西昆仑山前东段新生代褶皱冲断带及其锥形楔机制

西昆仑山前东段的和田-柯克亚构造带与塔里木盆地内的麻扎塔格构造带相距为200 km,两者近似平行,遥相对应,麻扎塔格构造带是和田-柯克亚构造带的前沿,山前挤压变形量沿古近系阿尔塔什组膏泥岩向北传递约200 km到麻扎塔格,形成往北东逆冲的断层传播褶皱,在盆地腹部表现为一条显著的北西向地形隆起。因此,整个西昆仑山前东段新生代褶皱冲断带宽约为270 km,长约为220 km,由和田-柯克亚构造带、麦盖提斜坡和麻扎塔格构造带组成。中部近200 km的麦盖提斜坡内没有明显构造变形,且整个褶皱冲断带的锥形楔角度远小于活动造山带的临界锥形角,说明古近系底部阿尔塔什组膏泥岩以及新生代沉积体的形态是这个褶皱冲断带锥形楔形成的主控原因,膏泥岩控制了锥形楔的顶面坡度α基底构造形态及上覆沉积楔形体则控制了锥形楔的底部滑脱层倾角β。     

渤海湾西岸全新世地层的分段与划组

本文以岩性地层、气候地层(CaCO3含量、古温度和Rb/Sr比值等)、年代地层、沉积化学地层和生物组合地层等资料为基础,根据地层规范以及建组要求将渤海湾西岸全新世地层划分为3个组:独流镇组( Qh3 dl)、大黄洼组(Qh2dh)和西翟庄组(Qh1xz).其地层埋深界线及测年界线分别为:晚全新世独流镇组(Qh3dl)与...     

Coal resource potential of Afghanistan

abstract

Coal exploration in Afghanistan has focused exclusively on expanding the boundaries of the known Jurassic coal deposits. The systematic stratigraphic and sedimentologic studies needed to locate and characterize new prospects in other parts of the country have never been conducted. Exploration strategies are based on received wisdom formulated before tectonic theory developed, and do not incorporate current understanding of the geologic and environmental processes responsible for peat formation and burial. This analysis reassesses existing data and limited new field reconnaissance data using modern tectonic and coal geology concepts to provide a new understanding of Afghanistan’s true coal potential. Afghanistan assembled during the Phanerozoic from a minimum of 11 microcontinental fragments, 5 arc systems, 3 accretionary wedges, and 2 rift systems. An unknown number of additional Precambrian terranes with separate tectonic histories are exposed in the cores of the Phanerozoic microcontinents. All of the Phanerozoic microcontinents separated from the disintegrating Gondwanaland. Each transited equatorial latitudes prior to accreting to Asia. From a purely theoretical standpoint, peat could have accumulated on every fragment during its equatorial transit. Mississippian, Triassic, Jurassic, Cretaceous, Oligocene, and Pliocene coals and carbonaceous shales are known. Triassic, Jurassic, and Pliocene deposits have been mined, but only the economically important Jurassic outcrops have been studied to any detail. Graphite-rich Precambrian strata are common from the Mesoarchean to the Neoproterozoic, and a Neoproterozoic bone coal was encountered while drilling for copper near Kabul. Jurassic and potentially Triassic and Carboniferous coals may underlie a significant percentage of the North Afghan Platform. Jurassic coals are extremely gassy and are known hydrocarbon source rocks across most of Central Asia. In Afghanistan, where these coal systems are closer to the surface, they could be coalbed methane reservoir rocks.     

中朝古陆的解体与华北、华泰二克拉通的确立

半个世纪之前,黄汲清和任纪舜等将华北、东北南部以及西北的阿拉善这类凡有前寒武纪结晶基底出露的地区确定为单一的中朝古陆(或准地台).这种观念一直被沿用迄今.近年,构造地层地体的研究发现原称之“中朝古陆”是由华北和华泰两个克拉通构成,计 11个地块或地体.重新厘定的华北克拉通,其范围只限于辽宁省西部和北部、河北省、内蒙古南...     

加蓬海岸盆地南、北次盆成藏特征对比

加蓬海岸盆地属于被动大陆边缘盆地。盆地沉积盖层主要由白垩系、古近系和新近系组成,沉积地层组合具有明显的三分性,包括早白垩世盐下层系、早白垩世晚期阿普特期盐膏层和晚白垩世至新近纪盐上层系。根据目前的油气发现,北加蓬主要富集盐上油气资源,南加蓬主要富集盐下油气资源。从构造沉积背景、油气地质条件、油气发现规模、油气平面分布、油气勘探潜力5方面对南、北次盆进行对比,分析南、北次盆的油气聚集差异,结合勘探现状分析其勘探潜力,并指出南加蓬次盆勘探难点为圈闭识别,北加蓬次盆的勘探难点是砂体预测。     

Paleo‐fires and Atmospheric Oxygen Levels in the Latest Permian: Evidence from Maceral Compositions of Coals in Eastern Yunnan,Southern China

Inertinite maceral compositions of the Late Permian coals from three sections in the terrestrial and paralic settings of eastern Yunnan are analyzed in order to reveal the paleo-fire events and the atmospheric oxygen levels in the latest Permian. Although the macerals in the studied sections are generally dominated by vitrinite, the inertinite group makes up a considerable proportion. Its content increases upward from the beginning of the Late Permian to the coal seam near the Permian-Triassic boundary. Based on the microscopic features and the prevailing theory that inertinite is largely a by-product of paleo-fires, we suggest that the increasing upward trend of the inertinite abundance in the latest Permian could imply that the Late Permian peatland had suffered from frequent wildfires. Since ignition and burning depend on sufficient oxygen, a model-based calculation suggests that the O2 levels near the Wuchiapingian/Changhsingian boundary and the Permian-Triassic boundary are 27% and 28% respectively. This output adds supports to other discoveries made in the temporal marine and terrestrial sediments, and challenges the theories advocating hypoxia as a mechanism for the Permian-Triassic boundary crisis.     

Changes of Precipitation Infiltration Recharge in the Circumstances of Coal Mining Subsidence in the Shen‐Dong Coal Field,China

Coal mining subsidence is a universal environmental-geological problem in mining areas. By selecting the Shen-Dong coal mining subsidence area as the research field, this paper studies the changes in precipitation infiltration recharge in the circumstances of coal mining subsidence by means of field geological investigation and laboratory simulation experiments, which is expected to provide a scientific basis for eco-environmental restoration in the mining area. The results indicate that at the unstable stage of subsidence, three types of subsidence in the Shen-Dong mining area have positive effects on the precipitation infiltration recharge, and the type of full-thickness bedrock subsidence has the greatest influence. In the stable stage of subsidence, the precipitation infiltration process after long-term drought and the moisture migration in the aeration zone undergo three different stages: evaporation-infiltration before precipitation, infiltration-upward infiltration-infiltration during precipitation and evaporation-infiltration after precipitation. During a heavy rainfall infiltration process, the wetting front movement in fine sand, coarse sand and dualistic structure of fine-coarse sand consists of two stages: the stage of wetting front movement during precipitation, in which the wetting front movement distance has linear relationship with the depth, and the stage of wetting front movement after precipitation, in which the wetting front movement distance has the power function relationship with the depth. The wetting front movement velocity is influenced by the rainfall amount and the lithology in the aeration zone. However, as the depth increases, the movement velocity will decay exponentially.     

Geochemical Evidence for Coal and Carbonaceous Mudstone as the Possible Major Oil Source Rock in the Jurassic Turpan Basin,Northwest China

Petroleum geologists have debated whether the hydrocarbons from Jurassic coal measures are derived from the coals, carbonaceous mudstones or coal-measure mudstones in the Turpan Basin. Based on the geochemistry analysis of the 20 crude oils and 40 source rocks from the Turpan Basin, some data have been obtained as follows: carbon preference index and methylphenanthrene index of the Jurassic oils are 1.16–1.45 and 0.28–0.80, and the ααα C29 sterane 20S/(20S+20R) and C29 sterane ββ/(ββ+αα) are 0.44–0.51 and 0.4–0.54 respectively, which show the normal maturity of oils; the vitrinite reflectance of the source rocks from the Xishanyao to Badaowan Formations range from 0.47% to 0.97%, which indicate immature to mature thermal evolutionary stage and sufficient conditions for generating mass mature oil. The effect of hydrocarbon expulsion should be considered when studying the source of coal-derived oil by using Biomarkers. Biomarkers in the Jurassic oils from the basin are similar to those in the coals and carbonaceous mudstones, with a strong predominant content of pristane, relatively high ratio of C15/C16 sesquiterpenoids (>1), a relatively high content of low carbon number tricyclic terpanes and C24 tetracyclic terpane, little gammacerane and C29 Ts detected, an absolute predominant content of C29 sterane and a relatively high content of diasterane. However, the opposite characteristics are shown in mudstones, with an approximately equal content of pristane and phytane, relatively low ratio of C15/C16 sesquiterpenoids (<1), a relatively high content of high carbon number tricyclic terpanes and a low content of C24 tetracyclic terpane, peaks of gammacerane and C29 Ts detected obviously and an increasing C27 sterane content. All of these characteristics identify the coals and carbonaceous mudstones as the possible major oil source rocks in this area, and they were formed in the stronger oxidizing environment with shallower water than mudstones.     

瞬变电磁测深在煤炭勘查工作中的应用

目前瞬变电磁法在地质勘探中应用的越来越广。因其分辨率高,特别是横向分辨率更高,可分辨出地下规模较小的不均匀体,所以在金属矿及煤矿采空区等勘探方面应用的比较早,技术也比较成熟。笔者将瞬变电磁法用于火成岩侵入沉积地层的煤炭勘查工作中的应用效果做一介绍。     

宁夏香山含煤区找煤方向及前景探析

宁夏香山含煤区掩盖面积大,勘查程度低,空白区多。通过对已有地质资料分析,线驮石煤矿区边界断层为倾向北东的正断层,在东部土坡组露头附近有一倾向南西的正断层,两断层形成地堑使区内的含煤地层得以保存。根据矿区边界断层以西勘查资料推测,断层以东至土坡组露头区域太原组发育较稳定的中厚煤层及部分不稳定的厚煤层,煤种为无烟煤,全区可采煤层预测资源量约3．8亿t,此外在深井预测区以西大范围掩盖区也可能赋存可观的煤炭资源,如果上述两区资源量得以证实,将会改变对香山含煤区煤炭资源的评价。