagenetic age
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