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1、第29卷第8期地質(zhì)通報Vo1.29.No.82010年8月GEoLoGICALBULLETINOFCHINAAug.,2010鄂爾多斯盆地上三疊統(tǒng)延長組凝灰?guī)r夾層Th元素的富集特征邱欣衛(wèi),劉池洋,毛光周,鄧煜.王飛飛QIUXin—wei,LIUChi—yang,MAOGuang—zhou,DENDYu,WANGFei—fei1.大陸動力學國家重點實驗室/西北大學含油氣盆地研究所,陜西西安710069;2.山東科技大學地質(zhì)科學與工程學院,山東青島2665101.StateKeyLaboratoryofContinentalDynamics/InstituteofPetroliferou
2、sbasinofNorthwestUniversity,Xiolz710069,Shaanx~China;2.CollegeofGeologicalScience&Engineering,ShandongUniversit)"ofScienceandTechnology,Qingdao266510.Shandon&China摘要:鄂爾多斯盆地上三疊統(tǒng)延長組凝灰?guī)r夾層分布廣泛,能譜測井資料解釋凝灰?guī)r夾層Th元素含量為25x10-35x10,元素地球化學測試結(jié)果Th含量在15×10~-80x10之間,平均366x10-6,明顯高于與其互層的泥巖或炭質(zhì)泥巖的平均值,也高于地球各圈層的平均值
3、,屬于Th富集狀態(tài)。延長組凝灰?guī)r夾層中Th的富集可能主要有2個方面的原因,其一是原始巖漿中Th含量較高,因其性質(zhì)相對不活潑,未發(fā)生明顯的遷移;其二是凝灰?guī)r經(jīng)歷了較強烈的水解蝕變作用,蝕變產(chǎn)物以粘土礦物為主,從而可能吸附了上下地層中的Th.最終導致了凝灰?guī)r夾層中Th的富集。Th的富集可以作為研究區(qū)識別凝灰?guī)r夾層的標志,有利于進行更精細的地層對比。同時,Th/U比值反映出的延長期凝灰?guī)r沉積作用所引起的元素遷移和古環(huán)境變化,可能對延長組優(yōu)質(zhì)烴源巖的發(fā)育有重要作用。關(guān)鍵詞:鄂爾多斯盆地;上三疊統(tǒng)延長組;沉積環(huán)境;凝灰?guī)r夾層;烴源巖;Th元素中圖分類號:P534.51:P595文獻標志碼:A文
4、章編號:1671—2552(2010)08—1185—07QiuXW,LiuCY,MaoGZ,DengY,WangFF.EnrichmentfeatureofthoriumelementintuffinterlayersofUpperTriassicYanchangFormationinOrdosbasin,China.GeologicalBulletinofChina,2010,29(8):1185—1191Abstract:TufinterlayersdistributewidelyinYanchangFormationofOrdosbasin.Thedataofnaturalg
5、ammaspectrometryloggingshowsthatthethoriumcontentis25×10~35×10intuflayerTheresultsofelementgeochenficaltestindicatethatthecontentofthoriumisfrom15x10to80x10,andaverageis36.6×10,whichisobviouslyhigherthantheaverageofanyotherlithospheresandtheupperandlowerlayersoftufinterlayersTherearetwofactorsm
6、aycausetheenrichmentofthoriumelementintufinterlayerofYanchangFormation.Firstly,thethoriumcontentoforiginalmagmaisveryhigh,andthegeochenfistryattributionofthoriumisin—active,sothemigrationofthoriumisrelativelynotobvious;theotherfactoristufhadexperiencedintensivealterationattheprocessofdiagenesis
7、,andtheprimaryproductsareclayminerals,whichmighthaveadsorbedthoriumelementfromupperandlowerlayers.Theenrichingcharacteristicofthoriumelementcanbeasignofrecognizingthetufinterlayerinthestudyarea,whichisfavorableformoredelicatestrat