合肥盆地三尖铺组^40Ar—^39Ar同位素年代地层学研究   总被引：8，自引：2，他引：6  

王道轩  谢宪德 《地层学杂志》2000,24(3):236-242

合肥盆地南缘中生代红层层序及时代,由于缺乏可靠的化石依据,曾几经变动人为因素很大。根据三尖铺组红层中泥炭在沉积或成岩作用条件下形成的伊利石之＾４０Ａｒ－＾３９Ａｒ定年,其坪年龄为１５７．７￣１５９．９５Ｍａ,等时线年龄为１５７．２￣１５９．９Ｍａ,并用Ｋ－Ａｒ法测年进行对比和验证,其值为１５１．８￣１５５．８Ｍａ,故确定其时代下限应为中株罗世晚期（卡洛维期）,上限可能达晚侏罗世早期（牛津期）。＾４  相似文献   

热对流成岩作用的基本特征与研究意义   总被引：18，自引：1，他引：18  

刘立  于均民  孙晓明  杨庆杰 《地球科学进展》2000,15(5):583-585

介绍了热对流产生的条件与地质背景,指出火成侵入体、盐丘和活跃断层周围等温线陡倾斜场所易发生热对流成岩作用。综述了岩浆成因热对流的岩石学记录,包括热变质作用、突然升温—逐渐降温的自生矿物组合和相对高温的自生矿物类型,分析了自生伊利石的K/Ar年龄在热对流成岩作用研究中的作用。阐述了热对流成岩作用对盆地动力学、砂岩储层和油气运移研究的意义。  相似文献   

塔里木盆地典型砂岩油气储层自生伊利石K-Ar同位素测年研究与成藏年代探讨   总被引：23，自引：1，他引：22  

张有瑜  Horst ZWINGMANN  Andrew TODD  刘可禹  罗修泉 《地学前缘》2004,11(4):637-648

塔里木盆地共发现 8套砂岩油气储层 ,对其中的 5套典型砂岩油气储层进行了自生伊利石K Ar同位素测年分析与研究。利用该项技术对其成藏史进行初步探讨是本次研究的主要目的。中央隆起下志留统沥青砂岩的自生伊利石年龄为 383.4 5～ 2 35 .17Ma ,表明志留系古油藏形成于加里东晚期—海西晚期 ;上泥盆统东河砂岩的自生伊利石年龄为 2 6 3.82～ 2 31.34Ma ,表明东河砂岩油气藏主要形成于海西晚期 ;库车坳陷依南 2气田 (依南 2井 )下侏罗统阳霞组砂岩的自生伊利石年龄为 2 8.0 8～ 2 3.85Ma ,表明油气充注发生在中新世以来 ;喀什凹陷阿克莫木气田 (阿克 1井 )下白垩统砂岩的自生伊利石年龄为 2 2 .6 0～ 18.79Ma ,表明中新世可能有古油气运移或古油藏形成 ;库车坳陷迪那 2气藏 (迪那 2 0 1井 )古近系砂岩中的伊利石主要为碎屑成因 ,不能用于进行油气成藏史研究 ,但该气藏白垩系砂岩的自生伊利石年龄为 2 5 .4 9～ 15 .4 7Ma ,表明可能为中新世成藏。本次研究表明 ,该项技术在塔里木盆地初步显示出较好的应用效果 ,具有较为广阔的应用前景。  相似文献   

田黄萝卜纹的矿物组成与成因分析     

李平 《岩石矿物学杂志》2010,29(Z1):34-37

萝卜纹是田黄的重要鉴定特征。本文通过岩石薄片、X射线衍射分析和电子探针分析等手段,确定萝卜纹的组成矿物为伊利石;萝卜纹的成因为田黄的原岩受到构造应力作用后产生了显微裂隙,次生的伊利石填充了显微裂隙;显微裂隙中的伊利石与岩石中的主要矿物迪开石光学性质差别较大而呈丝缕状(萝卜纹)。  相似文献   

Progressive,episodic deformation in the Mexican Fold–Thrust Belt (central Mexico): evidence from isotopic dating of folds and faults     

《International Geology Review》2012,54(6):734-755

We used illite Ar/Ar dating to obtain absolute ages of folds and shear zones formed within the Mexican Fold–Thrust Belt (MFTB). The methodology takes advantage of illite dating in folded, clay-bearing layers and the ability to obtain accurate ages from small-size fractions of illite using encapsulated Ar analysis. We applied our approach to a cross-section that involves folded Aptian–Cenomanian shale-bentonitic layers interbedded with carbonates of the Zimapán (ZB) and Tampico–Misantla (TMB) Cretaceous basins in central-eastern Mexico. Basinal carbonates were buried by syn-tectonic turbidites and inverted during the formation of the MFTB in the Late Cretaceous. Results from folds and shear zones record different pulses of deformation within this thin-skinned orogenic wedge.

Mineralogical compositions, variations in illite polytypes, illite crystallite size (CS), and Ar/Ar ages were obtained from several size fractions in limbs and hinges of the folds and in the shear zones. 1M_d-illite polytype (with CS of 6–9 nm) dominates in two folds in the TMB while 2M₁-illlite (with CS of 14–30 nm) dominates in the third fold, in the ZB, and in the fold/shear zone. From west (higher grade) to east (lower grade): Ar retention ages indicate shearing occurred at ~84 Ma in the westernmost shear zone, folding at ~82 Ma in the ZB with subsequent localized shearing at ~77 Ma, and Ar total gas ages constrain the time of folding at ~64 Ma on the west side of the TMB and ~44 Ma on the eastern edge. These results are consistent with the age and distribution of syn-tectonic turbidites and indicate episodic progression of deformation from west to east.  相似文献   

内蒙古林西—乌兰浩特地区二叠系极低级变质作用与生烃潜力     

李长海  李刚  王师捷  邵学峰  王颖  文恺  刘正宏 《地质力学学报》2020,26(2):271-284

极低级变质作用对年轻造山带构造演化和油气勘探有重要意义，近年来成为地质学家探讨的热点领域。文章以中国东北地区南缘石炭—二叠系为研究对象，探讨了其极低级变质作用的特征。通过对兴蒙造山带东段林西—乌兰浩特地区二叠纪地层的伊利石结晶度、b₀值和多型等参数进行测试分析发现，伊利石结晶度Kübler指数在0.175~0.47之间，大多数集中于0.25~0.35，平均值为0.30；样品b₀值主要在9.0155~9.0316 ?之间，平均值为9.0249 ?；伊利石多型主要为2M₁。以上结果表明研究区二叠系林西组和哲斯组主要经历了葡萄石-绿纤石相的极低级变质作用，变质温度200~370 ℃，压力为中压，同时表明其具有较高的生烃潜力。结合二叠系生烃期研究和区内广泛发育的白垩纪侵入体推测，二叠系极低级变质作用可能发生在早白垩世，且与岩体侵入导致的地温梯度升高有关。   相似文献   

Evaluation of 40Ar/39Ar Geochronology of Authigenic Illites in Determining Hydrocarbon Charge Timing: A Case Study from the Silurian Bituminous Sandstone Reservoirs,Tarim Basin,China     

ZHANG Youyu  LIU Keyu  and LUO Xiuquan 《《地质学报》英文版》2016,90(2):684-703

The Silurian bituminous sandstones(SBS) in the Tarim Basin, China are important basinwide reservoirs with an estimated area of approximately 249000 km2. We investigated the ages of authigenic illites in the SBS reservoirs and constrained their formation timing by using the ~(40)Ar/~(39)Ar step wise heating method. The age spectra, ~(39)Ar recoil loss and their controlling factors were investigated systematically. The ~(40)Ar/~(39)Ar ages were compared with the conventional K/Ar ages of identical clay fractions. The clay in the SBS reservoirs is dominated by orderly mixed-layer illite/smectite(I/S) with 5%–30% smectite layers. The I/S minerals morphology comprises primarily honeycomb, short filamentous and curved-lath particles, characteristic of authigenic illites. The unencapsulated ~(40)Ar/~(39)Ar total gas ages(UTGA) of the authigenic illites range from 188.56 ± 6.20 Ma to 491.86 ± 27.68 Ma, which are 7% to 103% older than the corresponding K/Ar ages of 124.87 ± 1.11 Ma to 383.45 ± 2.80 Ma, respectively. The K-Ar ages indicate multistage accumulations with distinct distribution patterns in the Tarim Basin: older(late Caledonian-early Hercynian) around the basin margin, younger(late Hercynian) in the basin centre, and the youngest(middle to late Yanshanian) in the Ha-6 well-block, central area of the North Uplift. The age difference is believed to have been caused by the ~(39)Ar recoil loss during the irradiation process. Compared with the K/Ar ages, the estimated ~(39)Ar recoil losses in this study are in the range from 7% to 51%. The ~(39)Ar recoil loss appears to increase not only with the decreasing particle sizes of the I/S, but also with increasing percentage of smectite layers(IR) of the I/S, and smectite layer content(SLC) of the samples. We conclude that due to significant ~(39)Ar recoil losses, UTGA may not offer any meaningful geological ages of the authigenic illite formation in the SBS and thus can not be used to represent the hydrocarbon charge timing. ~(39)Ar recoil losses during ~(40)Ar/~(39)Ar dating can not be neglected when dating fine authigenic illite, especially when the ordered mixed-layer I/S containing small amount of smectite layers(IR30%) in the reservoir formations. Compared with the unencapsulated Ar-Ar method, the conventional K-Ar method is less complicated, more accurate and reliable in dating authigenic illites in petroleum reservoirs.  相似文献   

Diagenesis and Very Low‐grade Metamorphism of the Upper Permian Yangjiagou Formation in Eastern Changchun,China: Evidence from Clay Mineral Geothermobarometers     

HU Daqian  ZHAN Naichen  ZHANG Jingtong  LI Yang  SUN Guosheng 《《地质学报》英文版》2018,92(3):1053-1062

The metamorphic conditions of the Upper Permian Yangjiagou Formation in eastern Changchun, China, were evaluated based on the mineral assemblage, illite crystallinity, illite polytypism,the b dimension of illite, and the chemical composition of chlorite. The pelitic rocks in the Yangjiagou Formation are characterized by illite + kaolinite + chlorite ± mixed-layer chlorite/smectite and detrital quartz + plagioclase. Illite in the formation has a crystallinity of 0.38-0.55 and comprises mixed 2 M_1 and1 M_d polytypes, indicating a metamorphic temperature of 200℃. Based on the chemical composition of chlorite and the chlorite geothermometer, we estimated diagenetic to very low-grade metamorphic conditions with temperatures of 185℃～204℃. The b dimension of illite varies from 8.992 A to 9.005 A.We used a mathematical algorithm to extend Guidotti and Sassi's(1986) diagram relating illite b dimension with temperature and pressure, and used this diagram, together with illite crystallinity and chlorite chemical composition, to semi-quantitatively estimate the formation pressure at1.2 kbar. These reveal that the Yangjiagou Formation has experienced very low-grade metamorphism.  相似文献   

Porosity preservation due to grain coating illite/smectite: Evidence from Buchan Formation (Upper Devonian) of the Ardmore Field,UK North Sea     

Longxun Tang  Jon Gluyas  Stuart Jones 《Proceedings of the Geologists' Association. Geologists' Association》2018,129(2):202-214

The Buchan Formation sandstone reservoirs from the Ardmore Field in the UK Central North Sea are fluvial-aeolian deposits and provide examples of porosity preservation in deeply-buried reservoirs (2.7–3.2?km) caused by grain-coating illite/smectite (I/S). Here, high reservoir quality commonly correlates with the occurrence of grain-coating I/S and consequent inhibition of quartz cementation in the aeolian dune and interdune sandstones. Porosity is lower in fluvial sandstones lacking grain coating I/S but with intense quartz overgrowths. We propose that the presence of I/S reflects concentration of the smectitic-rich clay bearing water which would have been the deposits of the interdune and/or distal sector of fluvial distributary system, and were introduced into aeolian deposits by mechanical infiltration. Petrographic relationships indicate that these coatings grew mainly before the mechanical compaction as the clays occur at grain contacts. The use of empirical model suggested that about 6–7% porosity have been preserved. The burial-thermal history of the Ardmore area contributed to the high quality reservoir because throughout much of the time since deposition, the Devonian sandstones have been little buried. Only from the Palaeogene the reservoir temperatures exceeded about 70?°C and rapidly buried to today’s maximum depth, which have minimized the negative effect generally ascribed to smectitic clays on reservoir quality. The circumstances of porosity preservation shown in this study may be unusual, but nonetheless have profound consequences for exploration. It is possible to identify new Buchan Formation prospects in areas hitherto dismissed because they were generally assumed to be poor reservoir.  相似文献   

Illite Crystallinity Mapping of Very Low Grade Metamorphism of Triassic Metapelites in the Zoigê Area, Western China     

TANG Yan  SANG Longkang  YUAN Yanming  YU Jishun  ZHANG Yunpeng  QI Xianmao  YANG Yunlong 《《地质学报》英文版》2012,86(1):96-105

X-ray diffraction methods for estimating the metamorphic grade of diagenetic, anchizone and epizone in metapelites are reviewed and applied to samples from a 7000?m+ borehole in western China and surface samples from the surrounding Zoigê area. Kübler’s illite crystallinity (IC) measurements provide more consistent results than calculated values of percentage of illite in the I/S mixed layers and percentage of I/S mixed layers. Down-borehole IC values display a typical burial metamorphic relationship between stratigraphic level and IC. A method for preparing very low grade metamorphic maps is described, and isograds plotted on a regional geological map at selected values of IC, delineating a high temperature diagenetic zone, an anchizone, and an epizone. The map shows that IC values are controlled by stratigraphic level in the north of the study area (i.e. burial metamorphism), and proximity to an igneous intrusive body in the south (i.e. contact metamorphism).  相似文献