洞穴石笋沉积特征研究--以贵州荔波董歌洞4号石笋为例

在综合研究南方20多个大型石笋纵剖面的基础上,以董歌洞4号石笋为代表,论述石笋沉积特征与气候演化的对应性.4号石笋从距今147.838±2.6 ka开始沉积以来,形成了53个沉积纹(壳)层组,组成24个亚旋回,构成9个旋回,呈现韵律式旋回性沉积特征.石笋纹(壳)层组分、结构、叠复构造呈多级次旋回性很突出,其中沉积间断具普遍性、沉积速率具多变性,间断和速率变化级次亦明显.以系统测试和测年引证沉积特征的同时揭示:①～⑨旋回间沉积间断时间累积达75.804 ka,占石笋形成时间的51.21%,①～⑨旋回实际沉积时间仅72.222 ka,占形成时间的48.79%;④旋回之前,沉积速率很小,最小仅0.36 mm/100a,比最大速率小22～24倍,自⑤旋回起,沉积速率很大,最大达39.03 mm/100a,是最小速率的3.8倍.石笋沉积特征与气候环境演化的成生关系表明,石笋沉积多旋回性的纹(壳)层组、亚旋回、旋回与气候演化的气候期、阶段和旋回彼此对应,石笋沉积的多级次旋回及其变化就是气候演化的级次及旋回性转(跃)变时间,彼此同时显示.论证了石笋沉积的多旋回性与气候演化的不稳定性,及其彼此协调的宏观、微观综合表现特征.     

贵州荔波1200年来石笋高分辨率的古气候环境记录

通过笔者对荔波龙泉洞L2石笋进行高精度的ICP-MS-230Th测年和碳、氧同位素分析, 建立了荔波地区1200 a BP 来高分辨率的古气候变化的时间序列。研究结果表明, 荔波地区1200 a BP以来石笋记录的季风气候经历了1200~1100 a BP(暖)、1100~940 a BP (冷)、940~840 a BP(暖)、840~700 a BP(冷)、700~450 a BP(暖)、450~300 a BP(冷)、300~200 a BP(暖)以及200~70 a BP(冷)等8个阶段百年尺度的干湿、冷暖波动, 并在这些百年尺度的波动上又叠加了一系列数十年尺度的气候变化。石笋记录揭示了1200 a以来东亚季风气候的不稳定性, 呈百年尺度(Gleissberg)的周期性变化。这些气候变化事件, 与冰芯记录极为相似, 反映低纬度地区百年尺度石笋记录的季风气候变化与高纬度及北极地区的气候变化具有极好的相关性, 反映百年尺度石笋记录的季风降水主要受太阳辐射驱动、控制, 而东亚季风的降水事件(或干旱事件)与太阳的辐射强度密切相关。石笋记录的百年尺度季风降水事件对于认识现代气候系统变化以及对未来十年—百年尺度的气候预测和演化的驱动机制, 具有重要的科学意义。     

松科二井东孔营城组火山岩测井响应特征及岩性评价

为开展松辽盆地深部长期观测、流体实验和探索白垩纪火山事件,利用松科二井东孔丰富、齐全的测井资料,对营城组火山岩岩性进行评价。通过测井响应特征分析发现,松科二井东孔营城组凝灰岩具有最强的放射性和导电性,高孔隙度的集块熔岩密度为低值,流纹岩表现出高密度和低导电性。利用测井交会图和成像识别模式,识别出松科二井东孔营城组火山岩以流纹岩、凝灰熔岩和集块熔岩为主,少量的凝灰岩。结合凝灰岩处测井曲线变化特点,证明了火山喷发间断的存在。流纹岩具有高碱、高Si、低Fe和低黏土矿物特征。T_2谱分析认为流纹岩有利于后期深部长期观测和流体实验的开展。研究成果对松科二井东孔后续火石岭组火成岩及整个松辽盆地火山岩研究具有一定的参考价值。     

Coastline and landscape changes in bay areas caused by human activities: A comparative analysis of Xiangshan Bay,China and Tampa Bay,USA

Using multitemporal Landsat TM/OLI images at a 10-year interval, in this study, we (1) extracted information of spatial location, length, and sinuosity of coastline and landscape configuration, diversity and fragmentation in the bay areas of Xiangshan Bay (XB), China and Tampa Bay (TB), USA from 1985 to 2015; (2) constructed indices of artificial coastlines and human disturbance on bay area landscapes; and (3) explored and discussed the impacts of human activities on changes of coastlines and landscape types in the two bay areas. Our analysis results demonstrate the following five points. (1) During the past 30 years, the lengths of natural coastline in XB and TB shrank, while the lengths of their artificial coastline increased first and then maintained stable. Since there were different influences of human activities on coastlines and landscape types between the two bay areas, XB experienced dramatic changes in parts of coastline geomorphologies and continuous decrease of coastline sinuosity, while, in TB, there was a little change in coastline geomorphologies and its coastline sinuosity was almost unchanged. (2) The intensity of human activities in XB was continuously enhanced from 1985 to 1995, and then the degree of enhancement had slowed down after 1995. However, in the time period, the impacted extent of human activities gradually increased and finally covered almost entire coastlines in XB. In TB area, although the intensity of human activities was enhanced, the degree of enhancement slowed down from 1985 to 2015 and the impacted areas of human activates were concentrated in several coastal city areas. (3) The average area of landscape patches strongly disturbed by human activities in both XB and TB generally showed a trend of decreasing from 1985 to 2005. However, during the period of 2005 to 2015, the average patch area of landscapes disturbed by different degrees of human activities in XB changed differently, while in TB it almost did not change. (4) From 1985 to 2005, the indices of landscape diversity in various areas of human disturbance in XB gradually increased, while in TB, changes in indices of the landscape diversity varied. From 2005 to 2015, the changes in the intensity of human disturbance in both bay areas were from weak to strong, whereas the indices of landscape diversity in XB and TB increased first and then decreased. (5) The landscape fragmentation index in different human disturbance areas in both XB and TB gradually increased from 1985 to 2005, while from 2005 to 2015, in both bay areas, the landscape fragmentation index presented a decreasing trend.     

腾格里沙漠生态系统不同固沙方式下昆虫群落的生态位分异研究

利用样方法研究了腾格里沙漠生态系统无脊椎动物的群落组成和以生活方式划分的功能群的特征,并计算了主要动物类群的生态位宽度及各类群间的生态位重叠.结果表明:不同的沙地固定方式下,动物群落的演替方向不同.油蒿(Artemisia ordosica)是优势动物类群的主要食物资源和生活场所,其他动物类群数尽管较多,但个体数量和生物量是相对较低的.从功能群的角度出发,蛀根性昆虫种类在整个动物群落中占有重要地位.在A区中蛀根性昆虫种类仅发现有吉丁甲科和象甲科昆虫幼虫,与B、C、D区比较,无蠹蛾科幼虫寄生,并且其根被蛀的程度和寄生率也较轻,夜蛾科幼虫在A区亦无分布.生态位重叠的计算结果并不显示在生活习性相同或相似的动物类群之间有较大的生态位重叠.     

土地利用/覆被变化的大气环境效应研究进展

土地利用/覆被变化是全球环境变化的重要原因,随着气候变化问题的日益突出,土地利用/覆被变化的大气环境效应已成为国内外全球变化的前沿和热点课题.通过对土地利用/覆被变化对大气环境系统的作用机制分析,认为目前土地利用/覆被变化对大气质量、大气污染以及气候变化产生了重要的影响,尤其随着快速城市化进程的推进,带来了显著的城市空气污染和热岛效应,而土地利用/覆被变化在全球尺度上的气候效应则存在较多的争论.今后应加强土地变化科学和大气科学的融合,从多尺度探讨土地利用/覆被变化的大气环境效应,并注重大气环境改善视角下的土地利用策略和空间规划研究.     

Re–Os dating of molybdenite and in-situ Pb isotopes of sulfides from the Lamo Zn–Cu deposit in the Dachang tin-polymetallic ore field,Guangxi, China

The Dachang tin-polymetallic district, Guangxi, China, is one of the largest tin ore fields in the world. Both cassiterite-sulfide and Zn–Cu skarn mineralization are hosted in the Mid-Upper Devonian carbonate-rich sediments adjacent to the underlying Cretaceous Longxianggai granite (91–97 Ma). The Lamo Zn–Cu deposit is a typical skarn deposit in the district and occurs at the contact zone between the Upper Devonian limestone and the granite. The ore minerals mainly consist of sphalerite, arsenopyrite, pyrrhotite, galena, chalcopyrite, and minor molybdenite. However, the age of mineralization and source of the metals are not well constrained. In this study, we use the molybdenite Re–Os dating method and in-situ Pb isotopes of sulfides from the Lamo deposit for the first time in order to directly determine the age of mineralization and the tracing source of metals. Six molybdenite samples yielded a more accurate Re–Os isochron age of 90.0 ± 1.1 Ma (MSWD = 0.72), which is much younger than the reported garnet Sm–Nd isochron age of 95 ± 11 Ma and quartz fluid inclusions Rb–Sr isochron age of 99 ± 6 Ma. This age is also interpreted as the age of Zn–Cu skarn mineralization in the Dachang district. Further, in this study we found that in-situ Pb isotopes of sulfides from the Lamo deposit and feldspars in the district’s biotite granite and granitic porphyry dikes have a narrow range and an overlap of Pb isotopic compositions (²⁰⁶Pb/²⁰⁴Pb = 18.417–18.594, ²⁰⁷Pb/²⁰⁴Pb = 15.641–15.746, and ²⁰⁸Pb/²⁰⁴Pb = 38.791–39.073), suggesting that the metals were mainly sourced from Cretaceous granitic magma.     

微量元素在幔源矿物与热液之间分配系数的研究进展

微量元素在幔源矿物与热液之间分配系数的差异是造成地幔不均一的一个重要因素，对于认识地球演化、元素的分异和板块构造具有重要的意义。热液的组成、矿物的结构、温度、压力以及氧逸度都与分配系数密切相关。不同微量元素在相同矿物或热液中的分配系数存在差别，而相同的元素在不同矿物中的分配系数也可能出现很大的变化，这是研究微量元素分异和不同地幔端员形成的理论基础。在较低的温度和压力下，热液的组成对分配系数的影响很大，随着温度和压力的升高，热液组成的影响逐渐减弱，而矿物的组成与结构的影响逐渐增大。由于分配系数影响因素的复杂性，因此在考虑地球深部微量元素的迁移和分异时需慎重对待。     

湖北秭归地区震旦系灯影组白云岩地球化学特征及其成因意义

白云岩化流体性质与成岩作用是近年来碳酸盐岩成岩作用研究的热点,研究白云岩的成因有利于进一步认识白云岩储层的形成机制并为优质储层的预测提供依据。通过岩石学、矿物学(X射线衍射)、地球化学(微量元素、稀土元素、碳氧同位素)方法,系统研究湖北秭归地区灯影组不同类型白云岩的成因,并分析了可能的白云岩化模式。样品的微量元素特征显示,秭归地区白云岩未受到陆源碎屑物质的影响,形成于气候干旱、海水咸度较大且氧化的沉积环境中;Sr含量特征显示白云岩发生了较为彻底的白云岩化,其成岩环境为温度较高的埋藏环境,成岩过程中未受到淋滤作用的影响;秭归地区白云岩化流体主要来源于海水。结合蒸发白云岩(萨布哈)及埋藏白云岩化模式解释了秭归地区泥微晶白云岩及晶粒白云岩的形成过程。     

黔西北地区铅锌矿床流体包裹体与硫同位素地球化学研究

黔西北铅锌成矿区位于扬子地块西南缘,矿床产于不同时代的碳酸盐岩建造中,其矿物组合和热液蚀变特征类似于MVT型铅锌矿床。本文通过对该区部分铅锌矿床的矿石显微岩相学结构、矿物学与地球化学、脉石矿物和闪锌矿中流体包裹体岩相学与显微测温学以及硫同位素地球化学等研究,确定了该类型矿床成矿流体的性质及其成矿过程。结果表明,黔西北地区不同赋矿层位铅锌矿床具有相似的成矿流体特征,为中低温(160~260℃)、较高盐度(10%~22%NaCleqv)、含有低密度的CO_2、CH_4和N_2的卤水,不同于MVT型铅锌矿床成矿流体特征;硫同位素地球化学研究揭示,这些铅锌矿床硫化物的δ~(34)S范围均落在对应赋矿地层时代蒸发岩中的硫酸盐和生物成因硫化物的δ~(34)S演化曲线上或其附近,表明这些铅锌矿床硫化物中的S可能主要来源于对应地层本身。结合地球化学热力学分析,认为Pb、Zn等成矿元素的Cl络合物是成矿元素的主要搬运形式,富含Pb、Zn的成矿流体与赋矿地层中富含H_2S还原性流体的混合是铅锌富集成矿的重要机制之一。