石英脉型钨多金属矿床的扇状成矿实例及找矿模型

石英脉型钨矿床是中国数量最多的钨矿床类型,但保有储量消耗迅速,迫切需要创新找矿模型,指导找矿突破。文章结合二十余年的找矿实践,通过详细分析扇状成矿矿床实例,构建了石英脉型钨矿床新的找矿模型。该模型强调赋矿裂隙为岩浆动力成因,在花岗岩体顶部呈扇状分布型式,岩浆期后热液恰在裂隙张开时充填其中而形成扇状成矿系统;提出“就岩找矿”、“就矿找矿”、“就矿找岩”的地质、地球化学和地球物理标志,指导矿床尺度的勘查工程部署。截至目前,该模型已在广东禾尚田钨锡矿床、广西珊瑚钨锡矿床、广西社垌钨钼矿床、江西盘古山钨铋矿床等获得了验证,找矿成效显著。     

An unsplit complex frequency-shifted perfectly matched layer for second-order acoustic wave equations

The perfectly matched layer(PML) boundary condition has been proven to be effective for attenuating reflections from model boundaries during wavefield simulation. As such, it has been widely used in time-domain finite-difference wavefield simulations. The conventional PML has poor performance for near grazing incident waves and low-frequency reflections. To overcome these limitations, a more complex frequency-shifted stretch(CSF) function is introduced, which is known as the CFSPML boundary condition and can be implemented in the time domain by a recursive convolution technique(CPML). When implementing the PML technique to second-order wave equations, all the existing methods involve adding auxiliary terms and rewriting the wave equations into new second-order partial differential equations that can be simulated by the finite-difference scheme, which may affect the efficiency of numerical simulation. In this paper, we propose a relatively simple and efficient approach to implement CPML for the second-order equation system, which solves the original wave equations numerically in the stretched coordinate. The spatial derivatives in the stretched coordinate are computed by adding a correction term to the regular derivatives. Once the first-order spatial derivatives are computed, we computed the second-order spatial derivatives in a similar way; therefore, we refer to the method as two-step CPML(TS-CPML). We apply the method to the second-order acoustic wave equation and a coupled second-order pseudo-acoustic TTI wave equation. Our simulations indicate that amplitudes of reflected waves are only about half of those computed with the traditional CPML method, suggesting that the proposed approach has computational advantages and therefore can be widely used for forwarding modeling and seismic imaging.     

南黄海北部千里岩断裂活动性初探

在南黄海北部海域首次针对千里岩断裂进行了声波探测。根据声波反射剖面所显示的晚第四纪断裂活动性差异,大致以朝连岛断裂为界,可把千里岩断裂分为2段,南段晚更新世以来不活动,在日照东南海域跨断裂的声波剖面上晚更新世地层没有受到断层错断的影响;北段在晚更新世晚期活动,从千里岩岛西侧至石岛湾以东海域,在声波剖面上可见多处上更新统中上部地层错断现象。虽然自建立测震台网以来沿千里岩断裂及附近海域内尚未发生5级及以上地震,也未见小震丛集现象,但是,千里岩断裂的晚更新世活动段长度>100km,具有发生6·5级左右地震的可能性,在地震预报和地震危险性分析中值得进一步研究     

HALOE资料揭示的热带平流层CH4时空变化特征

中层大气微量成分的分布和变化是中层大气研究的重要问题之一,但是长期以来中层大气的资料非常少。卤素掩星试验（HALOE）对中层大气多种微量气体进行观测,形成中层大气多种微量元素的空间分布和时间演变资料组,这是对中层大气微量气体含量资料的极大补充。作者利用1992～2003年HALOE资料分析热带地区（20°S～20°N）平均的CH4的垂直分布和时间演变特征。结果表明:热带平流层CH4混合比在平流层下层有较充分的混合;热带平流层CH4混合比的季节变化明显,在平流层中上层以年循环为主,而在平流层下部以半年变化为主;热带平流层CH4混合比的年际变化主要有准2年和准5年振荡。       

大别-胶南高压地体变质杂岩中流体包裹体特征和形成的热动力条件

在中国陆内南北板块之间古缝合线内大别-胶南高压地体中。分布着一套变质程度不一的杂岩系,我们将其划分出三期高峰变质作用形成的不同性质变形变质岩相带,并阐述了各自所代表的矿物流体包裹体特征,计算出它们形成时的温度、压力、氧逸度、差异应力等热动力参数,为揭示地体变形变质环境和构造演化特点,提供了可靠(?)数值根据。     

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。     

深厚覆盖层高压旋喷凝结体的宏观力学参数研究

基于现有工程试验资料,通过将高压旋喷凝结体分成成芯凝结体和不成芯凝结体两组材料组成,提出了深厚覆盖层高压旋喷凝结体的统计力学模型。该模型除能反映成芯凝结体的小尺度力学性质外,还可以反映不成芯凝结体的力学性质,也可考虑试验钻孔中不同芯样获得率的影响。应用随机模拟理论,给出了大体积高喷体内成芯凝结体与不成芯凝结体的空间位置及各小尺度力学参数的抽样方法。并通过结合弹塑性有限元和随机模拟两方法,建立了高喷体宏观力学性质的计算机模拟方法。应用所提三维弹塑性有限元随机模拟方法,分析研究了向家坝水电站深厚覆盖层高压旋喷凝结体的宏观力学参数。     

持续大流量过程对黄河内蒙古河段河道塑形能力的分析与思考

2018年伏秋汛期黄河流域上游持续来水,为保证2108-2019年度黄河流域凌汛期安全,黄河流域重点水库进行了大流量持续下泄。以2018年9月的实际数据为基准,通过对重点水库实际日均出入库调度情况,内蒙古河段的重点水文站实际日均流量过程和三个年份汛期大断面套绘成果对比分析研究,可以得出水库大流量持续下泄对内蒙古河段河道塑形能力起到了关键性作用,有效的提高了主槽过流能力,河段最小平滩流量得到一定的恢复,对下一步研究黄河流域河道过流能力提供了有利的数据支撑和参考价值。     

Intrusion and its implication for subsidence: A case from the Baiyun Sag, on the northern margin of the South China Sea

We develop a series of simple numerical models to explain the anomalous subsidence and deposition phenomena on the northern continental margin of the South China Sea, in particular in the Baiyun Sag. The results suggest that a short-period high rate deposition of around 17 Ma is related to a rapid subsidence event, which may be due to episodic emplacement of a dense intrusion. Necking and gravity models indicate that in the basement of the Baiyun Sag, there is a dense zone that is 100–200 kg/m³ more dense than the surrounding country rock. Considering its high magnetic intensity and regional igneous activity, the dense zone is thought to be related to a phase of basalt intrusion that may have taken place around 17 Ma. Thermal and subsidence models indicate that a hot denser intrusion can cause significant subsidence immediately after the intrusion. The subsidence rate then slows down with cooling, thus becoming consistent with the observed subsidence curves at around 17 Ma. The results also indicate that the lithospheric strength under the Baiyun Sag is negligible, and that the high-velocity layer in the lowermost crust may be not an original part of the pre-rift crust. Instead, it is thought to be underplated intrusion emplaced at around 30 Ma when the continental margin broke up.