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281.
282.
The incidence of lung cancer in the Gejiu area of Yunnan Province ranks the first in the world.The radon level(indoor,soil) was measured in the Gejiu area by the SSNTD method from 1990 to 1996,The result indicates an extensive high-level of indoor radon in that area though U and Th are lower in local limestones,The indoor radon level of houses located in the geologic fault zone is 6 times high that 2km far from the fault zone.The reason probably is that the radon level of soil in the fault is 6-8 times high that 1 km far from the faults.our data indicate that a lower range of radon levels,0-100Bq.m^-3,exists in healthy families.However,a higher radon level,over 800 Bq.m^-3,is often found corresponding to that of cancer patients‘ homes(the house-owners are suffering from either lung cancer or leukaemia or liver cancer),Obviously,an increase in lung cancer incidence follows an increase in indoor radon level,The risk of cancer induced by indoor radon is no longer an inference,but a fact. 相似文献
283.
Stanley W. Trimble 《Environmental Geology》1997,32(3):230-234
A significant proportion of stream sediment yield in North America comes from stream channel and bank erosion. One method
used for stream stabilization is the bank installation of timber and stone fish-shelter structures, but there is little evidence
for their potential effectiveness. Nine to nineteen years of precise survey data from Coon Creek, Wisconsin, however, show
that fish structures enhance sediment deposition along the stream and may retard lateral migration of channels. Such structures
have greater utility for sediment control when streams are eroding away a high bank and replacing it with a lower bank.
Received: 18 October 1996 · Accepted: 4 February 1997 相似文献
284.
金矿化作用伴围岩蚀变,且多受断裂控制,反映在地球化学上出现某些元素的异常。在已发现一害矿化体并掌握一般控制矿特征的地区,利用已有工程在蚀变带内连续捡块采样,分析有关批示元素,总结有关的地球化学指标,建立地球化学预测模式,对已知矿体及外围异常进行了地球化学评价。 相似文献
285.
小山水电站导流洞出口边坡其地质结构为下部中侏罗世安山岩(αJ2),其上覆盖了第三纪末第四纪初的玄武岩(βN~Q),两者间为不整合接触,不整合面夹有0.1~0.6m厚的粘土状及碎石粘土状夹层,产状倾向河床,倾角±25°。在上覆玄武岩层中见有高倾角的宽张裂隙带,与不整合面一起构成松动岩体,不整合面为底滑面。通过边界条件的分析和稳定计算,松动岩体的抗滑系数K=3.102,边坡是稳定的。在施工过程中采取了相应的安全保护措施,导流洞出口提前28m进洞,节约挖方量60000m3,提前了工期。经三年多的施工到运行,边坡无异常变化,表明该项优化设计是可行的。 相似文献
286.
导水裂隙带高度预测途径探讨 总被引:3,自引:0,他引:3
导水裂隙带高度是设计防水煤(岩)柱尺寸的主要技术参数,是煤矿防治水工作的重要内容。详细论述了其研究现状及发展趋势,并提出了履岩体地质环境,履岩体力学环境和数值模拟技术三位一体的综合预测评价方法。 相似文献
287.
The Mount Raymond transverse zone (MRTZ) forms the east-west-trending boundary between the Wyoming salient of the Sevier fold-thrust belt and the Uinta/Cottonwood arch in north-central Utah. Major faults in the zone dip 40° to 45° north. Our structural analysis indicates that the MRTZ contains both contractional and extensional structures. The contractional structures (thrusts and related folds) initially formed as part of a southeast-verging, northeast-trending thrust system. This system gradually curved and merged to the north with the east-verging Absaroka thrust system in the apex of the Wyoming salient. The contrast in trend between structures in the MRTZ and those in the apex of the Wyoming salient reflects the initial curvature of the salient. This curve formed because the stratigraphic sequence involved in thrusting thinned gradually southward, toward the axis of a proto-Uinta arch. The present east-west trend of the MRTZ developed during Laramide uplift of the Unita/Cottonwood arch, an event which tilted the faults into their present position. Cenozoic crustal extension subsequently reactivated segments of the MRTZ. In sum, the evolution of the MRTZ illustrates how post-thrusting processes can affect the map-view geometry of thrust belts to create transverse zones. 相似文献
288.
Song-Yan Song Xue-Song Zhou Chun-Yong Wang Xian-Kang Zhang Jian-Li Song Yi Gong 《地震学报(英文版)》1997,10(1):15-25
On the basis of S wave information from Tai’an-Xinzhou DSS profile and with reference to the results from P-wave interpretation,
the 2-D structures, including S-wave velocity V
s, ratio γ between V
p and V
s; and Poisson’ s ratio σ, are calculated; the structural configuration of the profile is presented and the relevant inferences are drawn from the
above results. Upwarping mantle districts (V
s≈4.30 km/s) and sloping mantle districts (V
s≈4.50 km/s) of the profile with velocity difference about −4% at the top of upper mantle are divided according to the differences
of V
s, γ and σ in different media and structures, also with reference to the information of their neighbouring regions; the existence of
Niujiaqiao-Dongwang high-angle ultra-crustal fault zone is reaffirmed; the properties of low and high velocity blocks (zones)
including the crust-mantle transitionalzone and the boudary indicators of North China rift valley are discussed. A comprehensive
study is conducted on the relation of the interpretation results with earthquakes. It is concluded that the mantle upwarps,
thermal material upwells through the high-angle fault, the primary hypocenter was located at the crust-mantle juncture 30.0∼33.0
km deep, and additional stress excited the M
S=6.8 and M
S=7.2 earthquakes at specific locations around 9.0 km below Niujiaqiao-Dongwang, the earthquakes took place around the high-angle
ultra-crustal fault and centered in the brittle media and rock strata with low γ and low σ values.
This subject is part of the 85-907-02 key project during the “8th Five-Year Plan” from the State Science and Technology Commission. 相似文献
289.
New40Ar/39Ar plateau ages from rocks of Changle-Nanao ductile shear zone are 107.9 Ma(Mus), 108.2 Ma(Bi), 107.1 Ma(Bi), 109.2 Ma(Hb)
and 117.9 Ma(Bi) respectively, which are concordant with their isochron ages and record the formation age of the ductile shear
zone. The similarity and apparent overlap of the cooling ages with respective closure temperatures of 5 minerals document
initial rapid uplift during 107–118 Ma following the collision between the Min-Tai microcontinent and the Min-Zhe Mesozoic
volcanic arc. The40Ar/39 Ar plateau ages, K-Ar date of K-feldspar and other geochronologic information suggest that the exhumation rate of the ductile
shear zone is about 0.18–1.12 mm/a in the range of 107–70 Ma, which is mainly influenced by tectonic extension. 相似文献
290.
杭州地区石笋稳定同位素古气候探索 总被引:1,自引:0,他引:1
用14C测年技术和稳定同位素地球化学古温度方法,对浙江省临安瑞晶洞穴的石笋进行了14C的测年和碳、氢、氧同位素测试,获得5~1万年间杭州地区古气候演化记录、该记录表明,在5~1万年间有三次较明显的周期性古温度变化,最高温度为14.9℃,最低温度为6.6℃,最大温差为8℃左右,平均温差3~5℃。这段时期正处在大理冰期后期,但大理冰期并不是一个持续的低温阶段,它至少有3次温度波动。与我们获得的石笋同位素古温度相一致。另外,我们将5~1万年间杭州地区古气候变化与同期东南沿海的海平面变化进行了对比,在时间上也较为吻合,也就是温度上升、海平面也上升,温度下降、海平面也随之下降 相似文献