Diagenesis and very low-grade metamorphism of volcaniclastic sandstones from contrasting geodynamic environments, North Island, New Zealand: the Murihiku and Waipapa terranes

Abstract The Mesozoic Murihiku and Waipapa terranes are two accretionary wedges of linked forearc and trench sediments, respectively, that were juxtaposed in the early Cretaceous.
Late Triassic to late Jurassic Murihiku terrane volcaniclastic sediments are folded into a regional syncline and have been diagenetically altered. There is a general relationship between zeolite occurrence, clay mineralogy, vitrinite reflectance and stratigraphic position. Youngest Jurassic sediments contain heulandite, analcime and stilbite, whereas late Triassic to mid-Jurassic sediments have laumontite and heulandite (in detail the zeolite distribution is complicated). Tuffaceous horizons on the eastern limb of the syncline are calcitized rather than zeolitized. Post-diagenetic fractures associated with uplift are laumontite-filled. The inferred geothermal gradient is c. 15° C km⁻¹.
The Waipapa terrane is an accretionary complex dominated by imbricated terrigenous sediments of Triassic and Jurassic age with enclosed Permian to Jurassic pelagic sediments and basalts. Late Jurassic sediments are massive volaniclastic sandstones. The sediments are non-foliated, and metamorphic minerals in the massive sandstones have crystallized in specific domains. The observed metamorphic succession of prehnite-pumpellyite and pumpellyite-actinolite facies assemblages was overprinted in the imbricated rocks during a thermal event that was late in the deformation sequence and broadly coincident with hydraulic fracturing and veining.
The metamorphic successions in the two terranes and their relationships to structural features are in excellent accord with accretionary complex models.     

利用低变质煤的有机地球化学指标探讨氧化还原作用的特征及其对成熟度评价的影响

低变质煤的有机地球化学指标,如“A”/Cor,“H”/Cor,I_H,T（max）OEP,Pr/Ph,S₁+S₂,C₃-菲/总烷基菲等随其在泥炭化过程中经受的氧化还原作用程度的变化而呈规律性变化,显示了氧化还原作用的各种特征.氧化作用以脱去一个至多个碳原子的脱羧基作用或断裂作用的形式,改变正烷烃,类异戊二烯烷烃和烷基菲的组成。并在其对残余部分性质所给予的影响的意义上,可被视为一种“超前煤化作用”。还原作用促进有机质向烃转化,随还原作用加深而发生的镜质组更加富氢的变化比镜质组数量的变化更能提高煤的产烃潜量。只有在查明了煤氧化还原程度的前提条件下,应用这些指标评价成熟度才可能更为准确。     

Microcosmic analysis of ductile shearing zones of coal seams of brittle deformation domain in superficial lithosphere

For many years, the study on ductile shearing zones mainly focuses on the strain analysis and the characteristics of microcosmic structure of felsic duc-tile shearing zones in deep layers (8—10 km). Discus-sions on the process of the development of small-type and mini-size ductile shearing zones have been re-ported in recent years[1,2]. 揇uctile deformations in brittle deformation擺3] and 揵rittle deformations in ductile deformation擺4] are rather a familiar phenome-non in nature. Researchin…     

大兴安岭北部上古生界极低级变质温度——来自碳质物拉曼光谱的证据

使用Renishaw System-1000型激光拉曼光谱仪, 研究了大兴安岭北部上古生界泥质岩石碳质物的拉曼光谱特征及其对形成温度的表征, 探讨了拉曼光谱参数与镜质体反射率(R_o)的关系。研究表明:研究区上古生界泥质岩石碳质物不具有石墨的拉曼光谱谱带吸收峰, 揭示了地层的变质程度未达到低绿片岩相。利用此次经过完善建立的拉曼光谱地质温度计, 对大兴安岭北部上古生界泥质岩石变质温度的估算结果主要为270~320℃, 表明研究区上古生界遭受了极低级变质作用, 变质程度属近变质带。依据碳质物拉曼光谱参数与镜质体反射率的相互关系, 估算研究区有机质成熟度的R_o值主要分布为3.03%~4.23%, 与实测R_o值吻合, 表明有机质演化处于过成熟阶段, 泥质岩石具有生烃的能力, 部分层位可能具有形成油气资源的潜力。     

镜质体、海相镜质体和镜质体反射率及其研究实例

镜质体是一种由高等植物木质素经过生物化学降解作用和凝胶化作用形成的胶状体,在煤和炭质泥页岩中含量高,仅出现在志留纪及其以后的地层中。此外,还有一种海相镜质体,主要由海洋低等生物(藻类、菌类及某些海洋低等动物)经腐殖化作用而形成,主要存在于早古生代及晚古生代页岩和碳酸盐岩地层中。研究表明,海相镜质体反射率(R~o_m)可作为成熟度指标加以应用。海相镜质体成熟作用轨迹不同于镜质体,二者存在一定的相关关系,使用时需把海相镜质体反射率换算为镜质体反射率(R_o)。镜质体反射率是一个寻找隐伏岩体的好方法,作者采用镜质体反射率方法对铜陵地区开展了研究,初步结果表明,铜陵地区全部数值均超过地热增温率理论曲线,说明铜陵地区深部可能有较大的隐伏岩体,深度大约在4~5 km左右。此外,在ZK113号钻孔深度200~260 m处R_o很高(2%~3%),可能预示钻孔旁侧有规模较小的隐伏侵入体,推测距钻孔距离不超过100 m,但具体方位不详。上述研究表明采用镜质体反射率方法寻找隐伏岩体是可行的,它的最大优点是解释的唯一性,R_o数值仅与温度有关,不受其他因素的干扰。     

激光荧光显微探针:方法及应用

近年来研究沉积有机物的激光诱导荧光特笥和发展基于激光的荧光显微探针技术日益受到人们的重视。采用ＦＡＭＭ－９８激光荧光显微探针研究了烃源岩显微组分。研究表明,激光荧光显微探针的微束特性使 乎可以对任何显微镜下呆辨认的有机物质颗粒进行微区分析。在激光的诱导下,所有显微组分都会产生可检测到的荧光讯号。显微组分受激光束辐照最终时刻的荧光强度（Ｆ４００）以及最终荧光强度／初始荧光强度比值（Ｆ４００／Ｆo）是     

豫西煤田构造煤反射率及其与古构造应力场的关系

为研究构造应力对煤反射率的影响,以豫西煤田不同构造区的构造煤和原生结构煤为对象,采用定向标本及反射率测定的方法作对比研究,发现构造煤的反射率比原生结构煤的反射率普遍偏高。根据反射率与构造应力的关系,求得各构造区的古构造应力场,通过与聚煤期后多次构造运动的主应力方向进行对比,可推知:影响嵩箕区二1煤变形和镜煤反射率的主要构造,是在前期断裂基础上喜山早期掀斜运动诱发的重力滑动构造,而影响崤熊区的则为燕山晚期的逆冲推覆作用。     

新疆侏罗系煤基质镜质体的岩石学特征及成烃性

运用有机岩石学和有机地球化学理论对新疆伯罗系煤中基质交易质体的岩石学特征及生烃性进行了详细研究，结果表明，基质镜质体按成因和生烃性可分成三种不同的亚型，并讨论了不同类型的基质镜质体在煤成烃作用中的意义和热演化规律。     

The Statistical Prediction of the Vitrinite Reflectance and Study of the Ancient Geothermal Field in Songliao Basin,China

The resource of the gas from coal and coal measures deep in Songliao Basin hasbeen drawing more and more attention to.It is necessary to find out the evolution regulari-ty of the geothermal field of the basin in addition to a series of geological studies in orderto predict its resources because the ancient geothermal field of the basin is one of themain factors controlling the generation,evolution and disappearance of oil and gas.Inthe recent twenty years,it is generally believed that vitrinite reflectance is the best quanti-tative marker for the ancient geothermal field.In the present paper,a systematic studyof the vitrinite reflectance value of Songliao Basin and its influence factors is made by mul-tiple statistical analysis so as to reconstruct the evolutional process of the Moho and thecorresponding geothermal field.Then,an overall prediction is made of the vitrinitereflectance and the distribution of J_3-K_1 fault basin group at the bottom of SongliaoBasin,which provides the evidence for the furth     

平庄凹陷烃源岩有机质成熟度评价

平庄凹陷盖层中发育九佛堂组、沙海组和阜新组3套烃源岩,虽然以往围绕煤矿生产展开了大量的煤田地质勘探工作,但石油、天然气勘探工作较少,研究程度较低。为了客观评价平庄凹陷的油气资源,需对烃源岩有机质成熟度进行评判。在对平庄凹陷烃源岩岩石热解、镜质组反射率、生物标志物参数分析的基础上,对平庄凹陷九佛堂组、沙海组烃源岩有机质热演化特征及演化阶段进行了系统研究。结果表明：平庄凹陷烃源岩各参数随埋藏深度的增加变化明显,具有纵向上的连续性和横向上的不均匀性;平庄洼陷烃源岩有机质成熟度处于未成熟—低成熟—成熟阶段,其中,九佛堂组烃源岩是盆地的主要成油岩系;四龙洼陷烃源岩有机质成熟度较低,对盆地成烃贡献不大。