华北地块南缘花山、五丈山岩体LA-ICP-MS锆石U-Pb年龄、地球化学特征及成因

花山复式岩体位于华北地块南缘,采用LA-ICP-MS技术测得复式岩体中的中细粒似斑状黑云二长花岗岩的锆石U-Pb年龄为128±1Ma,此年龄被解释为成岩年龄。该岩体及邻近的五丈山岩体中花岗岩具有高硅、富碱特征,为准铝-弱过铝质高钾钙碱性系列;在稀土和微量元素上,富集LREE、Rb、Ba、K、Sr等大离子亲石元素,亏损HREE、Zr、Hf、Ta、Nb、P、Ti等高场强元素,总体上Eu异常不明显,显示出I-A过渡型花岗岩的特征。锆石Lu-Hf同位素组成表明,花山花岗岩的εHf(t)主要变化于-25.8~-19.6之间,tDM2为2.81~2.43Ga,显示源区物质以古老的壳源物质为主,有年轻组分的参与。与岩体外围多金属成矿年龄的对比分析发现,外围金、钼矿床与花山复式岩体的年龄一致,比五丈山岩体晚20~25Ma,表明金、钼矿的形成与花山岩体在时空上联系密切,该岩体可能为成矿提供了热源。     

陕西西安翠华山地质景观遗迹成因探析

翠华山国家地质公园位于西安市南郊,包括水湫池、甘湫池和大坪三个景区。新的实地调查发现,甘湫池景区是一座罕见的古基岩滑坡,具有古滑坡可观察的景观形态特征,甘湫池不足堰塞湖,而是古滑坡形成的拉张洼地;水湫池堰塞坝的沉积物具有典型的“泥砾”结构,在形态特征上属于粘性重力流的碎屑流堆积;其坝体的形成与景区现有崩塌堆积无关;从空间分布和层序关系来看,景区内现有的崩塌砾石均堆积在古滑坡和泥石流堆积之上,由于各处具有不同的形态和结构特征,应具有成因的多样性和时间的多期性。     

陆相湖盆海侵事件对烃源岩发育影响机制

海侵是影响湖盆烃源岩发育的重要事件之一,通过调研国内外相关文献,述评了这一领域的研究现状。海侵事件广泛分布于中国的松辽盆地、渤海湾盆地和苏北盆地以及国外多个盆地,海侵可通过古遗迹标志、矿物岩石学标志以及地球化学特征等识别。其次海侵烃源岩一般具有有机质丰度较高、有机质类型较好的特征,主要归因于海侵事件明显促进烃源岩发育,海侵作用一方面可能为湖水带来了大量的营养物质,显著提高了古湖泊生产力,另外一方面,盐度可能有利于形成稳定的水体分层,在水底形成强还原环境,促进有机质保存。以西非裂谷盆地（Termit盆地）为例,总结了海侵影响湖相烃源岩发育的模式。     

Video cathodoluminescence microscopy of diagenetic cements and its applications

Diagenetic studies of sedimentary rocks using cold cathodoluminescence (CL) microscopy have been severely limited because of the very low intensity of visible luminescent emissions, which required long photographic exposure times, and because of the difficulty in obtaining quantitative data from CL observations. The solution to this problem is to fit the microscope with a high-sensitivity digital colour video camera linked to a computer with image enhancement and image analysis software. The new technique described in this paper:

• produces digital CL images of consistent high quality, both quickly and cheaply;

• controls the capture and editing of CL images, to reveal detailed textural information even from minerals exhibiting low level luminescence such as quartz;

• acquires quantitative information on pore systems and the abundance of cement zones from CL images.

Examples are presented to demonstrate the high quality of images produced in this way and the range of uses to which the new technique can be applied. The ability to image exactly the same field of view in both plane polarised light and CL is a particular advantage. Image analysis techniques have been developed to give a statistical characterisation of both pore systems and cement phases that infill them. The abundance of contrasting cement zones seen in CL can be measured and the abundance of cement phases can be mapped across a reservoir. The history of porosity occlusion can be reconstructed quantitatively and integrated with burial history and hydrocarbon migration. Porosity can be measured accurately and, since the technique obtains data on pore geometry as well as abundance, the pore system can be characterised by pore size distributions and pseudo-capillary pressure curves. This also opens the possibility of estimating permeability from thin sections.     

Petroleum composition in the Cuu Long Basin (Mekong Basin) offshore southern Vietnam

The Cuu Long Basin (Mekong Basin) is a rift basin off southern Vietnam, and the most important petroleum producing basin in the country. However, information on petroleum type and characteristics has hitherto been largely unavailable to the public. This paper presents petroleum geochemical data on nine oil samples from four different producing fields in the Cuu Long Basin: the Dragon (Rong), Black Lion (Sutu-Den), Sunrise (Rang ?ong) and White Tiger (Bach Ho) Fields. The oils are highly paraffinic with bimodal normal alkane distributions and show moderate pristane to phytane ratios and a conspicuous hyperbolic decrease in abundance with increasing carbon number of hopane homologues from C₃₀ to C₃₅. The TPP-index of Holba et al. (Holba, A.G., Dzou, L.I., Wood, G.D., Ellis, L., Adam, P., Schaeffer, P., Albrecht, P., Greene, T., Hughes, W.B., 2003. Application of tetracyclic polyprenoids as indicators of input from fresh–brackish water environments. Organic Geochemistry 34, 441–469) is equal to 1 in all samples which in combination with tricyclic triperpane T26/T25 ratios >1 and the n-alkane and hopane distributions mentioned above provide a strong indication of an origin from lacustrine source rocks. This is supported by the absence of marine C₃₀ desmethyl steranes (i.e. 24-n-propylcholestanes) and marine diatom-derived norcholestanes. Based on the overall biological marker distributions, the lakes probably belonged to the overfilled or balanced-fill types defined by Bohacs et al. (Bohacs, K.M., Carroll, A.R., Neal, J.E., Mankiewicz, P.J., 2000. Lake-basin type, source potential, and hydrocarbon character. An integrated sequence-stratigraphic–geochemical framework. AAPG Studies in Geology 46, 3–34). The oils were generated from source rocks at early- to mid-oil-window maturity, presumably Oligocene lacustrine shales that are present in the syn-rift succession. Oils from individual fields may, however, be distinguished by a combination of biological marker parameters, such as the oleanane index, the gammacerane index, the relative abundance of tricyclic terpanes, the proportions of diasteranes and 28-norspergulane, complemented by other parameters. The oils of the Cuu Long Basin show an overall similarity to the B-10 oil from the Song Hong Basin off northern Vietnam, but are markedly different from the seepage oils known from Dam Thi Nai on the coast of central Vietnam.     

北部湾盆地海中凹陷油气成藏条件分析

海中凹陷位于北部湾盆地西南部,其勘探程度低,对油气成藏条件欠缺系统的认识和深入的研究。以含油气系统理论为指导,在简要介绍地层与构造特征的基础上,重点论述了烃源岩、储集层、圈闭及输导介质等油气系统的基本要素,认为海中凹陷发育多套烃源岩、多套储集层、多种类型圈闭和复合的输导介质,具备油气系统形成的基本条件,具有较为广阔的油气勘探前景。     

珠江口盆地番禺4洼文昌组基于层序地层格架约束下的优质烃源岩预测

珠江口盆地番禺4洼“小而肥”,目前的探明石油地质储量已超出早期估算的地质资源量,早期对烃源岩的认识不足可能是其主要原因,尤其是对优质烃源岩的分布范围仍缺少精确刻画,在很大程度上限制了对该洼陷勘探潜力的认知。以该难点问题为切入点,利用最新钻井和地震资料,采取层序地层学开展了番禺4洼烃源岩的预测工作。通过地震资料上识别的各种反射特征,结合区内已有钻井资料识别的旋回特征,将番禺4洼文昌组划分5个三级层序,进而建立了等时地层格架。在此基础上,综合运用地震沉积学最新技术手段,精细揭示了番禺4洼文昌组文三段优质烃源岩的分布范围。研究结果表明,番禺4洼优质烃源岩分布面积较为广泛,尤其在北次洼和西次洼,优质源岩面积均超过了以往预期。这一研究成果对本区和珠江口盆地油气勘探具有一定指导意义。     

白云凹陷不同相带烃源岩地球化学特征及成藏贡献

根据烃源岩生物标志化合物、孢粉藻类组合及分析,并结合整体沉积背景,分析白云凹陷不同相带烃源岩的地球化学特征,并确定不同相带烃源岩的成藏贡献。研究表明,文昌组中深湖相烃源岩有机质丰度属于中等级别,有机质类型为Ⅱ1型,来源为藻类等水生生物,其干酪根δ13C值最轻,δ13C值<−28‰。恩平组浅湖相和文昌组浅湖相有机质均来源于陆源高等植物,干酪根δ13C值约为−27‰,有机质丰度属于中等—极好级别,有机质类型为Ⅱ2—Ⅲ型。恩平组海侵湖相烃源岩富海相沟鞭藻及三芳甲藻甾烷,干酪根δ13C值最重,约为−25‰。白云凹陷原油δ13C值主要介于−28‰～−27‰,主要来源于文昌组和恩平组的浅湖相烃源岩,原油类型的分布受沉积相带的控制,个别近洼陷的井存在文昌组中深湖相烃源岩的贡献,恩平组海侵型烃源岩对成藏几乎无贡献。     

华南沿海全新世海岸带碳酸盐胶结岩的分类及其研究意义

华南沿海的全新世海岸带碳酸盐胶结岩研究在成因、分类方面一直存有许多争议,并导致了对古海平面、构造升降、古气候等研究意义的诸多争议。本文通过成岩特征研究,将华南沿海的全新世海岸带碳酸盐胶结岩分为四类:海滩岩、砂丘岩、贝壳堤岩和硬壳灰岩,并对深圳西冲海滩岩、汕头广澳砂丘岩、韩江三角洲贝壳堤岩和海山岛硬壳灰岩等4个典型露头进行详细研究。在此基础上对这四类海岸带碳酸盐胶结岩的意义进行讨论,认为海滩岩在古海平面、海岸带演化和古气候方面具有重要研究意义,贝壳堤岩也具有古海平面(在某些条件下)和海岸线变迁的研究意义,而砂丘岩和硬壳灰岩在这些方面的研究意义较弱。     

Distribution of the organic matter in the channel-levees systems of the Congo mud-rich deep-sea fan (West Africa). Implication for deep offshore petroleum source rocks and global carbon cycle

The quantity and the source of organic matter preserved in the Recent turbiditic channel-levees systems around 4000 m-depth off the Congo River were determined using bulk geochemical approaches (Rock-Eval, elemental and isotopic analyses) as well as molecular and optical analyses on selected samples. These mud-rich sediments contain high amount of organic matter (3% Corg on average), the origin of which is a mixture of terrestrial higher-plant debris and deeply oxidized phytoplanktonic material. Although the relative contribution of continental source versus marine source of the organic matter cannot be precisely quantified, the continental fraction appears significant (at least 70–80%) especially for such depths and distances from the coast. The organic matter distribution appears very homogeneous at different scales, from the single turbiditic event to the entire levee, and changes in accumulation rates have a little impact on the quantity and quality of preserved organic matter.