华北克拉通西南缘高山河组凝灰岩锆石U- Pb年龄及其地质意义

华北克拉通西南缘高山河组是中元古代重要的地层单元之一,但其沉积时限和地层对比关系长期存在争论。本文对采自甘肃省华亭县马峡镇高山河组下部的凝灰岩进行了LA-ICP-MS锆石U-Pb同位素年龄测定,获得凝灰岩样品的高精度年龄为1759±17Ma。结合区域资料和前人研究成果,初步将该地区高山河组的形成年代限定在1770～1600Ma之间,并进一步限定高山河组下部熊耳群火山岩系的形成时代介于1800～1770Ma之间。此为首次在华北克拉通西南缘高山河组获得高精度年龄,不仅确定了高山河组沉积时代应为长城纪,也为整个华北克拉通西南缘中元古代地层划分对比和地质演化及其进一步进行微古生物研究等地质问题奠定了重要的年代学基础。     

内蒙古赵井沟钾长花岗岩锆石U-Pb定年、Hf同位素和岩石地球化学特征

赵井沟铌钽矿与区内花岗岩关系非常密切,锆石LA-ICP-MS U-Pb定年结果表明矿区内黑云母钾长花岗岩形成时代为125±1 Ma。岩石地球化学分析结果显示,矿区内晚中生代岩浆岩为准铝质-弱过铝质碱性岩类,属于高钾钙碱性系列,具有轻稀土元素富集、Eu强负异常、大离子亲石元素(Rb、Th、U)和高场强元素(Hf、Y)强烈富集的地球化学特征,属于A1亚类的A型花岗岩;锆石~(176)Hf/~(177)Hf值介于0. 000 5～0. 003 0之间,ε_(Hf)(t)值为-15. 42～-5. 55,对应的模式年龄t_(DM2)变化于2 247～1 640 Ma之间。花岗岩浆主要来源于地壳物质部分熔融的产物。     

460矿床关键控矿要素重磁异常特征及深部结构研究

通过在460矿床开展重、磁勘探工作,研究了控矿要素的重、磁异常特征,分析了主要断裂构造、火山机构、主要岩体的分布情况;利用重磁联合二维正反演、密度界面反演推断了研究区基底界面深度;利用地表地质条件作为约束三维密度反演推断了研究区3大地层的空间分布。研究表明,重磁勘探在火山岩地区确定盆地范围、识别断裂构造效果明显,矿床位置一般位于重磁高场向低场的过渡区域,重磁梯度带是寻找铀矿的重要标志。     

Evaluation of CO2 solubility-trapping and mineral-trapping in microbial-mediated CO2–brine–sandstone interaction

Evaluation of CO₂ solubility-trapping and mineral-trapping by microbial-mediated process was investigated by lab experiments in this study. The results verified that microbes could adapt and keep relatively high activity under extreme subsurface environment (pH < 5, temperature > 50 °C, salinity > 1.0 mol/L). When microbes mediated in the CO₂–brine–sandstone interaction, the CO₂ solubility-trapping was enhanced. The more biomass of microbe added, the more amount of CO₂ dissolved and trapped into the water. Consequently, the corrosion of feldspars and clay minerals such as chlorite was improved in relative short-term CO₂–brine–sandstone interaction, providing a favorable condition for CO₂ mineral-trapping. Through SEM images and EDS analyses, secondary minerals such as transition-state calcite and crystal siderite were observed, further indicating that the microbes played a positive role in CO₂ mineral trapping. As such, bioaugmentation of indigenous microbes would be a promising technology to enhance the CO₂ capture and storage in such deep saline aquifer like Erdos, China.     

Seasonal variability of zonal heat advection in the mixed layer of the tropical Pacific

Zonal heat advection （ZHA） plays an important role in the variability of the thermal structure in the tropical Pacific Ocean, especially in the western Pacific warm pool （WPWP）. Using the Simple Ocean Data Assimilation （SODA） Version 2.02/4 for the period 1958-2007, this paper presents a detailed analysis of the climatological and seasonal ZHA in the tropical Pacific Ocean. Climatologically, ZHA shows a zonal- band spatial pattern associated with equatorial currents and contributes to forming the irregular eastern boundary of the WPWP （EBWP）. Seasonal variation of ZHA with a positive peak from February to July is most prominent in the Nifio3.4 region, where the EBWP is located. The physical mechanism of the seasonal cycle in this region is examined. The mean advection of anomalous temperature, anomalous advection of mean temperature and eddy advection account for 31%, 51%, and 18% of the total seasonal variations, respectively. This suggests that seasonal changes of the South Equatorial Current induced by variability of the trade winds are the dominant contributor to the anomalous advection of mean temperature and hence, the seasonality of ZHA. Heat budget analysis shows that ZHA and surface heat flux make comparable contributions to the seasonal heat variation in the Nifio3.4 region, and that ZHA cools the upper ocean throughout the calendar year except in late boreal spring. The connection between ZHA and EBWP is further explored and a statistical relationship between EBWP, ZHA and surface heat flux is established based on least squares fitting.     

沙漠腹地人工绿地地表能量交换特征

运用涡度相关法开路系统对塔克拉玛干沙漠腹地人工灌溉绿地生长季地表能量交换特征以及与环境因子的关系进行测定分析。结果表明：在典型晴天条件下,无论是沙漠区还是沙漠腹地灌溉绿地,白天感热通量在净辐射通量的分配中所占的份额最大,潜热交换仅占很小的比例,人工绿地感热通量和潜热通量的峰值为230.54 W/m²和88.5 W/m²,沙漠区为220 W/m²和17.55 W/m²,沙漠腹地人工灌溉造林后潜热交换明显增加。沙漠腹地造林后,绿地波文比日变幅和日均波文比均减小,绿地日均波文比为沙漠区的15%,人工绿地的营建促使了局地气候的改变。绿地地表能量交换受气象因子和下垫面条件的影响和制约,按相关系数的高低,环境因子对感热、潜热通量的影响依次为：Rn>△Ta>△TS>v>TS,沙漠区人工造林后地表能量交换与多个环境因子有着密切的关系。这些研究结果将加深我们对沙漠地区人工灌溉造林地近地层能量交换的认识。     

Numerical tests for effects of various parameters in niching genetic algorithm applied to regional waveform inversion

In this paper, we focus on the influences of various parameters in the niching genetic algorithm inversion procedure on the results, such as various objective functions, the number of the models in each subpopulation, and the critical separation radius. The frequency–waveform integration (F–K) method is applied to synthesize three-component waveform data with noise in various epicentral distances and azimuths. Our results show that if we use a zero-th-lag cross-correlation function, then we will obtain the model with a faster convergence and a higher precision than other objective functions. The number of models in each subpopulation has a great influence on the rate of convergence and computation time, suggesting that it should be obtained through tests in practical problems. The critical separation radius should be determined carefully because it directly affects the multi-extreme values in the inversion. We also compare the inverted results from full-band waveform data and surface-wave frequency-band (0.02–0.1 Hz) data, and find that the latter is relatively poorer but still has a higher precision, suggesting that surface-wave frequency-band data can also be used to invert for the crustal structure.     

Stable carbon and hydrogen isotopes of gases from the large tight gas fields in China

By the end of the year 2010,a total of 15 large tight gas fields have been found in China,located in the Ordos,Sichuan,and Tarim basins.The annual production and total reserves of these fields in 2010 were 222.5×108and 28657×108m3,respectively,accounting for 23.5%and 37.3%,respectively,of the total annual production and reserves of natural gases in China.They took a major part of all natural gas production and reserves in China.According to the analyses of 81 gas samples,the stable carbon and hydrogen isotopic compositions of tight gases in China have following characteristics:(1)Plots of 13C1-13C2-13C3,13C1-C1/C2+3and 13C1-13C2demonstrate the coal-derived origin of tight gases in China;(2)For the primary alkane gases,both carbon and hydrogen isotopic values increase with increasing molecular mass,i.e.,13C113C213C313C4and2H12H22H3;(3)The isotopic differences of 13C2-13C1,13C3-13C1,2H2-2H1and 2H3-2H1decrease with increasing Ro(%)and C1/C1–4;(4)There are seven causes for the carbon and hydrogen isotopic reversal,however,the carbon and hydrogen isotopic reversal of tight gases in China is caused mainly by multiple stages of gas charge and accumulation.     

Origin area and migration route: Chloroplast DNA diversity in the arctic-alpine plant Koenigia islandica

The Hengduan Mountains (henceforth H-D Mountains) on the Tibet Plateau are a distribution and diversity center for many alpine genera. We examine patterns of genetic variation in an arctic-alpine plant to evaluate the possibility that the H-D Mountains constitute the area of origin of the species as well as to uncover postglacial migration routes. 220 individuals of the arctic-alpine plant Koenigia islandica were sampled from 26 populations distributed in western China and northern Finland. DNA haplotypes were identified using restriction site analysis of two chloroplast DNA intergene spacer regions, atpB-rbcL and trnL-trnF. We examined the geographical distribution of haplotype diversity in relation to latitude, and also compared various indices of diversity in putatively glaciated and unglaciated regions. Patterns of migration were inferred using nested clade analysis. A total of 25 haplotypes were detected. High haplotype diversity was found in the H-D Mountains. H3 and its radiated haplotypes were distributed in the Himalayas. Two haplotypes were fixed concurrently in the H-D Mountains and northern Finland. High genetic diversity of K. islandica and high species diversity of K. islandica are expected in the origin area. Our observations suggest that the H-D Mountains are not only the place of origin of K. islandica, but also the refugia for K. islandica on the Tibet Plateau. What is more, the migration route for the arctic-alpine plant K. islandica must have originated in the region defined by the H-D Mountains in western China extending northward to the Arctic circumpolar, and moved westward along the Himalayas, then northward across the Altay Mountains and the Central Siberian Plateau at different time periods.