Stagnant lid convection in the mid-sized icy satellites of Saturn

Thermal history models for the mid-sized saturnian satellites Mimas, Tethys, Dione, Iapetus, and Rhea have been calculated assuming stagnant lid convection in undifferentiated satellites and varying parameter values over broad ranges. Of all five satellites under consideration, only Dione, Rhea and Iapetus do show significant internal activities related to convective overturn for extended periods of time. The interiors of Mimas and Tethys do not convect or do so only for brief periods of time early in their thermal histories. Although we use lower densities than previous models, our calculations suggest higher interior temperatures but also thicker rigid shells above the convecting regions. Temperatures in the stagnant lid will allow melting of ammonia-dihydrate. Dione, Rhea and Iapetus may differentiate early and form early oceans, Iapetus only if ammonia is present. Mimas and Tethys with ammonia may differentiate if they accreted in an optically thick nebula with ambient temperatures around 250 K. Our models suggest that the outer shells of the satellites are largely primordial in composition even if the satellites differentiated. In these cases the deep interior may be layered with a pure ice shell underlain by an ammonia dihydrate layer and a rock core.     

First report of eclogites from central Tibet,China: evidence for ultradeep continental subduction prior to the Cenozoic India‐Asian collision

Eclogites characterized by a garnet + clinopyroxene + orthopyroxene + sanidine + rutile assemblage are reported for the first time in the eastern Bangong suture, central Tibet (China). Garnet and sanidine are exsolved from clinopyroxene. Al‐exchange barometer for orthopyroxene and garnet and K concentrations in clinopyroxene indicate a peak pressure of ～4 GPa. The occurrence of these ultrahigh‐pressure rocks implies the subduction of continental crust to a depth of >130 km along the eastern Bangong suture zone during the Early Jurassic. The denudation of these ultrahigh‐pressure metamorphic rocks could have provided a significant source for the Jurassic turbidites in the western Bangong ocean basin.     

不同养殖模式对鲫鱼(Carassius auratus)营养品质及特征风味的影响研究

为研究池塘内循环流水养殖与传统池塘养殖模式条件下鲫鱼的营养品质及特征风味, 对鲫鱼形体、基础营养成分、蒸煮损失和持水力、肌肉蛋白质消化率、氨基酸、脂肪酸和挥发性化合物含量等指标进行分析评价。结果表明: 跑道组和池塘组鲫鱼的形体指标和基础营养成分具有较大差异, 其中跑道组具有高蛋白低脂肪的特点。同时两种养殖模式下鲫鱼的蒸煮损失和持水力相接近。跑道组鲫鱼蛋白质消化率显著高于池塘组鲫鱼(P<0.05)。游离氨基酸分析结果表明跑道组鲫鱼中鲜味氨基酸(天冬氨酸和谷氨酸)和甜味氨基酸(谷氨酸和丙氨酸等)含量均显著高于池塘组(P<0.05), 因此跑道组鲫鱼可能具有更佳的风味。此外两种养殖模式下鲫鱼肌肉氨基酸组成无显著差异(P<0.05), 然而跑道组鲫鱼不饱和脂肪酸含量(4.803 8 g/100 g)高于池塘组(1.411 1 g/100 g)。基于GC-IMS结果可知, 两种养殖模式下鲫鱼的挥发性化合物具有显著差异。通过层次聚类热图分析从57种挥发性化合物中筛选出了33种特性差异标记物用以区分不同养殖模式下的鲫鱼。研究结果表明, 池塘内循环流水跑道养殖在一定程度上对鲫鱼营养品质和特征风味有所改善, 可以通过GC-IMS技术进行有效快速鉴别, 同时阐明了风味感官差异的物质基础, 为淡水鱼养殖模式选择和产品定位提供理论基础。     

Estimation of winter leaf area index and sky view fraction for snow modelling in boreal coniferous forests: consequences on snow mass and energy balance

Leaf area index (LAI) and canopy coverage are important parameters when modelling snow process in coniferous forests, controlling interception and transmitting radiation. Estimates of LAI and sky view factor show large variability depending on the estimation method used, and it is not clear how this is reflected in the calculated snow processes beneath the canopy. In this study, the winter LAI and sky view fraction were estimated using different optical and biomass‐based approximations in several boreal coniferous forest stands in Fennoscandia with different stand density, age and site latitude. The biomass‐based estimate of LAI derived from forest inventory data was close to the values derived from the optical measurements at most sites, suggesting that forest inventory data can be used as input to snow hydrological modelling. Heterogeneity of tree species and site fertility, as well as edge effects between different forest compartments, caused differences in the LAI estimates at some sites. A snow energy and mass balance model (SNOWPACK) was applied to detect how the differences in the estimated values of the winter LAI and sky view fraction were reflected in simulated snow processes. In the simulations, an increase in LAI and a decrease in sky view fraction changed the snow surface energy balance by decreasing shortwave radiation input and increasing longwave radiation input. Changes in LAI and sky view fraction affected directly snow accumulation through altered throughfall fraction and indirectly snowmelt through the changed surface energy balance. Changes in LAI and sky view fraction had a greater impact on mean incoming radiation beneath the canopy than on other energy fluxes. Snowmelt was affected more than snow accumulation. The effect of canopy parameters on evaporation loss from intercepted snow was comparable with the effect of variation in governing meteorological variables such as precipitation intensity and air temperature. Copyright © 2012 John Wiley & Sons, Ltd.     

大火成岩省及其在古大陆重建及裂解研究中的应用

大火成岩省是地质历史上与地球深部过程（如地幔柱）密切相关的极端地质事件,以相对较短时期内形成规模宏大的板内幔源基性岩浆活动为主要特征,对研究全球性大气—海洋环境的巨变与生物灭绝、大规模成矿及超大陆的重建和裂解均有重要意义。从潘吉亚超大陆的裂解过程可以看出,尽管不是所有的大火成岩省都与大陆裂解有关,但几乎每一次重要的裂解事件都伴有大火成岩省的出现,因此大火成岩省对于研究前潘吉亚超大陆,特别是对于缺少古生物等重建标志,古地磁数据偏少的前寒武纪超大陆重建及裂解研究有重要价值。近20多年来随着年代学技术的进步及研究工作的不断深入,大火成岩省在古大陆重建及裂解方面取得了一些重要进展,并发挥了越来越重要的作用。前寒武纪大火成岩省由于经历了多次裂解事件改造及后期抬升剥蚀或覆盖的影响,现今保留的是一些分散在不同大陆上的大火成岩省残片或碎片。用大火成岩省开展古大陆重建及裂解的目标就是通过不同陆块大火成岩省或大规模基性岩浆活动的年代学、岩石学及地球化学对比,结合其他证据,恢复大火成岩省形成时的时空分布特征,据此来确定这些陆块在超大陆中的相对或绝对位置。与其他前寒武纪大陆重建标志相似,大火成岩省也有一些局限性及不确定性,因此应用大火成岩省开展古大陆重建及裂解研究中要与前岩浆期沉积地层中的特殊事件层（如冰碛岩、火山灰、黑色页岩、不整合面、古生物等）对比、岩墙几何学产状、基性岩浆事件序列对比、古地磁、大型构造（如造山带）对比及深部地球物理等多学科方法相结合。     

应用微束分析技术研究铜钴矿床中钴的赋存状态

微束分析技术能够在微米-纳米尺度上精确分析矿石矿物的物相、形貌、结构、成分以及同位素组成,为地球科学精细研究提供重要技术支撑。本文利用多种微束分析技术的自身优势,综合运用微区X射线荧光光谱(micro-XRF)、偏光显微镜、电子探针(EPMA)以及激光剥蚀电感耦合等离子体质谱(LA-ICP-MS)分析技术,建立了一种简单直观且全面快速鉴别钴赋存状态的技术方法。首先采用偏光显微镜选出部分代表性的探针片,然后进行微区X射线荧光光谱面扫描,获得探针片中钴及组合元素分布规律及特征,再利用偏光显微镜细致观察鉴别,结合元素分布特征规律识别出独立钴矿物以及含钴矿物,最后圈出代表性矿物并采用电子探针和LA-ICP-MS进行主微量化学成分测定。将该方法应用于中非铜钴成矿带上典型铜钴矿床中钴的赋存状态研究,查明了谦比希东南矿体中的钴主要以独立矿物(钴镍黄铁矿、硫钴矿、硫铜钴矿)和类质同象(主要赋存于黄铁矿、磁黄铁矿中)两种形式存在,而谦比希西矿体中的钴主要以独立矿物——硫铜钴矿的形式零星存在。     

哈萨克斯坦主要矿产资源特征及矿业投资环境

哈萨克斯坦地处中亚核心位置,是丝绸之路经济带的重要节点和战略枢纽,具有丰富的矿产资源,地缘政治经济意义重大,是中国企业开展国际矿业投资合作的重要目标国之一。本文在系统梳理哈萨克斯坦基本国情、主要矿产资源特征及开发现状、地质工作程度和地矿管理体系等基础上,对哈萨克斯坦的矿业投资环境进行了评价,分析了矿业投资的有利和不利条件。研究认为哈萨克斯坦矿产资源禀赋优势突出,油气、铀、铬、金、钨、铅、锌及铜等矿种的资源储量居世界前列;全国仅有10%～15%的已探明矿产资源处于开发阶段,采矿业发展潜力巨大;哈萨克斯坦的总体投资环境优越,吸引外资力度逐渐加大,矿产勘探开发水平不断提升。但中国企业开展矿业投资也存在竞争力不足,以及面临政策法规不稳定、地质技术资料不可靠及运营等方面的风险。为此,建议中国投资者一方面要加强对哈萨克斯坦优势矿产的投资力度,积极拓展合作方式及合作领域;另一方面要注重与哈萨克斯坦各利益集团建立良好关系,结合企业优势,综合评价矿业项目,做好风险预警防范;同时,在投资过程中要尊重地方文化习俗,积极履行社会责任。     

Research on Roof Fracture Characteristics of Gob-Side Entry Retaining with Roof Cutting and Non-pillar Mining in Thick Coal Seam,China

Geotechnical and Geological Engineering - Based on the S1201-2 large height mining in the 2–2 coal seam of Ningtiaota colliery with on-site microseismic measurement, physical simulation and...     

冲孔灌注桩桩孔纠偏预防技术研究及应用

冲孔灌注桩虽然在各类地层都具有广泛的适用性,但是在复杂地质条件下,极易发生偏孔。结合某高层建筑冲孔灌注桩施工中频繁偏孔的情况,对冲孔过程中的偏孔问题进行全面分析研究。以桩孔纠偏预防为目标,从应对孤石和斜硬岩层2个方面来针对性进行研究,应对孤石时,合理控制钻头、冲程及冲孔频率;应对斜硬岩层时,研究了钻头增厚硬质合金块改进技术。经现场应用,有效地避免了偏孔的产生。     

不同渗透水压下完整泥页岩剪切−渗流特性研究

为了探索高压水力浸润带和消落带岩体在压剪荷载与流体入渗双因素耦合作用下剪切渗流特性的衍化规律,利用自主研发的一套新型岩石剪切−渗流耦合试验系统,对饱水泥页岩进行了常法向荷载条件下不同渗透水压的剪切−渗流耦合试验和剪切蠕变−渗流耦合试验。试验结果表明：（1）随着渗透水压力的增加,饱水泥页岩剪切强度峰值、法向变形峰值以及剪切蠕变破坏强度均有所下降,说明渗透水压力对岩样力学强度具有损伤效果。（2）在剪切−渗流耦合试验过程中,岩样剪应力与法向变形在线弹性变化的末期会出现明显的上下波动现象,并伴有水流流出,剪应力和法向变形的突变点在时间上具有一致性。（3）在剪切蠕变−渗流耦合试验过程中,水流渗出速率与渗透水压力大小呈正相关,随着剪切荷载施加等级的提高,岩样蠕变变形量增大,单位时间内累计渗出水量亦有所提升。