塔东北库鲁克塔格中上寒武统白云岩岩石学、地球化学特征与成因探讨——与加拿大西部盆地惠而浦(Whirlpool point)剖面对比  

The petrographic and geochemical signatures and implication of origin of the Middle and Upper Cambrian dolostone in eastern margin Tarim: Comparative studies with the Whirlpool point of the Western Canada Sedimentary Basin

作　　者：钱一雄[1] 尤东华[1] 陈代钊[2] 卿海若 何治亮[4] 马玉春[1] 田蜜[1] 席斌斌[1] 

机构地区：[1]中国石化石油勘探开发研究院无锡石油地质研究所,无锡214151 [2]中国科学院地质与地球物理研究所,北京100029 [3]University of Regina,Regina,SKS4S OA2,Canada [4]中国石化石油勘探开发研究院,北京100083

出　　处：《岩石学报》2012年第8期2525-2541,共17页Acta Petrologica Sinica

基　　金："973"项目(2005CB422100;2012CB214802);国家重大专项(2011ZX05005-002;2011ZX05008-003)联合资助

摘　　要：通过对比研究塔里木盆地东北缘库鲁克塔格隆起的乌里格孜塔格剖面与加拿大西部盆地寒武系白云岩的岩石学、地球化学及流体包裹体等特征,阐明了前者经历了三次主要白云岩(化)作用事件。①成岩早期-浅埋藏的粉细晶白云岩作用,Sr为42.75×10-6,Mn为315×10-6～506×10-6,Fe为0.2650%～0.403%;δ13CPDB=-0.47‰～-0.28‰,δ18OPDB=-7.3‰～-7.43‰,87Sr/86Sr=0.71085;平均REE=18.84×10-6,δEu平均为0.66、δCe平均为0.81,估算的形成温度分别为47.6℃和55.12℃;②中(深)埋藏的细晶及中(粗)晶白云岩化作用;Sr为56.27×10-6,Mn为312×10-6,Fe为0.13%;δ13CPDB=-1.5‰,δ18OPDB=-8.5‰,87Sr/86Sr=0.7100;REE=18.08×10-6,δEu平均为0.72、δCe平均为0.77,盐水包裹体中的均一温度平均为108.34℃,盐度变化为4%～13.7%NaCleqv;③沿裂隙或溶洞形成的粗-巨晶或鞍形的热液白云岩(石)交代充填:Sr为29.1×10-6～49.9×10-6,Mn为498×10-6～754×10-6,Fe为0.15%～1.14%;平均δ13CPDB=-0.48‰,δ18OPDB=-8.82‰,87Sr/86Sr=0.70996;平均REE=15.08×10-6,δEu平均为0.70、δCe平均为0.78;鞍形白云石中的盐水包裹体的均一温度120～150℃,盐度为5%～12%NaCleqv;溶洞中的粗-巨晶白云岩盐水包裹体的均一温度140～180℃,盐度为5%～18%NaCleqv;与西加盆地惠而浦(Whirlpoolpoint)剖面典型的热液白云岩相比较,乌里格孜塔格剖面中寒武系白云岩中缝洞中的粗-巨晶及鞍形白云石中的碳氧同位素、稀土总量、轻重稀土比均要高,但有序度、δEu、δCe、盐水包裹体形成温度及盐度相对低;因而推断它与西加盆地典型的岩浆期后热液来源不同,其流体来源于沿深部伸展走滑断裂-再循环地层热卤水,与海西晚期或燕山期-喜马拉雅期强烈挤压后弱伸展引起的二期或以上的压扭-走滑构造有关。Comparative studies fault/fracture controlled the hydrothermal dolomitization, occurred pervasively in Cambrian at the Whirlpool point outcrops, the Western Canada Sedimentary Basin, with regard to petrographic, geochemical, isotopic and fluid inclusion demonstrated that three major dolomitization events in the Middle Cambrian Moheshan Group and Upper Cambrian Tereshakeitaga Group at Wuzilitaga outcrop, Northeast Tarim basin, have been recorded. （ 1 ） Near-micritic dolostone and fine-medium crystalline dolostone, formed at low temperatures during early stages of diagenesis, similar to the replaced host rock （＂ matrix＂） in their succession and geochemical signatures; with negative value 613 CpDs （ -0.47‰--0. 28‰） and 6TM OpDB values （ -7. 3‰ - -7.43‰） as well as the lower Sr contents （42.75 × 10-6）, rather higher content of Mn （312 × 10-6 -506 × 10-6） and Fe （0. 2650% - 0. 403% ） ; 87Sr/86Sr = 0. 71085 ; REE = 18. 84 × 10-6, 6Eu = 0. 66, 6Ce = 0. 81, the estamted temperature 47.6℃ for near-micritie dolostone and 55.12℃ for fine-medium crystalline dolostone. （2） Fine-medium and medium-coarse crystalline dolostone supposed to formed during intermediate or deep burial condition, with depleted δ13C PDB （ - 1. 5‰） and δ18 O PDB （ -8. 5‰） as well as the lower Sr contents （56. 27 × 10-6）, Mn （312 × 10-6） and Fe （0. 13% ） ; with rather higher homogenization temperatures （up to 108. 34℃ at average temperature） and estimates of low and medium salinities （4% - 13.7 % NaCleqv）. （3） Fractures and rugs-lining coarse or saddle dolomite precipitation, with the lowest Sr （29. 1 × 10-6 -49. 9× 10-6）, the highest content Mn （498 × 10-6 -754 ×10-6） and Fe （0. 15% - 1.14% ）, δ13 CpDs = -- 0.48%0 and depleted 6TM OpDs = -- 8. 82%e, STSr/S6Sr = 0. 70996 ; REE = 15. 08× 10 -6, 6Eu = 0. 70, 8Ce = 0. 78 ; formed under either relatively deeper burial conditions or possibly from hydrothermal fluids, which is supported by elevated h

关 键 词：白云岩 成岩阶段 地球化学 流体包裹体 寒武系 塔里木盆地东北缘 

分 类 号：P588.245[天文地球—岩石学]