南秦岭柞山地区铅银锌矿成矿规律及找矿模型

南秦岭柞水银洞子—山阳桐木沟铅银锌矿带地处陕西柞山地区中部,位于中秦岭晚古生代弧前盆地的柞水—山阳矿集区内。该带东西长约71 km,南北宽1～7 km。对带内银洞子（铜）铅银菱铁矿床、黑沟铅锌菱铁矿床、桐木沟锌矿床、南沟（银）铅矿床和松林沟铅矿点的地质、矿体、蚀变、矿化规律进行总结,发现矿体均严格产于中-上泥盆统青石垭组,具有明显的时控、层控、岩控及后期热液改造成矿特征,属典型的海底热水喷流沉积-热液改造层控矿床,构成与晚古生代海底热水喷流沉积-热液改造作用有关的铅锌银成矿系列。建立以层控+热液改造为主控矿条件,以青石垭组热水沉积岩+断裂+化探异常+硫化物、重晶石、菱铁矿蚀变分带为组合的找矿模型,对柞山地区金属矿的找矿突破具有重要的指导意义。     

南图尔盖盆地Aryskum坳陷钾盐的测井响应特征及其分布

钾盐作为战略资源,在农业、工业等领域具有重要的使用价值。世界大多数固态钾资源发现于大规模的石油勘探过程中,充分利用各种油气地质、地球物理资料开展钾盐勘探对于国家发展尤为重要。位于哈萨克斯坦的南图尔盖盆地地质构造简单、资源勘探潜力较大。文中以南图尔盖盆地Aryskum坳陷为研究区块,基于其沉积地质特点,结合多口井的常规测井资料及前人研究成果,综合分析自然伽马、自然电位、三孔隙度等测井曲线的响应特征,含钾层段具体表现为自然伽马异常高值,并通过无铀伽马曲线等排除铀、钍元素影响,扩径使得中子值偏高,自然电位异常幅度由砂岩层的负异常变化为正异常,电阻率值偏高,密度值介于2.25~2.45 g/cm³,声波时差在270~350 μs/m范围内。基于含钾层测井曲线特点,利用测井曲线综合识别法、重叠法、交会图法进行研究区钾盐识别。在研究区30余口井中发现有可溶性钾盐层分布,分布在M-Ⅱ-3、M-Ⅱ-2小层底部,其中M-Ⅱ-3层底部为主要钾盐层段,并对各井含钾层段累计厚度进行统计分析。最后,借助地层对比分析含钾层段在横向和纵向上的展布情况,通过等厚图的绘制开展了找钾有利区分析,拓展了测井资料在南图尔盖盆地钾盐勘查中的应用,进而为今后研究区钾盐找矿提供重点方向。     

华南地区7-10月两类区域性极端降水事件特征及环流异常对比

利用1981—2016年7—10月中国753站逐日降水资料、气象信息综合分析处理系统（MICAPS）逐日站点降水资料、日本东京台风中心西北太平洋热带气旋（TC）最佳路径资料和NCEP/NCAR再分析资料集,分析了华南地区区域性日降水极端事件（RDPE事件）的统计特征及环流异常。根据华南地区RDPE事件的发生是否受热带气旋影响将其分为TCfree-RDPE和TCaff-RDPE两类事件,其中TCaff-RDPE事件占42%且集中发生在8月4—5候;TCfree-RDPE事件以7月发生频数最多,占其总频次的1/2以上。TCfree-RDPE事件发生时,华南地区受异常气旋性环流控制,来自西太平洋和中国南海的暖湿气流与北方冷气团在此汇合并形成一条狭长的水汽辐合带,低层辐合、高层辐散,显著强烈的上升运动为TCfree-RDPE事件的发生与维持提供了有利条件;与此同时,波扰动能量由高原东北侧及河西走廊地区向华南一带传播并在华南显著辐合,有利于华南上空扰动的发展和维持。TCaff-RDPE事件发生时,华南上空由低层到高层的斜压环流结构更为明显,异常上升运动更加强烈,热带气旋在其运动过程中携带了大量源自孟加拉湾、中国南海和西太平洋地区的水汽并输送至华南地区,水汽辐合气流更为强盛。同时,波扰动能量由高纬度地区沿河西走廊向下游传播,但在华南地区辐合不甚明显。两类极端事件发生时,加热场上的差异亦明显。华南及邻近地区上空的大气净加热及其南侧大范围区域的净冷却所形成的加热场梯度对TCfree-RDPE事件的发生有利。而TCaff-RDPE事件发生时,〈Q₁〉和〈Q₂〉在经向上由18°N以南、华南及其邻近地区、32°N以北呈负—正—负的异常分布型,正距平值更高,加热场梯度更大,有利于TCaff-RDPE事件的维持。这些结果有利于人们认识和预测华南区域性日降水极端事件的发生。      

春季对流层温度的季内和季节以上分量对南海夏季风爆发的年代际变化的相对影响

南海夏季风爆发时间在1993/1994年出现显著的年代际提早, 探讨了大气要素场的不同时间尺度分量季节演变的年代际变异对南海夏季风爆发时间的年代际变异的相对影响作用。南海夏季风爆发时间的年代际提早与南海季风区对流层经向温度梯度季节性逆转的年代际提早有密切联系。南海季风区5月中对流层经向温度梯度年代际增强主要由季风区北部温度的年代际显著增暖造成。季内分量和季节以上分量对1993年之前南海季风区经向温度梯度逆转及加强时间偏晚的作用同等重要。经向温度梯度距平的季节以上分量主要源于季风区北部温度相应分量的贡献, 而季节内分量则主要由南部相应分量影响所致, 并由25~90 d分量所主导。季节以上分量对1994年之后南海季风区经向温度梯度逆转及加强时间偏早的贡献要大于季节内分量的贡献。经向温度梯度距平的季节以上分量和季内分量对总距平的正贡献都主要来自于季风区北部温度相应分量。两种季内低频分量对温度梯度季内分量的贡献率相当, 10~25 d分量主要由南海北部温度相应分量所主导, 25~90 d分量对总距平的正贡献也源自北部分量。准双周振荡分量对各年代南海夏季风爆发具有明显的触发作用。      

南天山西段南缘断裂构造特征及对乌什凹陷发育的控制

乌什凹陷位于南天山西段以南,新生代受南天山崛起的陆内造山作用制约,与库车坳陷有相同的成盆动力学背景。因乌什凹陷南有温宿凸起阻挡了挤压应力的传播,东与库车坳陷间有北西向的构造变换带(西秋里塔格构造带)所隔,新生代变形与库车地区有不同的特征。以吉迪克组的泥岩层为滑脱面,乌什凹陷的中-新生界可分为上、下两个构造层,总体看上构造层以背冲构造为特征,下构造层则发育基底卷入的对冲构造。乌什凹陷的这一变形特征还与新生代挤压应力场自东向西迁移和走滑作用吸收了部分冲断变形有关,反映了南天山新生代构造对海西-印支期碰撞构造的继承性。文章简述了南天山造山带的构造演化,介绍了乌什凹陷周缘的主要断裂的特征,恢复了乌什凹陷中-新生代的演化并与库车坳陷进行了对比。在此基础上探讨了乌什凹陷的成盆动力学机制,分析了乌什凹陷与南天山造山带的耦合演化,指出该区的油气勘探应以三叠系为主要目的层。     

谈地下水数学模型在南干渠灌区中的预测与应用

地下水数学模型是用数学方法表述,经过概化地下水系统,在系统分析地下水补、径、排的基础上,对地下水预测分析的一种有效方法.随着南干渠灌区建成后水量的变化,本文通过选用适宜的数学模型,对灌区地下水资源量进行模拟计算,根据模拟计算结果对灌区地下水升幅进行预测,对灌区生态环境的变化做出评价.     

用树木年轮重建伊犁南天山北坡西部的降水量序列

根据采自伊犁地区南天山北坡11个采点的树木年轮样本,建立了每个采点的3种年表。通过单相关普查发现,标准化树轮年表序列与当年1~5月的降水显著相关。分析表明该时段降水与树木年轮生长呈正相关具有明确的树木生理学意义。利用新源上限(XNAUt)、昭苏上限(ZUt、ZUt 2)和特克斯下限(TLt)4个标准化树轮年表序列可较好地重建该区域在该时段的降水量。经交叉检验,所得重建方程是稳定可靠的,重建的降水序列是可信的。通过分析发现:伊犁地区南天山北坡300年以来1~5月的降水大致经历了6个偏湿阶段和6个偏干阶段;有2.0~2.8年、24.8年、28.3年、33年、99年的变化准周期;在1909年发生由多向少的突变;1740年、1870年发生由少向多的突变,其中又以1870年前后的突变最为明显。     

Early Cretaceous Metasomatized Lithospheric Mantle beneath the Central Jiangnan Orogen in South China: Geochemical and Sr-Nd Isotope Evidence from the Tuanshanbei Dolerite

It is well established that Cretaceous magmatism in the South China Block (SCB) is related to the Paleo-Pacific subduction. However, the starting time and the associated deep crust-mantle processes are still debatable. Mafic dike swarms carry important information on the deep earth (including mantle) geodynamics and geochemical evolution. In the Jiangnan Orogen (South China), there is no information on whether the Mesozoic magmatic activities in this region are also directly related to the Pacific subduction or not. In this study, we present detailed zircon U-Pb geochronological, whole-rock element and Sr-Nd isotope data for Early Cretaceous Tuanshanbei dolerite dikes, and provide new constraints on the condition of the lithospheric mantle and mantle dynamics of the SCB during that time. LA-ICP-MS zircon U-Pb dating suggests that this dolerite erupted in the Early Cretaceous (~145 Ma). All samples have alkaline geochemical affinities with K2O + Na2O = 3.11–4.04 wt%, K2O/Na2O = 0.50–0.72, and Mg# = 62.24–65.13. They are enriched in LILE but depleted in HFSE with higher initial 87Sr/86Sr ratio (0.706896–0.714743) and lower εNd(t) (?2.61 to ?1.67). They have high Nb/U, Nb/La, La/Sm and Rb/Sr, and low La/Nb, La/Ta, Ce/Pb, Ba/Rb, Tb/Yb and Gd/Yb ratios. Such geochemical signatures suggest that the fractional crystallization is obvious but crustal contamination play a negligible role during magmatic evolution. Tuanshanbei dolerite were most likely derived from low-degree (2%–5%) partial melting of a phlogopite-bearing mantle material consisted of ~85% spinel peridotite and ~15% garnet peridotite previously metasomatized by asthenosphere-derived fluids/melts with minor subduction-derived fluids/melts. Slab-rollback generally lead to the upwelling of the hot asthenosphere. The upwelling of asthenosphere consuming the lithospheric mantle by thermo-mechanical-chemical erosion. The lithospheric mantle may have partially melted due to the heating by the upwelling asthenosphere and lithospheric extension. It is inferred that the Tuanshanbei dolerite might be associated with the initial slab rollback and corresponding lithospheric extension occurred potentially at ca. 145 Ma.     

Sea level induced variations in clay mineral composition in the southwestern South China Sea over the past 17,000 yr

Variations in clay mineral composition of sediment cores from the margin and continental slope of the Sunda Shelf (southern South China Sea, SE Asia) covering the past 17,000 yr reflect changing influences of sediment sources together with clay mineral partitioning processes in shallow waters. We identify the deglacial sea level rise as the principal factor driving these changes. During the late glacial, high values of kaolinite are interpreted to reflect a higher contribution of clays from soils that have formed on the exposed Sunda Shelf and in the southern archipelagos of Indonesia. At this time core sites were located in close proximity to the mouths of the Sunda Shelf palaeo-drainage systems on the emerged shelf (“Sundaland”). The progressive landward displacement of the coastline and breakdown of these vast drainage systems during deglaciation led to a decrease in influence of the kaolinite-rich southern sources. When the coastline had retreated closely to its present-day position in mid-Holocene times, the former dominance of southern sources was replaced by a stronger influence of illite-rich sources (e.g. Borneo). The overriding control of sea level changes on the clay mineral distribution patterns precludes a definite climatic interpretation of clay mineral data in terms of climatic/monsoonal changes in such highly dynamic sedimentary environment.     

The circulation of the Indian Ocean at 32°S

Using inverse methods a circulation for a new section along 32°S in the Indian Ocean is derived with a maximum in the overturning stream function (or deep overturning) of 10.3 Sv at 3310 m. Shipboard and Lowered Acoustic Doppler Current Profiler (ADCP) data are used to inform the choice of reference level velocity for the initial geostrophic field. Our preferred solution includes a silicate constraint (−312 ± 380 kmol s⁻¹) consistent with an Indonesian throughflow of 12 Sv. The overturning changes from 12.3 Sv at 3270 m when the silicate constraint is omitted to 10.3 Sv when it is included. The deep overturning varies by only ±0.7 Sv as the silicate constraint varies from +68 to −692 kmol s⁻¹, and by ±0.3 Sv as the net flux across the section, driven by the Indonesian throughflow, varies from −7 to −17 Sv with an appropriately scaled silicate flux constraint. Thus, the overturning is insensitive to the size of the Indonesian throughflow and silicate constraint within their apriori uncertainties. We find that the use of the ADCP data adds significant detail to the horizontal circulation. These resolved circulations include the Agulhas Undercurrent, deep cyclonic gyres and deep fronts, features evidenced by long term integrators of the flow such as current meter and float measurements as well as water properties.