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1、f第43卷第4期Vo1.43,No.4,386—3982014年7月GEoCHIMICAJuly,2014貴州天柱早寒武世黑色巖系重晶石礦床有機(jī)地球化學(xué)研究韓善楚2,胡凱,曹劍(1.南京大學(xué)地球科學(xué)與工程學(xué)院內(nèi)生金屬礦床成礦機(jī)制研究國家重點實驗室,江蘇南京210023;2.東華理工大學(xué)核資源與環(huán)境教育部重點實驗室,江西南昌330013)摘要:貴州天柱大河邊早寒武世黑色巖系重晶石礦床在全球同類礦床中儲量最大,是研究的熱點,含礦巖系富有機(jī)質(zhì),但對其研究薄弱。本文對這些有機(jī)質(zhì)新進(jìn)行了系統(tǒng)的有機(jī)地球化學(xué)研究,并進(jìn)一步結(jié)合其有機(jī)巖石學(xué)特
2、征,研究討論了尚存有爭議的礦床成因。結(jié)果發(fā)現(xiàn),成礦巖系中有機(jī)質(zhì)含量豐富,有機(jī)碳含量最高可達(dá)8.3%,有機(jī)質(zhì)母質(zhì)主要來源于低等菌藻類,它們在成礦過程中發(fā)揮了重要作用:礦床形成于缺氧還原的海水環(huán)境,典型證據(jù)包括強(qiáng)烈的植烷優(yōu)勢,姥植比小于0.4,普遍檢出四環(huán)萜烷與伽馬蠟烷等;還受到熱水作用影響,典型證據(jù)包括成礦巖系具有較高的瀝青反射率,礦層比與圍巖的有機(jī)質(zhì)含量低,以及礦層干酪根同位素組成高于圍巖等。據(jù)此,提出礦床經(jīng)歷了熱水噴流與生物有機(jī)質(zhì)的共同作用,建立了成礦新模式。這些認(rèn)識還可望對其他沉積巖型礦床研究提供一定啟示。關(guān)鍵詞:重晶石礦
3、床;有機(jī)地球化學(xué);黑色巖系;早寒武世;天柱:華南中圖分類號:P593;P61文獻(xiàn)標(biāo)識碼:A文章編號:0379.1726(2014)04—0386.13OrganicgeochemistryofbaritedepositshostedintheEarlyCambrianblackshalesfromtheTianzhuCounty,GuizhouProvinceHANShan.Chu,一.HUKai。andCAOJian1.StateKeyLaboratoryforMineralDepositsResearch,Schoolof
4、EarthSciencesandEngineering,NanjingUniversity,Nanjing210023,China;2KeyLaboratoryofNuclearResourcesandEnvironment,MinistryofEducation,EastChinaInstituteofTechnology,Nanchang330013,ChinaAbstract:TheTianzhuDahebianbaritedepositsarehostedintheEarlyCambrianblackshalesofG
5、uizhouProvince,SouthChina.Theyhavethelargestreservewithinthesametypeofdepositsallovertheworld.a(chǎn)ndthusbecomeoneoftheresearchhighlightsinthisfield.Suchdepositsarerichinorganicmatter.However,lessattentionhasbeenpaidtoorganicmatterinthedeposits.Therefore,wecarryoutanorg
6、anicgeochemicalstudyin也isPaper.a(chǎn)ndfurtheraddressthedebatedoregenesiscombinedwithorganicpetrologicalcharacteristics.Theresultsshowthatthebariteore—bearingstrataarerichinorganicmatterastotalorganiccarboncontentreachesuptO8.3%.Thebio—precursorcomesmainlyfrombacteriaand
7、algae.whichhaveplayedanimportantroleonthemineralization.Thedepositwasformedinananoxicandreducingmarineenvironment.TypicalevidencesincludestrongphytaneadvantagewithPr/Ph<0.4andwidedetectionoftetracyclicterpanesandgammacerane.Ontheotherhand。theoreformationwasinfluence
8、dbyhydrotherma1water.Typicalevidencesincludehighbitumenreflectancefortheorebed,1owertotalorganiccarbon(TOC1andheavierkerogenCvaluesintheor