辽南寒武系中统缝合线类型兼论缝合线构造的成因

在辽宁南部寒武系中统徐庄组的碳酸盐岩岩石中,缝合线构造十分发育,类型齐全。其类型按缝合线构造的形态可划分为波状缝合线(包括层间缝合线和层内缝合线)、柱状缝合线、网状缝合线;按缝合线与岩层产状关系可划分为平行缝合线、斜交缝合线、垂直缝合线;按缝合线的长短和幅度可划分为大型、中型、小型和微型缝合线。缝合面凸凹不平,上、下对应的部分彼此吻合,内含许多残余不溶物质,如粘土、砂质、铁质等。沉积岩中的缝合线构造有原生和次生两种成因。原生缝合线是在地壳短暂的频繁的振荡运动的特定环境下形成的,或是在连续沉积的环境下与沉积岩的层面形成相一致的环境下形成的。次生缝合线可有非构造运动形成和构造运动形成的两类。     

论缝合线构造的地质意义

原生缝合线构造的地质意义,在于它可作为了解古地理环境的标志;在进行地层对比时可作为岩相侧变的证据;某些层间缝合线可作为划分地层沉积韵律的界线;在地质调查中,可作为判别层面的标志和用来鉴定岩层的顶和底。次生缝合线的地质意义,在于它可作为分析区域构造应力及区域构造的依据。压溶作用在形成缝合线构造的同时,岩石体积缩小,结构紧密以及缝合线内有不溶物质存在,因此原生缝合线构造不利于石油、天然气和地下水的迁移和储积。只有次生缝合线中的微缝合线才有可能成为石油、天然气和地下水的储积场所。     

塔河地区鹰山组灰岩白云石化成因及其对储层的影响

白云石化是碳酸盐典型的成岩作用类型之一,中-下奥陶统鹰山组浅海碳酸盐岩是塔河地区重要的含油气储层,普遍发育多种类型的白云石化作用。本文针对塔河地区鹰山组灰岩中沿缝合线分布这一特定类型的白云石化进行了研究。岩石学基础上的阴极发光分析、⁸⁶Sr/⁸⁷Sr比值以及δ¹³C-δ¹⁸O 的研究表明,这种类型的白云石化发育于相对还原的浅埋藏成岩环境,孔隙中的残留海水是主要的白云石化流体来源,碳酸盐矿物(主要是高镁方解石)稳定化过程中释放的Mg²⁺ 可能是白云石化主要的物质来源,而埋藏过程中逐渐升高的温度一定程度上也促进了白云石化的发生。成岩流体及Mg²⁺ 有限的供给量限制了白云石化作用的整体规模。显微结构与岩石物性分析表明,该类白云石化对储层物性参数的绝对贡献相对有限,但可能成为小规模油气运移以及深部热流体活动的潜在通道。     

Analysis of solution lineations in pebbles: Kinematical vs. dynamical approaches

Solution lineations in conglomerates, resulting from indentation of non-soluble grains of the matrix into the surface of soluble pebbles, make up a morphological and genetic continuum with gradual transition between orthogonal stylolites, oblique slickolites and parallel striations. The distributions of incidence angles of matrix grains have been analyzed in individual pebbles in order to discern their kinematical or dynamical meaning. As a general rule, they fit theoretical models of flow trajectories determined by the bulk strain (kinematical hypothesis). In contrast, they are not consistent with dynamical hypotheses based upon relationships with stress vectors. In particular, they do not fit the model of frictional sliding, which would give rise to a sharp discontinuity between slickolites parallel to the maximum principal stress σ₁ and true striations parallel to the resolved shear stress τ. Therefore, solution lineations all around a pebble cannot be considered as an analogue of multiple fault slip data, and they should not be generally analysed by methods of stress inversion based upon Bott's principle. Under certain conditions (high pebble solubility; active pressure-solution processes able to accommodate the strain rate; earlier cementation), the solution lineations tend to be parallel to each other and to the maximum shortening/compression axis. They therefore assume a double kinematical and dynanical meaning, and the deformation involves maximum volume reduction.