辽西地区构造演化与盆地成因类型研究

辽宁省西部地区发育了一系列中生代小型含煤盆地。这些盆地内有广泛的油气显示,但勘探效果却不理想。本文分析了辽西地区地球动力学背景,结合地球物理勘探资料研究了辽西地区盆地构造几何学和运动学特征,探讨了辽西地区构造演化史、盆地形成机制和成因类型,并以阜新盆地为例,阐述了盆地的构造特征和圈闭类型。      

卧龙湖煤矿102工作面顶板采动效应研究

基于卧龙湖煤矿的岩石力学测试资料,运用FLAC3D数值模拟软件,分析了102工作面在回采过程中的应力重分布、覆岩的变形和破坏特征。数值模拟结果表明,随着工作面的向前推进,垂直方向应力和位移成增加的趋势,采空区中间部位岩体位移近于垂直方向。研究结果为工作面布置方法、顶板支护方式的选择和采区设计提供了依据,为顶板事故的预防提供了参考资料。     

Source characteristics of the Yutian earthquake in 2008 from inversion of the co-seismic deformation field mapped by InSAR

On 21 March 2008, an Ms7.3 earthquake occurred at Yutian County, Xinjiang Uygur Autonomous Region, which is in the same year as 2008 Mw 7.9 Wenchuan earthquake. These two earthquakes both took place in the Bayar Har block, while Yutian earthquake is located in the west edge and Wenchuan earthquake is in the east. The research on source characteristics of Yutian earthquake can serve to better understand Wenchuan earthquake mechanism. We attempt to reveal the features of the causative fault of Yutian shock and its co-seismic deformation field by a sensitivity-based iterative fitting (SBIF) method. Our work is based on analysis and interpretation to high-resolution satellite (Quickbird) images as well as D-InSAR data from the satellite Envisat ASAR, in conjunction with the analysis of seismicity, focal mechanism solutions and active tectonics in this region. The result shows that the 22 km long, nearly NS trending surface rupture zone by this event lies on a range-front alluvial platform in the Qira County. It is characterized by distinct linear traces and a simple structure with 1–3 m-wide individual seams and maximum 6.5 m width of a collapse fracture. Along the rupture zone are seen many secondary fractures and fault-bounded blocks by collapse, exhibiting remarkable extension. The co-seismic deformation affected a big range 100 km × 40 km. D-InSAR analysis indicates that the interferometric deformation field is dominated by extensional faulting with a small strike-slip component. Along the causative fault, the western wall fell down and the eastern wall, that is the active unit, rose up, both with westerly vergence. The maximum subsidence displacement is ～2.6 m in the LOS, and the maximum uplift is 1.2 m. The maximum relative vertical dislocation reaches 4.1 m, which is 10 km distant from the starting rupture point to south. The 42 km-long seismogenic fault in the subsurface extends in NS direction as an arc, and it dipping angle changes from 70° near the surface to 52° at depth ～10 km. The slip on the fault plane is concentrated in the depth range 0–8 km, forming a belt of length 30 km along strike on the fault plane. There are three areas of concentrating slip, in which the largest slip is 10.5 m located at the area 10 km distant from the initial point of the rupture.     

Continual erosion of bare rocks after the Wenchuan earthquake and control strategies

The newly bared rocks created by the Wenchuan earthquake are undergoing continual intensive erosion in the form of detachment and movement of individual grains. Grain erosion is defined as the phenomenon of breaking down bare rocks under the action of insolation and temperature change, detachment of grains from the rockwalls by wind, flow down of grains on the slope under the action of gravity, and accumulation of grains at the toe of the mountain, forming a deposit fan. The Wenchuan earthquake, which occurred in Sichuan on May 12, 2008, caused thousands of avalanches and landslides and left scars on slopes and a huge area of bare rocks. Grain erosion causes flying stones, injured humans and resulted in numerous slope debris flows. The process of grain erosion and strategies to limit the erosion were studied by field investigations and field experiments. According to these field investigations and field studies, the most serious grain erosion occurs in spring and early summer when it is very dry. Rocks are broken down to grains under the action of insolation and temperature change. Then, wind blows the grains from the bare rock down slope. Experimental results showed that the amount of grains blown down by wind per area of rock surface per unit time is proportional to the fourth power of the wind speed. However, the size of the grains blown down by wind increases linearly with the wind speed. An experiment proved that grain erosion can be controlled with two moss species. Moss spores were mixed with clay suspension and splashed on bare rocks. The moss species germinated on the rock surface in one month and greened the bare rocks in two months. The moss layer protected the rocks from insolation and mitigated the effects of temperature change, thus effectively mitigated grain erosion.     

Simulation of Stress Distribution around Tunnels and Interaction between Tunnels Using an Elasto–plastic Model

This article presents a computer simulation of stress distribution around tunnels and interaction between tunnels using an elasto-plastic model. A finite element method using ANSYS software has been used for the analyses of one and two tunnels at different overburden depths with different separating distances between the tunnels. The results of numerical analyses indicate that stress distribution and stress concentration around the tunnels vary with the overburden depths. It is found that the coefficients of stress concentration for elasto-plastic medium are smaller than those for elastic one by 1.9%. Furthermore, the interaction between the two tunnels rapidly decreases with the increase of separation distance between them. In addition, for quantitatively describing the interaction between the two tunnels, a critical separation distance is introduced. The critical separation distances between the two tunnels at different overburden depths are 8 m, 12 m, and 14 m respectively. This fact is very important and essential for the design of mining tunnels and to ensure safety in tunnel engineering.     

The New Meteorite Fall of Yanzhuang—A Severely Shocked H6 Chondrite with Black Molten Materials

At 21:45 hr (Beijing time) on Oct. 31, 1990 the Yanzhuang meteorite hit the ground at the Yanzhuang village, Wenyuan County, Guangdong Province. Several fragments, totalling 3.5 kg, were recovered during the field survey. This meteorite is a rare one of its kind due to its heavily shocked features and thick veins made up of black molten materials. Olivine and low-calcium pyroxene are compositionally homogeneous with Fa=18.59, Fs=16.35 and Wo=1.29. The chemical composition (total Fe=28.0%) and recrystallized texture of the chondritic mass show that the Yanzhuang is an H6 chondrite. The black molten materials occur in the form of blocks (up to 2×3×4 cm in size) and veins (0.1–15 mm in width), and contain a lot of rounded and elliptic FeNi-FeS blobs (up to 6–10 mm in length). The metal in these blobs exhibits distinct dendritic structure characteristic of rapid cooling. Unmolten and molten samples are very similar in chemical composition, fitting well with the average H-chondrites. Partial melting and FeNi/FeS-silicate separation have not been observed in the molten materials of the Yanzhuang. This project was financially supported by the Science Foundation of Guangdong Province.     

A study on A-type granites in Suzhou,China

The Suzhou granite suite is the anorogenic product, which is located on the inactive continental margin of east China. It was emplaced about 141 Ma ago, occurring as a stock with a polygonal outline on the surface, belonging to alkali potash-feldspar granites with K₂O > Na₂O, Reit’s alkali coefficient = 0.694, SiO₂ = 74.95, and Al₂O₃/(K₂O + Na₂O)mol= 1. Besides K and Na, Li and Rb are also rather high. Highlycharged metals such as Zr, Nb, REE, Y, Sn, Th, Ga and Zn are 10, or even 50 times higher than those in the ordinary granites. Halogen elements such as F and Cl are high in abundance with F = 2700 ppm and Cl = 170 ppm on average. The abundances of deep-source elements such as Ti, Al, Ca, Mg and P are relatively low, with A1₂O₃ = 12.65% and Ca + Mg < 1%. High Ga and low Al contents are typomorphically characteristic of A type granites. Biotite in the rocks is, for the most part, annite, usually filling in quartz and feldspar crystals, indicating that the crystallization of magma proceeded under relatively anhydrous condition. More than 40 kinds of accessory minerals have been identified, of which the mantle-derived mineral chrompicotite and moissanite is of great interest. Two different intrusions, the major and supplementary intrusions, can be distinguished in the granite suite. The rock-forming temperature is estimated to be 810°C, pressure 2.5 kbars, pH 8.1,¹⁸O/¹⁶O low(δ¹⁸O_WR = 6.19‰), and_fo₂= 10⁻¹⁶. The abundances of REE are high and Eu depletion is remarkable (δEu = 0.24). A variety of mineral deposits related to the Suzhou granite suite have been recognized.     

江苏溧水马占山铜多金属矿床成矿特征及成因

马占山铜多金属矿床位于溧水盆地曹王山—爱景山多金属矿（化）带的南段,矿脉产于上侏罗统大王山组一套黑云母石英粗安岩、粗安质角砾凝灰熔岩等火山岩中,矿石类型有石英脉型黄铜矿石（金矿石）、方解石脉型黄铜矿石、石英重晶石脉型黄铜矿石、细脉型黄铜矿石、方解石脉型黄铁矿石、石英脉型黄铁矿石、石英重晶石脉型方铅矿石等。对马占山铜多金属矿床进行野外调查和室内研究结果表明：中至偏碱性的火山岩为主要成矿围岩,成矿热液与粗安岩两者可能是同一岩浆源的不同衍生物,Cu元素在研究区上、中侏罗统大王山组上段及龙王山组等火山岩中的含量明显高于地壳克拉克值,可为成矿提供物质来源;矿脉主要受控于区内近EW向构造破碎带,并与其产状一致;成矿期的石英、重晶石流体包裹体研究表明,成矿流体为无CO2的中低温低盐度NaCl-H2O流体,温度介于134～250 ℃之间,集中于200～230 ℃,盐度w（NaCl）介于0.9%～6.7%之间,集中于4%～5%;流体演化趋势为由较高温、较高盐度的流体向低温及低盐度流体演化。综上认为,马占山铜金矿床属于典型的浅成中低温热液矿床。     

青藏高原北部冰前湖沉积记录的中晚全新世冰川活动

青藏高原的冰川为亚洲地区大多数人口提供了重要的水资源,研究青藏高原的冰川活动历史有助于预估未来气候变化条件下的冰川响应。本文通过对羌塘腹地布若错沉积物岩芯的粒度、元素以及总有机碳等指标进行分析,重建了该流域中晚全新世以来的冰川活动历史。结果表明,布若错流域在5.2~4.0 cal.ka B.P.期间,冰川退缩,气候相对温暖;然而,4.0 cal.ka B.P.以来环境逐渐变干,印度季风持续减弱;随着3.2 cal.ka B.P.左右大规模的冰川前进,布若错流域进入新冰期,并受到较强西风的影响,气候寒冷干旱;1.3 cal.ka B.P.以来,流域内冰川仍然维持着较大规模,然而湖面却略有升高,可能反映了西风带来了一定的降水。此外,该流域存在4次显著的冰川前进事件,它们分别发生在3.6~3.4 cal.ka B.P.、3.2~2.3 cal.ka B.P.、1.9~1.7 cal.ka B.P.和0.4~0.1 cal.ka B.P.。这4次冷期与青藏高原其他古气候记录对应较好,这种频繁发生的冷事件可能与太阳辐射的长期衰减以及太阳活动的周期性变化有关,热带辐合带的持续南退是季风持续减弱的重要原因;此外,中晚全新世北大西洋的气候变化通过增强的西风环流对该流域产生影响。