福建铁帽山钼矿床围岩蚀变的短波红外光谱学研究

短波红外光谱分析技术是近年来兴起并逐渐走向成熟的一种热液矿床围岩蚀变研究方法。铁帽山斑岩型钼矿床的围岩蚀变作用强烈,主要蚀变类型包括钾化、硅化、伊利石化、蒙脱石化等,并具有明显的分带性特征。其中,伊利石-蒙脱石类蚀变与斑岩型钼矿化作用密切相关。经过对钻孔岩心开展系统的短波红外光谱测量,准确地鉴定了蚀变矿物类型,划分了蚀变带,并且根据短波红外光谱测量结果计算了样品的伊利石结晶度(SWIR-IC),定量地研究了伊利石化蚀变作用的强度。结果表明,在伊利石-蒙脱石化作用范围内,伊利石结晶度越高钼矿化作用越强,但在强硅化蚀变带内,伊利石含量会有所降低,而在钾化带内,伊利石结晶度与钼矿化作用无关。在斑岩型钼矿床的找矿勘查工作中,系统地开展短波红外光谱测量,一方面可以准确鉴别蚀变矿物的类型,另一方面可以根据伊利石结晶度的指标来判断含矿热液活动中心,指导勘查工程的布设。     

哈得逊油田成藏研究

对哈得逊油田的原油成分、原油和储层沥青族组分碳同位素、储层自生伊利石年龄和包裹体研究,以及该地区沉积和构造历史的研究表明,哈得逊油田发生过两次油气充注,第一次油气充注发生在晚二叠纪,早期原油在油田范围内只是经过,并没有聚集成藏。由于当时储层埋藏较浅,储层成岩作用弱,没有包裹体的形成。晚海西期由于构造抬升,储层中残留的早期原油发生了降解,只保留了一些重质组分。目前油藏中保存下来的原油为喜马拉雅期注入的、由O2 O3源岩形成的原油。     

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

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.     

粘土矿物地温计在沉积盆地热演化研究中的应用

在成岩过程中形成的粘土矿物真实地记录了地层形成的成岩温度及其盆地热演化的信息,可以作为沉积盆地的热史指标。本文主要介绍了伊利石/蒙皂石间层矿物（以下简称伊/蒙间层或I/S间层）、伊利石结晶度、绿泥石化学成分三种常用的粘土矿物地温计的发展历史、基本原理和影响因素;回顾了我国沉积盆地热演化研究中粘土矿物地温计的应用现状,并对未来的应用推广工作提出了若干参考建议。     

胶北蓬莱群的变形与变质及其区域大地构造意义

本文通过构造与变质研究及伊利石结晶度和同位素年龄测定。分析胶北蓬莱群的变形,变质及其区域大地构造意义。作为胶北唯一盖层的蓬莱群,在晚石炭世(299±4Ma)北北东—南南西区域挤压下首次遭受了强烈的蓬莱事件变形及低绿片岩相变质。其后的后蓬莱事件在胶北地区仅造成了局部的北北东—南南西向变形构造。作为华北板块南缘的胶北带,其上的蓬莱事件是华北与扬子板块沿胶南带碰撞的结果。这表明郯庐断裂带以东这两扳块碰撞发生在晚石炭世。在秦岭—大别山碰撞带以北的华北扳块南缘,由于碰撞也出现了类似胶北带的挤压变形。     

The engineering geology of the Lower Lias Clay at Blockley,Gloucestershire, UK

Summary The Lower Lias Clay at Blockley, 20 km due south of Stratford-upon-Avon, UK, is thought to be representative of this clay formation over much of the Severn Basin. As far as the mineralogy of the clay is concerned, illite is the dominant clay mineral, kaolinite being subsidiary, with quartz, calcite, pyrite and chlorite/vermiculite present in subsidiary or accessory amounts. Weathering changes the mineralogy, with illite being degraded and calcite and pyrite being removed. Furthermore free iron oxide coatings become important as a result of weathering, with the maximum concentrations being present in the highly weathered material.The unweathered clay possesses a preferred orientation associated with turbostratic structures. At certain horizons microfolding and remoulding occurs in the unweathered clay and silty layers are displaced. Weathering has progressively destroyed the micro-structures present in the weathered clay horizons.The fissures in the Lower Lias Clay occur in five uniplanar sets. In the unweathered clay the intensity is fairly constant but it increases in a narrow zone just below the weathered horizons. The number of curved fissures also increases at this depth. This intense fissuring continues into the lowest zone of weathered clay where weathering is confined to the fissure surfaces. Fissures become less apparent in the more weathered horizons as more and more degradation has taken place. However, new smaller fissure systems are developed in the weathered clay, as are desiccation cracks.Engineering index properties and values of shear strength are given. Relationships between moisture content and strength, liquid limit and iron (Fe) content were observed, and a relationship between weathering zones and the shear strength-depth curve was established.     

砂岩储层自生伊利石40Ar-39Ar定年技术及油气成藏年龄探讨

油气成藏年龄是石油地质学和同位素年代学共同面临的科学难题之一。本文探讨砂岩储层自生伊利石40Ar-39Ar阶段加热技术获得油气成藏年龄的可能性。样品采自南海珠江口盆地第三纪珠海组砂岩储层,采用冷冻加热循环技术缓慢碎裂样品,以减少碎屑长石混入量。释出气体首先经过专门研制的纯化装置,有效地除弃有机杂质气体,然后经过2个NP10Zr/Al泵进一步纯化。06ZJ26I伊利石40Ar-39Ar激光阶段加热分析获得了阶梯状上升的年龄谱。开始3个最低激光能量阶段加权平均年龄(12.1±2.2)Ma(2σ)解释为自生伊利石的最小年龄,可能代表了油气成藏的最大年龄;而较高激光能量阶段坪年龄(98.0±0.9)Ma则代表了砂岩中陆源碎屑长石的年龄。与传统K-Ar法相比,40Ar-39Ar法可以揭示伊利石样品更多的年代学信息。     

Metamorphism of Triassic Flysch Along Profile Zoigê-Lushan, Northwest Sichuan, China

We used illite and chlorite crystallinities, index minerals, mineral assemblages, polytype and domain size of white mica, electron microprobe analysis (EMPA), b0 geobarometer and chlorite geothermometer to quantify the diagenetic and metamorphic overprint on the Triassic flysch formations in the Songpan-Garzê orogen along profile Zoigê-Lushan, northwest Sichuan. Two anchizones, two epizones, one diagenetic zone and a transition belt in-between them are defined on the basis of the obtained data. lllite crystallinity correlates strongly with the best mean domain size of mica and moderately with chlorite crystallinity. 2M1 white mica polytype are observed within the epizone whilst 2M1 and 1M polytypes occur in the anchizone and diagenetic zone. Epizonal metamorphism reached maximum temperatures of 370℃±21℃ at low-to intermediate pressure conditions. Clay minerals underwent Ostwaid ripening during metamorphism. Rocks from both sides of the Longmenshan fault reveal contrasting degrees of metamorphic overprint: on the northwest side of the Longmenshan fault, epimetamorphlc conditions contrast with diagenetic rocks on the southeast side.     

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

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。      

Progressive sequence of reactions of the Ryoke metamorphism in the Yanai district, southwest Japan: the formation of cordierite

The compositions of biotite and muscovite were examined in terms of the paragenesis and the metamorphic grade in low- to medium-grade pelitic rocks of the Ryoke metamorphism in the Yanai district, southwest Japan. The biotite and muscovite that coexist with K-feldspar have a higher K component in an A'KF diagram than those in rocks lacking K-feldspar. This fact reflects an increase in the K₂O content in muscovite, but in biotite it reflects an increase of not only the K₂O content but also of the octahedral vacancy.
At higher metamorphic grade beyond the cordierite isograd, where cordierite coexists with neither chlorite nor K-feldspar, the biotite shows an increase in illite, K Aliv □xii−1 Si−1, and Tschermak components, Alvi Aliv R+−1 Si−1, where □xii and R+ denote the interlayer vacancy and (Fe+Mg+Mn), respectively. A reaction to define the cordierite isograd is proposed by treating this chemical change as being responsible for the first appearance of cordierite, i.e. K,Al-poor biotite+phengitic muscovite=K,Al-rich biotite+cordierite+quartz+water .By treating this as a key reaction in medium-grade metamorphism, a set of reaction in a progressive metamorphism is established for the Ryoke metamorphism, a typical low-pressure type metamorphism. Some textures in one of the high-grade areas, the K-feldspar-cordierite zone, suggest that a further two prograde reactions have taken place, i.e. andalusite+biotite+quartz=cordierite+K-feldspar+water
and   andalusite=sillimanite.quartz=cordierite+K-feldspar+water
This implies that this zone probably has a P–T  path involving isobaric heating.