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1、2014年3月,第20卷,第1期,139—150頁高校地質(zhì)學(xué)報March2014,Vo1.20,No.1,pp.139—150GeologicalJournalofChinaUniversities鄂爾多斯盆地二疊紀(jì)石盒子組沉積期南部沉積邊界探討羅婷婷,周立發(fā)大陸動力學(xué)國家重點實驗室西北大學(xué)地質(zhì)學(xué)系,西安710069摘要:為了確定石盒子組沉積期鄂爾多斯盆地的南部邊界,在大量野外露頭觀測及實驗測試基礎(chǔ)上,通過巖石學(xué)對比及物源綜合分析,對鄂爾多斯盆地南緣和北秦嶺地區(qū)石盒子組物源區(qū)的構(gòu)造屬性進(jìn)行了研究,并對物源區(qū)進(jìn)行了
2、分析與對比。研究結(jié)果表明:所研究兩個地區(qū)的石盒子組的巖屑組成相似,均以淺變質(zhì)巖、花崗巖為主,含少量構(gòu)造巖;砂巖碎屑成分相似,都與來源于再循環(huán)造山帶源區(qū)中的碰撞造山帶與前陸隆起物源區(qū)相關(guān);并且在SiOJAlO,一K20/NaO和K20/N%0一SiO:及Zr-Th,La—Th—Sc,Th—Sc—Zr/10構(gòu)造環(huán)境判別圖解中兩研究區(qū)物源區(qū)的構(gòu)造環(huán)境基本一致,F(xiàn)l—F2判別圖顯示物源區(qū)一致,并且稀土元素配分模式相似。北秦嶺元古界的變質(zhì)巖、巖漿巖及其以南地區(qū)的再循環(huán)造山帶中的低級變質(zhì)的沉積巖可能為鄂爾多斯盆地南緣和北秦嶺
3、地區(qū)石盒子組砂巖碎屑的主要風(fēng)化母巖。結(jié)合構(gòu)造環(huán)境分析認(rèn)為,在石盒子組沉積期,鄂爾多斯盆地的南部邊界可能已經(jīng)越過洛南斷裂,達(dá)到北秦嶺及其更南的區(qū)域。關(guān)鍵詞:鄂爾多斯盆地;石盒子組;物源區(qū);二疊紀(jì).一中圖分類號:P618.130.2文獻(xiàn)標(biāo)識碼:A文章編號:1006—7493(2014)01—0139—12DiscussionontheSouthernBoundaryofthePermianShiheziFormationintheOrdosBasinLUOTingting,ZHOULifaStateKeylabora
4、toryofContinentalDynamicsDepartmentofGeology,NorthwestUniversity,Xi’an710069,ChinaAbstract:TheaimofthispaperiStodiscusstheoriginalsouthernboundaryofthePermianShiheziFormationinthe0rdOSBasin.Basedonfieldobservationandlaboratoryworks,throughpetrologicalandprove
5、nanceanalyses,thispaperdiscussesitsprovenanceandtectonicaffinityoftheShiheziFormationinsouthernOrdosBasinandNorthQinling.TheresultssuggestthatrocklithicsoftheShiheziFormationfrombothareasaresimilarandischaracterizedbyepimetamorphicrockandgranite,withfewtecton
6、ite;thedetritalmodecompositionsgeesimilarandbothareassociatedwithcollisionalorogenicbeltandforelandupliftprovenance;InSiO2/Al2O3一K2OfNa20andK2O/Na20-SiO2,Z卜Th,La-Th-Sc,andTh-Sc-Zr/10diagrams,bothareasshowthesametectonicbackground.F1一F2distinguishdiagramshowst
7、heconsistentprovenanceofthesetwoareas.TheyalsohavesimilarREEdistributionpatterns.Therefore,metamorphicrockandmagmaticrockinProterozoicofNorthQinlingaswellasthelow‘grademetamorphicrocksofrecycledorogentoitssouthernareamaymostprobablythepotentialsourcesfortheSh
8、iheziFormationinsouthernOrdosBasinandNorthQinling.ItisinferredthatthesouthborderoftheOrdosBasinhadcrossedLuonantectonicbeltandmaybereachedtoNorthQinling.Keywords:OrdosBasin;ShiheziFormati