青海东昆仑洪水河铁矿床新元古代含铁建造铁同位素特征及其成因意义

青海省东昆仑造山带洪水河铁矿床为一中型铁矿床,其含铁建造产于狼牙山组千枚岩中,矿石类型主要为块状磁铁石英岩型,少量为条带状磁铁石英岩型,前人一般认为其属于沉积变质型铁矿床。本文在前人研究基础上,对洪水河铁矿区含铁建造中块状铁矿石进行了铁同位素、主量元素、稀土元素和微量元素分析。结果显示：除1件样品外,其余含铁建造样品的铁同位素δ56FeIRMM014均介于0.97‰~1.97‰之间,和全球典型新元古代含铁建造的Fe同位素特征基本一致;铁矿石的SiO₂+Fe₂O₃质量分数高达78.56%~98.06%,具有极低的Al/(Al+Fe+Mn)值（0.00~0.06）,为典型的化学沉积岩;总稀土元素（w (∑REE)）变化范围为(16.49~80.89)×10^-6,没有明显的Ce异常(Ce/Ce*为0.93~1.05),轻稀土元素轻微亏损,显示出类似新元古代含铁建造型的特点。综合对比洪水河铁矿区含铁建造的Fe同位素组成、沉积时代和地球化学特征,推断洪水河铁矿区含铁建造的沉积环境为新元古代柴达木—东昆北陆块的被动大陆边缘构造环境,铁等成矿物质主要来源于海相热液流体;富含Fe²+的海相热液流体上涌并逐渐演变为低温热液后在亚氧化水体环境中与含氧海水混合,最后导致Fe²+被部分氧化并形成氢氧化铁,氢氧化铁逐渐沉积在大陆斜坡上最终形成含铁建造。洪水河铁矿的成因类型可划归为拉皮坦型新元古代含铁建造。     

Artificial Maturation of Organic Matter from Recent Venezuelan Sediments

Laboratory simulation of the catagenesis of organic matter in sedimentary rocks has been used to provide an understanding of the processes involved in petroleum generation. Several of these studies have focused on the thermal evolution of organic matter (OM) present in Recent sediments. This study examines the geochemical characteristics and experimental thermal evolution of primary organic matter from two organic facies that are thought to be major contributors to Venezuelan hydrocarbon source rocks. A third facies, generally considered unimportant for petroleum formation, is used to contrast the experimental results. Hydrous pyrolysis maturation experiments were performed for three intermediate temperatures. The products of the final 330°C stage are shown in this paper because they best illustrate the changes in the OM during catagenesis. Results from the hydrous pyrolysis experiments show that at 280°C and higher all three samples yield liquid hydrocarbons similar in composition to natural crudes and the transformed organic matter is similar to kerogen that occurs in natural source rocks. Chromatograms from the saturated fraction of extracts at 330°C are similar to natural crudes with respect to n-alkane distribution and abundance of beta; and beta;alpha; hopanes. The only difference seems to be the relative abundance of 22R over 22S isomers, which indicates immature oil. This is in contrast to indications from the R _o and T _max parameters measured on the accompanying kerogen.     

西藏冈底斯带门巴地区印支期花岗岩地球化学特征及其构造意义

门巴地区晚三叠世花岗岩主要出露在西藏冈底斯构造带的弧背断隆上,主要岩石类型为黑云角闪花岗闪长岩和黑云二长花岗岩。岩石为钙碱性,具有富SiO2、K2O的特点。K2O/Na2O平均为1.13,相对富钾。Al2O3变化于13.27%～15.53%之间,A/CNK平均为1.0,为准铝质岩石。花岗岩体稀土元素总量∑REE变化于99.5×10-6～294.72×10-6之间,轻稀土元素富集,重稀土元素亏损,具弱至中等的负Eu异常。微量元素以富K、Rb、Ba、Th等大离子亲石元素和亏损Nb、Ta、Y、Yb等高场强元素为特征。岩石学和岩石地球化学研究表明,该时代的花岗岩具I型花岗岩的特点,形成于岛弧环境,是新特提斯洋早期俯冲作用的产物。同时它也暗示着冈底斯岩浆弧带在晚三叠世就已成雏形。     

松潘-甘孜褶皱带较场弧形构造特征及其大地构造意义

根据详细野外露头特征及显微构造特征将较场弧形带由南向北分为三个变形带:弧顶部、弧核部和弧翼部,不同分带具有明显不同的变形特征。由南向北变形特征由以塑性变形为主过渡为脆性变形为主,变质流体活动喜马拉雅构造期活动强烈,且向北逐渐增强;弧核部以叠瓦状逆冲构造特征分隔弧顶和弧翼部;弧翼部东西两翼变形及变质流体活动特征具有一定差异性。较场弧形带总体体现出多期次南北向挤压—张性应力变形构造特征,叠加北西—北北西向同构造期挤压变质运动,其宏观和微观变形特征与典型走滑成因模式弧形构造特征相异,为其大地构造成因机制的解释提出了新的限制条件。     

广东省大埔县银山里铅锌银矿区成矿地质特征

银山里铅锌银多金属矿区在大地构造上隶属于华南褶皱带,地处东南沿海中生代火山岩浆活动带的南部。矿体主要赋存于下侏罗统海陆交互相碎屑岩与岩浆岩的接触带上。本文从区域成矿地质背景人手,着重研究了地层、构造、岩浆岩与成矿的关系,分析了成矿物质来源,总结了矿化富集规律,提出了找矿标志。作为一个与侵入岩浆活动有关的矿床,本文旨在通过对其成矿地质环境的深入分析,提出矿床的成矿模式,为粤东地区该类矿床的寻找提供理论上的启示。     

箕状断陷湖盆不同构造区带成岩作用特征及差异性研究:以东营凹陷沙河街组为例

东营凹陷在沙河街组沉积期为北陡南缓的箕状断陷湖盆,凹陷内可进一步细分为陡坡带、缓坡带、洼陷带及中央背斜带。在沙河街组成岩演化过程中发育了多种类型的成岩作用,主要包括压实作用、压溶作用、溶解作用、胶结作用等。不同构造区带成岩作用具有明显的差异性,具体表现为:压实作用总体表现为早期压实影响较大,后期较小,但不同构造区带差异明显;胶结作用在不同构造区带碳酸盐胶结胶物含量不同。不同粘土矿物在不同构造区带含量及转化深度不同;溶蚀作用在不同构造区带发育深度不同,从而导致次生孔隙带发育深度均明显不同。不同构造区带成岩作用的差异性导致不同构造区带成岩相带类型、特征不同。详细研究这种差异性对于寻找岩性油气藏具有重要的理论价值和实际意义。     

长江中游反向过程——来自四川盆地东部的构造地貌指示

万里长江的形成经历了数次大规模的河流袭夺事件,现今的长江中游河段(川江)曾经作为古长江的西支,自东向西汇入南流的古金沙江,后来由于不断的反向才使其与古长江的东支,即现今的长江下游得以贯通。针对这一河流演化模式,学术界普遍将长江三峡的黄陵背斜视为古长江东支和西支的分水岭,然而却一直未能获得有效的地貌证据,以致于无法解释具体的河流袭夺和反向过程。为此,本文从川东-湘鄂西弧形断褶带的构造地貌特征入手,深入分析了不同区段长江及其支流与构造线的交切关系,提出古长江东支和西支的分水岭应位于弧形带的"中线"附近的向斜谷地内,而并非前人认为的黄陵背斜。通过对向斜谷地内正交型水系样式下的河流袭夺案例分析,结合先进的河流纵剖面分析技术,揭示出由于基准面下降而造成的纵向河段被袭夺并最终反向的机制。另外,根据江汉盆地西缘(宜昌地区)的白垩纪-新生代地层的沉积学和物源分析,进一步限定了长江中游的袭夺和反向开始于始新世,直到中新世才形成现今贯通的长江。     

Advective heat transfer and fabric development in a shallow crustal intrusive granite — the case of Proterozoic Vellaturu granite,south India

Syntectonic plutons emplaced in shallow crust often contain intermediate-to low-temperature deformation microstructures but lack a high-temperature, subsolidus deformation fabric, although the relict magmatic fabric is preserved. The Proterozoic Vellaturu granite emplaced at the eastern margin of the northern Nallamalai fold belt, south India during the late phase of regional deformation has a common occurrence of intermediate-to low-temperature deformation fabric, superimposed over magmatic fabric with an internally complex pattern. But high-T subsolidus deformation microstructure and fabric are absent in this pluton. The main crystal plastic deformation and fluid enhanced reaction softening was concentrated along the margin of the granite body. Resulting granite mylonites show Y-maximum c-axis fabric in completely recrystallized quartz ribbonds, dynamic recrystallization of perthites, and myrmekite indicative of fabric development under intermediate temperature (∼ 500–400°C). The weakly-deformed interior shows myrmekite, feldspar microfracturing and limited bulging recrystallization of quartz. The abundance of prism subgrain boundaries is indicative of continuing deformation through low-temperature (∼ 300°C). The relative rates of cooling influenced by advective heat transfer and deformation of the pluton seem to control the overall subsolidus fabric development. The rapid advective heat transfer from the interior in the early stages of subsolidus cooling was followed by slow cooling through intermediate temperature window as a well-developed phyllosilicate rich mylonitic skin around the granite body slowed down conductive heat loss. Low-T crystal plastic deformation of quartz was effected at a late stage of cooling and deformation of the shallow crustal granite body emplaced within the greenschist facies Nallamlai rocks.     

湖南大地构造单元划分及其地球物理场特征

不同大地构造单元,具有不同的地球物理场特征,这些特征,显然是划分不同构造单元的准则之一。湖南大地构造分区的焦点,是江南地轴的归属问题,本文根据地震和重磁资料等,论述了它隶属于扬子准地台的合理性。指出省内两个一级构造单元的分界应在江南地轴东南缘,其南西段与传统界线一致,北东段有重大改变,应将衡阳盆地和浏阳隆起包容到江南地轴区。最后,本文突出地球物理场特征,在前人工作的基础上对我省Ⅱ、Ⅲ、Ⅳ级构造单元进行了划分。     

新疆卡拉麦里地区晚古生代以来不同构造层特征及大地构造意义

摘要：卡拉麦里地区石炭纪以来的岩石地层系统由三大套构造岩石地层单位构成, 分别是以劈理、紧闭褶皱极为发育的卡拉麦里蛇绿混杂岩带为代表的造山带基底层系,以开阔褶皱为主要构造变形的石炭纪后碰撞构造层,和高角度正断层及平缓褶皱较发育的二叠-侏罗纪陆内湖盆构造层。它们分别记录了卡拉麦里地区前石炭纪碰撞造山阶段、石炭纪后碰撞阶段和二叠纪后板内断陷 坳陷阶段的沉积 变形特征。