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991.
第四系是与人类生活关系密切的地层,山区地带的第四系主要由河流沉积物组成,这些沉积物的表面风化程度具有重要的环境意义。四川省雅安市地区发育了中更新统砾石层构成的古冲积扇名邛冲积扇和丹思冲积扇,现今废弃于岷江与青衣江之间,遭受了不同程度的侵蚀风化。对两个冲积扇不同位置采集样品,尝试利用主量元素分析冲积扇的风化程度。经过实验发现,主量元素分析可以很好地应用于第四系的测试,砾石间填充的基质砂能够合理反映沉积物经历的风化过程。实验结果表明,沉积物主量元素中长石矿物元素Ca、Na大量流失,而稳定矿物元素Si、Ti等偏高,说明冲积扇经历了长期的风化淋溶作用。A-CN-K图解体现出冲积扇经历了早期的斜长石风化,已经进入以钾长石和伊利石风化为标志的中期阶段。Pettijohn图解表明名邛冲积扇样品含有更多的石英砂岩,沉积物的成熟度较高。这些指标说明名邛冲积扇相比丹思冲积扇经历了更强的风化作用。结合冲积扇的年龄发现,风化速度随年龄的增长呈现减速的特征,体现了风化作用的阶段性. 相似文献
992.
川西北早志留世陆源碎屑──碳酸盐混积缓坡 总被引:10,自引:6,他引:10
研究区位于扬子地块西北缘,由一套巨厚的页岩、泥岩层夹生物礁及透镜状和不规则层状风暴生屑灰岩、瘤状灰岩组成。根据区内特征的岩石类型及其组合、分布和相应的化石生态,作者认为本区兰多维列期至早温洛克期时为一典型的陆源碎屑--碳酸盐混积均斜缓坡,并且从浅到深划分为滨岸、浅缓坡、深缓坡及盆地等亚环境。滨岸区位于潮间带,以潮坪碳酸盐岩为代表;浅缓坡位于浪基面至风暴浪基面之间,岩性组合为A、B类风暴岩,A、B类瘤状灰岩、生物礁灰岩及粘结岩;深缓坡位于风暴浪基面至最大风暴浪基面之间,岩性以D、E类风暴岩、C类瘤状灰岩及泥页岩组合为特征;盆地处于最大风暴浪基面之下,为黑色泥页岩沉积。结合早志留世时全球冰川作用,文中讨论了海平面变化的原因及对环境的影响。 相似文献
993.
贵州绥阳双河洞系的发育与成因探讨 总被引:4,自引:6,他引:4
绥阳双河洞是发育在早古生代白云岩体内的多层多支,并彼此有水力联系的复杂洞群,根据贵州洞穴协会实测,洞长达35.2km。文章在实地考察的基础上,分析主要洞道的分布与特征,研究了洞穴发育与硫酸盐岩及含SO地下水的密切关系,并探讨了石膏源及洞穴发育演化的过程。 相似文献
994.
Jianpo Guo Fenghui Zhang Xianfei Zhang Zhanwen Han 《Astrophysics and Space Science》2010,325(1):25-30
Ultraviolet radiation is a double-edged sword to life. If it is too strong, the terrestrial biological systems will be damaged.
And if it is too weak, the synthesis of many biochemical compounds cannot go along. We try to obtain the continuous ultraviolet
habitable zones, and compare the ultraviolet habitable zones with the habitable zones of host stars. Using the boundary ultraviolet
radiation of ultraviolet habitable zone, we calculate the ultraviolet habitable zones of host stars with masses from 0.08
to 4.00 M
⊙. For the host stars with effective temperatures lower than 4,600 K, the ultraviolet habitable zones are closer than the habitable
zones. For the host stars with effective temperatures higher than 7,137 K, the ultraviolet habitable zones are farther than
the habitable zones. For a hot subdwarf as a host star, the distance of the ultraviolet habitable zone is about ten times
more than that of the habitable zone, which is not suitable for the existence of life. 相似文献
995.
996.
在分析以往煤炭资源管理信息系统优缺点的基础上,利用Visual C++6.0、SQL Server2000、ADO技术以及MapGIS二次开发技术,开发了山西省煤炭资源有效保障能力分析信息系统。该系统具有数据管理、信息查询、地图操作、统计输出、环境承载力评价、煤炭用途评价、煤炭优质环保评价、矿井资源保障度评价、估算井田生产规模等功能,为煤炭资源管理提供适时、动态和高效有序的资源数据,为加强煤炭资源的开发部署及管理,制定能源政策以及中长期规划,合理开发利用煤炭资源,保障煤炭工业可持续发展提供科学的宏观决策依据。 相似文献
997.
The effects of human activities on climate change are a significant area of research in the field of global environmental change. Land use and land cover change(LUCC) has a greater effect on climate than greenhouse gases, and the effect of farmland expansion on regional drought is particularly important. From the 1910 s to the 2010 s, cultivated land in Songnen Plain increased by 2.67 times, the area of cultivated land increased from 4.92×10~4 km~2 to 13.14×10~4 km~2, and its percentage of all land increased from 25% to 70%. This provides an opportunity to study the effects of the conversion of natural grassland to farmland on climate. In this study, the drought indices in Songnen Plain were evaluated from the 1910 s to the 2010 s, and the effect of farmland expansion on drought was investigated using statistical methods and the Weather Research and Forecasting Model based on UK's Climatic Research Unit data. The resulting dryness index, Palmer drought severity index, and standardized precipitation index values indicated a significant drying trend in the study area from 1981 to 2010. This trend can be attributed to increases in maximum temperature and diurnal temperature range, which increased the degree of drought. Based on statistical analysis and simulation, the maximum temperature, diurnal temperature range, and sensible heat flux increased during the growing season in Songnen Plain over the past 100 years, while the minimum temperature and latent heat flux decreased. The findings indicate that farmland expansion caused a drying trend in Songnen Plain during the study period. 相似文献
998.
Xiumei Zhang Shen Zhang Weimin Ying Tianshan Ren Cuihua Xu Zhizhao Zhong Shurong Zhang 《GeoJournal》1996,40(1-2):201-208
In this paper210 Pb and 137Cs dating methods were used to determine sedimentation rates of lakes Dianchi, Erhai and Poyanghu, and to establish the time scale of the sediments. Also based on geochemical records in the sediment column, the historical variation in heavy metal content over the past one hundred years was determined. Some element concentration increased rapidly after the 1970s, such as Cu, Zn and Mn in the sediments of northern Lake Dianchi, Cd and Mn in southern Lake Erhai and in the west central parts of Lake Poyanghu, Our investigations indicate that the increase in element concentration is caused by human activities. In order to understand the extent of the effect caused by human activities, we have calculated the flux of Zn, Cd and Mn. Results show that the flux caused by human activities is seven times greater than the natural one and the ratio is about 2 times in Lake Erhai and Lake Poyanghu. 相似文献
999.
The Suzhou granite suite is the anorogenic product, which is located on the inactive continental margin of east China. It
was emplaced about 141 Ma ago, occurring as a stock with a polygonal outline on the surface, belonging to alkali potash-feldspar
granites with K2O > Na2O, Reit’s alkali coefficient = 0.694, SiO2 = 74.95, and Al2O3/(K2O + Na2O)mol= 1. Besides K and Na, Li and Rb are also rather high. Highlycharged metals such as Zr, Nb, REE, Y, Sn, Th, Ga and Zn are 10,
or even 50 times higher than those in the ordinary granites. Halogen elements such as F and Cl are high in abundance with
F = 2700 ppm and Cl = 170 ppm on average. The abundances of deep-source elements such as Ti, Al, Ca, Mg and P are relatively
low, with A12O3 = 12.65% and Ca + Mg < 1%. High Ga and low Al contents are typomorphically characteristic of A type granites.
Biotite in the rocks is, for the most part, annite, usually filling in quartz and feldspar crystals, indicating that the crystallization
of magma proceeded under relatively anhydrous condition.
More than 40 kinds of accessory minerals have been identified, of which the mantle-derived mineral chrompicotite and moissanite
is of great interest.
Two different intrusions, the major and supplementary intrusions, can be distinguished in the granite suite. The rock-forming
temperature is estimated to be 810°C, pressure 2.5 kbars, pH 8.1,18O/16O low(δ18OWR = 6.19‰), andfo2= 10−16. The abundances of REE are high and Eu depletion is remarkable (δEu = 0.24).
A variety of mineral deposits related to the Suzhou granite suite have been recognized. 相似文献
1000.