Tracing submarine groundwater discharge flux in Tolo Harbor,Hong Kong (China)

Submarine groundwater discharge (SGD) is an important pathway for groundwater and associated chemicals to discharge to the sea. Groundwater levels monitored along a transect perpendicular to the shoreline are used to calculate SGD flux from the nearshore aquifer to Tolo Harbor, Hong Kong (China). The calculated SGD flux—recharge/discharge measured with Darcy’s Law methods—agrees well with estimates based on geo-tracer techniques and seepage meter in Tolo Harbor during previous studies. The estimated freshwater SGD is 1.69–2.0 m²/d at the study site and 0.3?±?0.04 cm/d for the whole of Tolo Harbor, which is comparable to the river discharge (0.25?±?0.07 cm/d) and precipitation (0.45?±?0.15 cm/d). The tide-driven SGD in the intertidal zone is 13.98–17.59 m²/d at the study site and 2.42?±?0.56 cm/d for the whole of Tolo Harbor. The SGD occurring in the subtidal zone and the bottom of Tolo Harbor is 3.12?±?4.63 cm/d. Fresh SGD accounts for ~5% of the total SGD, while the rest (~95%) is contributed by saline SGD driven by various forces. About 96% of the tide-driven SGD in the intertidal zone occurs in the ebbing tide period because the head difference between the groundwater level and sea level is great during this period. Tide-driven SGD in the spring tide is ~1.2 times that during neap tide. The tidal fluctuation amplitude and tide-driven SGD in the intertidal zone are positively correlated to each other; thus, a spring neap variation of the tide-driven SGD is observed.     

An insight into the surface velocity of Inylchek Glacier and its effect on Lake Merzbacher during 2006–2016 with Landsat time-series imagery

Mountain glacier is one of the extremely sensitive indicators for climate change, and its surface motion distribution and corresponding variation are valuable information for understanding ice mass exchange and glacier dynamics. This paper presents the long-term ice velocity distributions of Inylchek Glacier in the Tianshan region by pixel-tracking algorithm with time-series Landsat imagery acquired during 2006–2016. Then the monitored ice motion fields of Inylchek Glacier were carefully analyzed and revealed a generally similar spatial distribution characteristic. Most of the ice of the North Inylchek Glacier remains in a stagnant state except for the upstream part, but a relatively high velocity of 20–40 cm/day with an RMSE of 3 cm/day was observed on most part of the South Inylchek Glacier, except for the slow-moving glacier terminus. We also state the glacier dynamics around Lake Merzbacher and their possible effect on its glacier lake outburst flood (GLOF) risk. Besides, the surface velocity distribution on South Inylchek Glacier surface during the ablation period from 2014 to 2016 was also established and also compared with annual velocity. The corresponding difference yields that there is a positive relation between ice motion and temperature variation. Therefore, the time-series ice surface motion yielded by the Landsat imagery thus could provide us an efficient and low-cost way to analyze the current state and changes in glaciers, thanks to the continuous and regular spaceborne observations provided by the Landsat satellites.     

Experimental and numerical investigation on coal drawing from thick steep seam with longwall top coal caving mining

Steep coal seam mining activities will frequently occur during the next few decades in China. In this study, both experimental and numerical methods are employed to investigate the coal drawing from thick steep seam with longwall top coal caving mining. A series of analyses is performed to investigate the features of the drawing body, the distribution of top coal recovery ratio and the shape of the rock flow under steep conditions. The results indicate that the drawing body of top coal develops prior to upper side of the panel face obviously, and the top coal in the central part of the panel has a higher recovery ratio than that in the lower and upper parts in steep coal seam with caving mining method. The flow paths of the fragmented top coal are nearly straight lines moving towards the drawing window, and the fastest path maintains a constant angle with the plumb line. The spatial shape of the rock flow indicates “bidirectional asymmetry,” which results from the presence of the shield beam and dip angle of the coal seam; thus, this is the root cause of the appearance of the drawing body’s prior development towards the upper side of the panel. The field observation data indicates the same distribution of top coal recovery as that in the physical experiment and numerical simulation. Furthermore, suggested measurements are proposed to improve top coal recovery in steep seam mining based on the engineering practice of Dayuan coal mine.     

北淮阳东段山七岩体地球化学特征、LA-ICP-MS 锆石U-Pb年龄及地质意义

北淮阳东段山七岩体岩性为石英闪长岩,SiO₂、Al₂O₃含量中等,富碱质,Mg^#低,具偏铝质碱性系列岩石特征。稀土元素含量中等,La_N/Yb_N值和LREE/HREE值均较大,HREE相对于LREE明显亏损,具较弱的Ce负异常,轻稀土相对富集,分馏较明显,重稀土分馏不明显。岩石富集大离子亲石元素(LILE)Rb、Ba、K和高场强元素(HFSE)Zr、Hf、Y,明显亏损Nb、Ta、Ti、P、U。通过LA-ICP-MS锆石U-Pb定年,获得山七岩体²⁰⁶Pb/²³⁸U年龄为128.2±3.3Ma,属早白垩世早期。主量元素及微量元素地球化学特征均表明山七岩体岩浆来源于地壳,受地幔物质混染。     

柴达木盆地东部上石炭统克鲁克组碎屑岩储层特征及控制因素

柴达木盆地上石炭统克鲁克组是该区重要的古生界勘探层位,组内发育多套良好的碎屑岩层。为探究其岩石物性特征及控制因素,本次以野外露头调查为基础,利用普通薄片、铸体薄片鉴定及扫描电镜等手段,结合物性测试和压汞资料,对克鲁克组碎屑岩纵向分布规律,储层岩性、物性、孔喉特征及孔隙类型进行分析。认为克鲁克地层中克2段发育的三角洲前缘亚相和克3段的具障壁海岸潮坪相的大套含砾粗砂岩、粗砂岩砂体原生、次生孔洞发育,孔喉大、分布集中、分选好,为有利的碎屑岩储层。早成岩期压实作用、重结晶及胶结作用对克鲁克组砂岩的原生孔隙破坏严重,晚成岩期储层改造形成的溶孔、裂缝—溶孔是油气成藏的主要储存空间。该研究为预测柴东石炭系克鲁克组油气有利区域提供依据,为今后该地区的油气勘探提供理论支撑。     

克拉美丽山南缘西段盆山耦合机制

克拉美丽山位于准噶尔盆地东部,晚古生代克拉美丽洋盆向北俯冲消亡,西伯利亚板块与准噶尔地块在该地区发生碰撞造山。目前,就石炭纪之后克拉美丽山的构造活动存在持续挤压、拉分、伸展、挤压-伸展转换多种观点,构造样式也各不相同。本文应用断层相关褶皱理论,从盆山过渡带现今构造样式入手来探讨克拉美丽山南缘西段盆山耦合机制。研究结果表明,克拉美丽山西段在石炭纪之后经历了中二叠世早期、早三叠世早期、晚三叠世末期、晚侏罗世-早白垩世、晚白垩世早期和古新世末期6 次构造隆升。前4 期相对稳定沉积,晚白垩世早期,晚古生代地层沿着下二叠统底部的泥岩层滑脱面以叠瓦状构造楔样式向南楔入,构造缩短量大于15 km,现今盆山构造样式初步形成。始新世构造楔遭受后期突破断层改造。始新世后,克拉美丽山大规模的构造活动基本停止,地层遭受剥蚀最终形成现今地质结构。     

基于断层滑动数据古应力反演的影响因素及其误差分析

古构造应力场是构造动力学研究中的一个重要内容,且断层滑动数据古应力反演已经成为古构造应力场恢复研究中比较常用的重要方法之一。近年来,断层滑动数据古应力反演方法研究和应用取得了一系列重要进展,但有关反演结果的解释仍存歧义,反演结果的影响因素及其误差范围等并未得到深入研究与定量分析。本文总结指出,影响断层滑动数据古应力反演结果的主要因素包括变形体制、剪切破裂面类型、断层面的形态以及地质体内薄弱面的存在等。在此基础上,分别对新生断层和先存薄弱面滑动数据的古应力反演综合误差进行了定量分析。研究指出,在可以大致厘定变形体制或误差在允许范围内的前提下,将断层滑动数据反演结果解释为应力状态是合理可行的。各种因素导致的反演误差定量分析表明,同一期构造应力场形成的破裂面滑动数据的古应力方位反演误差最大不超过35°。换言之,在没有证据表明存在不同期次的应力作用情况下,主应力方位变化小于35° 的应力状态,可以划归同一期应力场。     

珠穆朗玛峰自然保护区湖泊动态及对区域气候变化的响应

利用Landsat卫星影像,采用面向对象分类方法提取珠穆朗玛峰自然保护区湖泊信息,分析了湖泊动态及对区域气候变化的响应关系。结果表明：（1）2015年保护区湖泊总面积为489.07 km²,构造湖、河成湖、冰川湖分别占总面积的77.3%、2.6%、20.1%。（2）1975-2015年,保护区内各类湖泊面积变化速率不同,冰川湖最大（1.05 km²·a^-1）,构造湖次之（-0.85 km²·a^-1）,河成湖最稳定（0.013 km²·a^-1）;保护区南坡冰川湖面积变化速率（0.53 km²·a^-1）略大于北坡（0.52 km²·a^-1）。（3）北坡构造湖、河成湖对区域气候的响应呈阶段性变化规律,1975-2000年珠峰地区气候呈暖湿化趋势,2000年构造湖、河成湖面积达到峰值,两类总计增加22.8 km²;2000-2015年转变为显著的暖干气候,构造湖、河成湖面积均呈减少趋势,总共减少57.16 km²。随着区域气候的变暖,冰川湖总面积不断扩大,近40年间冰川湖面积累计增加43.06 km²。（4）灰色关联度分析显示,年极端低温对构造湖面积变化影响最显著,年均气温对冰川湖起主导作用,年均相对湿度对河成湖影响最大。较其他气候因子而言,降水量对各类湖泊面积变化的影响均最小。     

俯冲带碳酸盐化对深部碳循环的启示:以中国西南天山碳酸盐化云母片岩为例

俯冲带可将地球表层碳输送至深部地幔,同时也记录着俯冲板片来源碳质流体的迁移沉淀机制,对地球深部碳循环具有重大影响。近年来,俯冲带脱碳机制的研究表明流体溶解脱碳作用是冷的大洋俯冲板片释放COH流体的重要方式,而上覆板块(尤其地幔楔)则被认为是缓冲这些COH流体的重要场所,甚至是俯冲带CO_2的唯一"归宿"。事实上,俯冲带岩石本身的固碳能力却受到了忽视,而对俯冲带岩石捕获和固存CO_2(carbon capture and storage,CCS)能力的评估对全球碳通量的估算尤为重要。本文以中国西南天山高压-超高压变质带中碳酸盐化云母片岩为例,探讨俯冲带岩石的碳酸盐化对深部碳循环的影响。西南天山长阿吾子一带的碳酸盐化云母片岩记录了俯冲板片起源的碳质流体对俯冲带云母片岩的交代作用,地球化学特征表明蛇纹岩释放的富水流体溶解俯冲洋壳中的碳酸盐可能是产生COH流体的重要机制。基于碳质流体对多硅白云母(Si(a.p.f.u.)=3.58～3.73)的交代及相对高压的碳酸盐矿物(主要为白云石和菱镁矿)与金红石的共生,结合区域上碳酸盐化云母片岩与高压碳酸盐化蛇纹岩(HP-ophidolomite)的伴生,我们认为云母片岩的碳酸盐化作用可能发生在俯冲板片峰期稍后的高压折返阶段。俯冲带云母片岩的固碳作用表明除了上覆板块,俯冲带岩石本身对于碳质流体也具有很好的吸收能力。初步估算表明俯冲带云母片岩的碳酸盐化每年可固存至少2.46～6.68Mt/yr,约占俯冲板片每年进碳量的4%～17%。