Paleoearthquakes in the Uimon basin (Gorny Altai)

Paleoseismological studies confirm that the Uimon basin is thrust by its northern mountain border along the active South Terekta fault. The latest motion along the fault in the 7-8th centuries AD induced an earthquake with a magnitude of M_w= 7.4-7.7 and a shaking intensity of I = 9-11 on the MSK-64 scale. The same fault generated another event (M > 7, I = 9-10), possibly, about 16 kyr ago, which triggered gravity sliding. The rockslide dammed the Uimon valley and produced a lake, where lacustrine deposition began about 14 ± 1 kyr ago, and a later M > 7 (I = 9-10) earthquake at ~ 6 ka caused the dam collapse and the lake drainage. Traces of much older earthquakes that occurred within the Uimon basin are detectable from secondary deformation structures (seismites) in soft sediments deposited during the drainage of a Late Pleistocene ice-dammed lake between 100 and 90 ka and in ~ 77 ka alluvium. The magnitude and intensity of these paleoearthquakes were at least M > 5.0-5.5 and I > 6-7.     

新特提斯洋俯冲起始的地质记录:土耳其南部蛇绿岩和变质底板

在现行板块构造理论的框架下,板块的初始俯冲是岩浆活动和构造运动发生转变的重要过程,亦是理解板块运动的关键节点。在俯冲起始过程中,主要存在四个方面的地质记录,分别为一系列地球化学成分多样的岩浆活动、SSZ型蛇绿岩、变质底板和玻安岩及其对应的铬铁矿床。特提斯造山带作为公认的研究板块构造理论尤其是初始俯冲的关键场所,一直备受地学界的重视。而土耳其南部构造带作为特提斯造山带的重要组成部分,亦是确定亚欧板块和阿拉伯板块之间缝合线存在的重要标志。该南部构造带是研究新特提斯洋俯冲起始的理想场所,上述关于俯冲初始的四个地质记录均保存良好,且有如下方面的重要特点:1)不同地区的镁铁质岩石甚至同一地区的镁铁质岩石具有不同的地球化学特征,从似洋中脊玄武岩,到过渡型岩石类型和玻安质岩石均有发育; 2)大部分蛇绿岩具有完整的序列,各单元及变质底板岩石中普遍发育侵入的基性岩脉,产状多变,是多期岩浆事件的产物; 3)蛇绿岩下部通常发育一套角闪岩相变质底板,且其年龄与蛇绿岩的形成年龄基本一致; 4)蛇绿岩中普遍发育铬铁矿床,以高Cr型为主,部分蛇绿岩中还赋存高Al-高Cr的过渡型铬铁矿,均被认为是幔源岩浆与地幔橄榄岩反应的产物。因而,这些地质体完整记录了新特提斯洋形成-俯冲-消减的演化过程。     

Geological Controls on the CBM Productivity of No.15 Coal Seam of Carboniferous–Permian Taiyuan Formation in Southern Qinshui Basin and Prediction for CBM High-yield Potential Regions

Coalbed methane (CBM) resources in No.15 coal seam of Taiyuan Formation account for 55% of the total CBM resources in southern Qinshui Basin (SQB), and have a great production potential. This study aims at investigating the CBM production in No.15 coal seam and its influence factors. Based on a series of laboratory experiments and latest exploration and development data from local coal mines and CBM companies, the spatial characteristics of gas production of No.15 coal seam were analyzed and then the influences of seven factors on the gas productivity of this coal seam were discussed, including coal thickness, burial depth, gas content, ratio of critical desorption pressure to original coal reservoir pressure (RCPOP), porosity, permeability, and hydrogeological condition. The influences of hydrological condition on CBM production were analyzed based on the discussions of four aspects: hydrogeochemistry, roof lithology and its distribution, hydrodynamic field of groundwater, and recharge rate of groundwater. Finally, a three-level analytic hierarchy process (AHP) evaluation model was proposed for predicting the CBM potentials of the No.15 coal seam in the SQB. The best prospective target area for CBM production of the No.15 coal seam is predicted to be in the districts of Panzhuang, Chengzhuang and south of Hudi.     

Comparative analysis of significant wave height between a new Southern Ocean buoy and satellite altimeter

中国于2019年第35次南极考察中,首次在南大洋布放了锚系实时综合观测浮标(西风带海洋环境监测浮标,WEMB),为深入了解此海区的海洋环境变化提供了宝贵资料.国家海洋技术中心WEMB研究团队基于AVISO公开发布的多颗卫星高度计L3产品,通过数据配对,误差统计和最小二乘线性拟合等方法,对西风带海洋环境监测浮标的有效波高数据误差进行了分析与校正.校正后的浮标有效波高统计显示西风带常年处于大浪以上海况,观测期间内57％处于巨浪海况,并且伴随有高度相关的大风天气.     

藏南冈底斯岩基东段朗县杂岩早白垩世岩浆作用:新特提斯洋二次俯冲

新特提斯洋长期俯冲消减作用在早白垩世可能经历二次俯冲启动或板片俯冲几何形态的重大转换。确定西藏南部冈底斯岩基早白垩世岩浆作用的岩石地球化学特征和作用方式是甄别上述过程的关键,对理解新特提斯洋的俯冲演化过程至关重要。本文就冈底斯岩基东段朗县杂岩中保存的各类早白垩世岩浆岩,开展了锆石U-Pb地质年代学和Hf同位素、全岩元素和同位素（Sr-Nd）组成分析。数据结果表明：1）基性岩侵位时代为早白垩世晚期（103.6~100.8Ma）,为高钾钙碱性偏铝质岩石,锆石ε_Hf（t）=+0.3~+5.7,全岩ε_Nd（t）=-0.8和-0.3,暗示其岩浆源区具有大量俯冲沉积物或流体的混入,为沉积物熔体和流体交代的地幔楔物质部分熔融的产物,经历了一定程度的角闪石分离结晶作用;2）中性岩形成于99.8~97.6Ma,略晚于基性岩,其主量元素与基性岩具有较好的线性关系,全岩ε_Nd（t）=+1.1,具有较多的地幔物质参与,为基性岩浆进一步演化形成;3）酸性岩（脉体）记录了多阶段岩浆作用（124.1~95.3Ma）,根据同位素组成不同进一步划分为两类,第一类具有较低的全岩ε_Nd（t）值（-8.3~-6.0）,其岩浆源区显示富集特征,t_DM2=1385~1586Ma,由古老地壳物质的再熔融形成;第二类的锆石ε_Hf（t）值（-2.8~+3.2）变化较大,岩脉的锆石ε_Hf（t）=+0.4~+8.1,t_DM=428~906Ma,全岩ε_Nd（t）=+0.1和+0.8,表明岩浆源区具有不均一性,为古老地壳物质被富流体地幔岩浆改造形成;和4）镁铁质包体的主量元素与寄主花岗岩具有较好的线性关系,锆石的Hf同位素组成变化较大（ε_Hf（t）=-9.3~+4.1）,变化范围可达13个ε单位,为岩浆混合成因。寄主花岗岩和角闪辉长岩分别作为酸性和基性端元,是基性岩浆与其诱发古老地壳熔融形成的花岗质岩浆经混合形成。结合冈底斯岩基早白垩世岩浆岩的研究结果,朗县杂岩在早白垩世（124~97Ma）的岩浆作用具有明显的岩浆混合现象,锆石Hf和全岩Sr-Nd同位素组成变化较大,可达13个ε单位,其岩浆源区复杂且富含流体,代表了新特提斯洋在早期（240~144Ma）经历漫长的俯冲之后,在早白垩世时期（~120Ma）俯冲带发生跃迁或俯冲角度达到临界点,导致大量俯冲沉积物和流体沿俯冲带俯冲下去,与发生部分熔融的地幔楔物质混合,底侵导致上覆古老地壳物质的再熔融,形成早白垩世复杂的岩浆岩组合,很可能是新特提斯洋二次俯冲开始的标志。     

Geochronological and geochemical evidence for a Late Ordovician to Silurian arc-back-arc system in the northern Great Xing'an Range,NE China

The early Paleozoic tectonic evolution of the Xing'an-Mongolian Orogenic Belt is dominated by two oceanic basins on the northwestern and southeastern sides of the Xing'an Block,i.e.,the Xinlin-Xiguitu Ocean and the Nenjiang Ocean.However,the early development of the Nenjiang Ocean remains unclear.Here,we present zircon U-Pb geochronology and whole-rock elemental and Sr-Nd isotopic data on the gabbros in the Xinglong area together with andesitic tuffs and basalts in the Duobaoshan area.LA-ICP-MS zircon U-Pb dating of gabbros and andesitic tuffs yielded crystallization ages of 443-436 Ma and 452-451 Ma,respectively.The Early Silurian Xinglong gabbros show calc-alkaline and E-MORB affinities but they are enriched in LILEs,and depleted in HFSEs,with relatively low U/Th ratios of 0.18-0.36 andεNd(t)values of-1.6 to+0.5.These geochemical features suggest that the gabbros might originate from a mantle wedge modified by pelagic sediment-derived melts,consistent with a back-arc basin setting.By contrast,the andesitic tuffs are characterized by high MgO(>5 wt.%),Cr(138-200 ppm),and Ni(65-110 ppm)contents,and can be termed as high-Mg andesites.Their low Sr/Y ratios of 15.98-17.15 and U/Th values of 0.24-0.25 and moderate(La/Sm)_n values of 3.07-3.26 are similar to those from the Setouchi Volcanic Belt(SW Japan),and are thought to be derived from partial melting of subducted sediments,and subsequent melt-mantle interaction.The Duobaoshan basalts have high Nb(8.44-10.30 ppm)and TiO2 contents(1.17-1.60 wt.%),typical of Nb-enriched basalts.They are slightly younger than regional adakitic rocks and have positiveεNd(t)values of+5.2 to+5.7 and are interpreted to be generated by partial melting of a depleted mantle source metasomatized by earlier adakitic melts.Synthesized with coeval arc-related igneous rocks from the southeastern Xing'an Block,we propose that the Duobaoshan high-Mg andesitic tuffs and Nbenriched basalts are parts of the Late Ordovician and Silurian Sonid Zuoqi-Duobaoshan arc belt,and they were formed by the northwestern subduction of the Nenjiang Ocean.Such a subduction beneath the integrated Xing'an-Erguna Block also gave rise to the East Ujimqin-Xinglong igneous belt in a continental back-arc basin setting.Our new data support an early Paleozoic arc-back-arc model in the northern Great Xing'an Range.     

1961—2010年中国气候生产潜力时空格局变化及其潜在可承载人口分析

以气温、降水格点数据为基础,采用Thornthwaite Memorial模型计算了中国气候生产潜力(CPP),并从气候的角度估算了耕地上气候资源潜在可承载的人口数,以便增强了解气候变化的影响及气候资源最大人口支撑能力。结果表明:1961—2010年中国CPP总体呈突变性增加趋势,1987年为突变点,年最低、最高及平均值分别为689. 18、814. 56和744. 05 g·m^-2·a^-1。空间上呈现出从西北向东南逐渐递增的带状分布,其中高值区主要分布在华南大部,最高值达2103. 56 g·m^-2·a^-1;低值区主要分布在西、北部地区,最低值为39. 28 g·m^-2·a^-1。2001—2010年中国大部分地区CPP年平均值相对于1961—2010年多年平均值变化幅度不大,变化比例高的地区基本上分布于中国西、北部,其中增加的区域达82%,主要分布在华东地区、新疆西部、西藏北部及青海大部,远大于缩减的区域(17%)。1995—2010年,基于公里网格的耕地气候潜在可承载人口为46—2180人·km^-2,全国平均值最低的年份为1130人·km^-2,对应的实际人口为0—49729人·km^-2,全国平均值均不高于137人·km^-2;全国实际总人口为11. 43—13. 04亿,耕地气候潜在可承载总人口为19. 72—20. 22亿,前后比值为58%—65%。这表明,中国耕地生产力未达到气候生产潜力,尚有一定的开发潜力;实际人口在中国大部分地区均没有超出气候资源潜在可承载的最大人口,然而在少数省市(如生态环境脆弱的青海省以及经济发达的大城市及沿海地区)已超出。     

动机、成本、风险：家长视角下研学旅游产品价值感知研究

以中小学生自然教育研学旅游作为具体情境,基于539份家长问卷数据阐释研学旅游动机与价值感知之间的关系,并通过成本感知和风险感知探讨其内在机制和边界条件。结果表明,家长感知的研学旅游动机越强烈,越容易感知到研学旅游产品所传递的价值,验证了研学旅游情境下动机对价值感知的积极影响,也形成了对动机与价值之间关系研究的理论补充。并且,这一动机除了直接作用于价值感知外,还会通过成本感知的部分中介作用影响价值感知,揭示了中国家长对于教育价值的重视会削弱其对“利失”的感知。此外,进一步验证了风险感知的积极影响,即家长感知研学旅游的不确定性水平越高,动机对价值感知的积极影响越明显,且会抑制成本感知对价值感知的负向作用,但风险感知水平达到一定高度时,其对成本感知与价值感知间的抑制作用将不显著。因此,面向需求设计打造产品,突出产品价值、加大宣传营销力度、把控活动安全、合理制定价格,获取家长群体的认同接受,将是研学旅游进一步拓展市场的重要考量。     

论直流激发极化法的视电阻率参数

直流激发极化法,计算视电阻率的一次场采集于供电方波的末端时间,从而包含了被激发形成的二次场。在高极化率地质体上,得到的视电阻率将削弱其低阻特性或放大高阻特性。为此,建议在野外工作中,应对所采集的一次场作适当的处理后,再计算视电阻率,以降低这种影响。     

兴安地块南段晚泥盆世包格德岩体时代的厘定及地质意义

中亚造山带东端兴安地块南段的包格德岩体由石英二长岩、二长花岗岩和花岗斑岩3种岩性组成,岩体锆石LA-ICP-MS U-Pb定年结果分别为368±+1 Ma、364±1 Ma、355±1 Ma,为晚泥盆-早石炭世岩浆活动的产物;岩体的(Na2O+K2O)含量为7.62％～8.82％,K2O/Na2O值为0.93～4.21...