Influence of sedimentary environments on mechanical properties of clastic rocks

The sedimentary environments are the intrinsic factor controlling the mechanical properties of clastic rocks. Examining the relationship between rock sedimentary environments and rock mechanical properties gives a better understanding of rock deformation and failure mechanisms. In this study, more than 55 samples in coal measures were taken from seven different lithologic formations in eastern China. Using the optical microscope the sedimentary characteristics, such as components of clastic rocks and sizes of clastic grains were quantitatively tested and analyzed. The corresponding mechanical parameters were tested using the servo-controlled testing system. Different lithologic attributes in the sedimentary rocks sampled different stress–strain behaviors and failure characteristics under different confining pressures, mainly due to different compositions and textures. Results demonstrate that clastic rocks have the linear best-fit for Mohr-Coulomb failure criterion. The elastic moduli in clastic rocks are highly dependent upon confining pressures, unlike hard rocks. The envelope lines of the mechanical properties versus the contents of quartz, detritus of the grain diameter of more than 0.03 mm, and grain size in clastic rocks are given. The compressive strength or elastic modulus and the grain diameter have a non-monotonic relation and demonstrate the “grain-diameter softening” effect.     

广西环江县北山地区喷流沉积铅锌矿资源潜力及找矿方向

环江县北山地区铅锌矿均富集在同一地层层位——中上泥盆统，五圩—川山—驯乐NNE向深断裂控制着成矿带，矿床存在大量沉积成岩成矿组构，喷流沉积特征明显。其成矿地质背景、沉积相、礁硅岩套建造、同生断裂活动、赋矿层位等与邻区丹池锡一铅锌多金属矿集区类似，有巨大找矿潜力。     

黔北下寒武统黑色岩系古地温及其指示意义

采用显微光度计测定黔北下寒武统牛蹄塘组黑色岩系固体沥青反射率平均为5.89%,按相关经验公式折算出来的镜质体反射率平均为4.123%,在迈维尔图解、Karwell图解、Hood图解上投点,结合干酪根和孢粉颜色指数法,推断黑色岩系的古地温为60～250℃。结合黄铁矿热电系数法和包裹体均一法测温值,认为黑色岩系属中、低温沉积成岩成矿作用,以低温沉积成岩成矿作用为主。"热"的来源为海底火山喷溢,含矿热卤水提供了丰富的有用元素。黑色岩系有机碳含量高,属好烃源岩,有机质成熟度高,热演化程度高,属过成熟。黑色岩系古地温的研究,对阐明黑色岩系的沉积、成岩和成矿条件具有重要意义。     

Caledonian high-pressure metamorphism in the Strona-Ceneri Zone (Southern Alps of southern Switzerland and northern Italy)

The Strona-Ceneri Zone comprises a succession of polymetamorphic, pre-Alpidic basement rocks including ortho- and paragneisses, metasedimentary schists, amphibolites, and eclogites. The rock pile represents a Late Proterozoic or Palaeozoic subduction accretion complex that was intruded by Ordovician granitoids. Eclogites, which occur as lenses within the ortho-paragneiss succession and as xenoliths within the granitoids record a subduction related high-pressure event (D1) with peak metamorphic conditions of 710 ± 30 °C at 21.0 ± 2.5 kbar. After isothermal uplift, the eclogites experienced a Barrowtype (D2) tectonometamorphic overprint under amphibolite facies conditions (570-630 °C, 7-9 kbar). U-Pb dating on zircon of the eclogites gives a metamorphic age of 457 ± 5 Ma, and syn-eclogite facies rutile gives a ²⁰⁶Pb/²³⁸U age of 443 ± 19 Ma classifying the subduction as a Caledonian event. These data show that the main tectonometamorphic evolution of the Strona-Ceneri Zone most probably took place in a convergent margin scenario, in which accretion, eclogitization of MOR-basalt, polyphase (D1 and D2) deformation, anatexis and magmatism all occurred during the Ordovician. Caledonian high-pressure metamorphism, subsequent magmatism and Barrow-type metamorphism are believed to be related to subduction and collision within the northern margin of Gondwana. Editorial handling: Edwin Gnos     

鲁西寒武系凝块石特征及其形成机制的探讨

鲁西地区寒武纪地层分布广泛、出露连续,中寒武世张夏组和晚寒武世炒米店组均有凝块石产出。本文通过对该地区凝块石的野外观察和镜下鉴定,认为形成凝块石的微生物主要为附枝菌,其次是葛万菌、肾球菌和放射状菌,根据枝杈的直径大小、枝杈的细胞状分割结构及结晶程度等,附枝菌又可细分为:泥晶粗枝杈状、泥晶分段枝杈状、泥晶细枝杈状、微晶管状枝杈状和亮晶粗枝杈状。相应的群落也可划分为:泥晶树枝状、单个房室状、簇球状和亮晶树枝状。凝块石的凝块为附枝菌等蓝细菌钙化体和周围粘结的碳酸盐微粒所组成的团块,其按形态可分为:斑状、网状和树枝状。根据上述的研究,本文认为形成凝块石的理想过程可以分为4个阶段:蓝细菌的捕捉和粘结作用、蓝细菌自身钙化作用、碳酸盐的原地沉淀和沉积后作用。     

河北沧州地区第四纪地下水~(36)Cl示踪

通过对华北平原沧州地区第四纪地下水中宇宙成因核素3 6Cl进行的测定 ,其浅层咸水的3 6Cl Cl值为5 7× 10 - 1 5,证实了该区浅层地下水的盐化成因主要是蒸发浓缩所造成。该区深层地下水中大气成因的3 6Cl所占的份额为 33%～ 30 %,系由上覆咸水下移所致。     

四川叠合盆地盆山耦合特征分析

四川叠合盆地三面环山,自东而西夹持于江南、秦岭与龙门山三大山系之间,位于古亚洲、环太平洋与特提斯三大构造域的结合部位;中生代以来,先后经历了海盆、煤盆、陆相广盆、残盆四个盆地世代;盆地沉积充填过程可概括为前陆、坳陷、再生前陆三种基本样式。系统的山盆构造样式及运动学、沉积充填过程分析结果表明盆地周缘造山带造山活动期与盆内古隆起发育期时间耦合;盆地周缘造山带造山活动期与盆地沉积环境转换期时间耦合;盆地周缘造山带构造轴线走向基本保持与盆内山前坳陷或前陆褶冲带构造轴线走向相耦合;盆地周缘造山带不同时期形成的褶冲构造轴线走向基本保持与其同期盆内产生的沉积或沉降中心构造轴线走向相耦合。     

云南个旧大白岩铜锡矿床铜锡与共伴生组分赋存状态研究

位于个旧市南部的卡房矿田大白岩铜锡矿是个旧地区重要的铜矿产出地段,共伴生锡、金、银、钨、铋等有益组分。通过光薄片鉴定、电子探针测试和人工重砂分析发现,大白岩铜锡矿铜主要赋存状态为黄铜矿,其次为银黝铜矿和黝锡矿;锡主要以锡石,黝锡矿形式存在;伴生组分钨主要为白钨矿,铋元素以辉铋矿和自然铋存在,硫主要为磁黄铁矿、黄铁矿,其次为黄铜矿等硫化物,磁黄铁矿和黄铜矿中含有微量金。     

非饱和土壤水分运动参数的确定——以河南驻马店亚粘土为例

土壤水分运动参数的选取和确定是研究包气带中水分贮存和运动的基础.本文以河南驻马店亚粘土为例,进行了非饱和土壤水分运动参数的测定.通过将实测数据与经验模型拟合,将实验结果、计算结果和拟合结果进行了对比分析,发现所用的经验模型与实际数据吻合较好.研究结果表明选用的经验模型是可靠的,从而确定了土壤水分运动最优参数.     

贵州瓮福磷矿床含磷岩系沉积层序的划分

应用层序地层学的概念和方法,从沉积特征研究入手,对该区的含磷岩系——洋水组划分出5个沉积层序(旋回),结合层序界面及层序的归纳描述,确定了层序类型,并认为洋水组是一套海进体系域中由一系列低级别退积型沉积层序(旋回)组成的高级层序(Ⅰ级))。