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91.
康定杂岩时代及成因探讨   总被引:21,自引:0,他引:21  
胥德恩  陈友良 《地质论评》1995,41(2):101-111
康定杂岩是康滇地轴上一套复杂岩系,由紫苏辉长质暗色杂岩、英云闪长质浅色杂岩及复成分混合杂岩构成。岩石结构构构造,铀、钍及稀土特表明,主体为岩浆杂岩,包含大量具层状痕迹的变质杂岩。大量的锆石U-Pb年龄及其它同位素年龄表明,岩浆岩属晋宁-澄江期。变质杂岩时代与河口群相当。  相似文献   
92.
时间标度计算表明,西北太平洋热带气旋路径是一个无标度性的系统,其关联方差谱遵从频率的-2 ̄-3次方幂律,不同背景下的路径系统均如此。由此得到的不同季节、不同地域的热带气旋路径可预报时间尺度基本上为3 ̄4d,但异常热带气旋路径的可预报时间尺度则为1 ̄2d。  相似文献   
93.
采用T21L5大气环流模式,详细探讨了冬季西北太平洋海表温度异常对太平洋风暴轴的影响。结果表明:冬季西北太平洋暖海表温度异常能显著增强异常区北侧及下游地区的斜压性,天气尺度扰动方差、扰动动能以及涡动热量通量等也在此风暴轴入口区得到增强,由此揭示出外热源强迫对太平洋风暴轴的维持和发展起重要作用。  相似文献   
94.
石英裂变径迹蚀刻条件的对比实验研究   总被引:5,自引:0,他引:5  
通过 40%的 HF溶液、KOH饱和溶液和 19 mol/L的 NaOH溶液这三种常用方法对大、小颗粒石英进行裂变径迹蚀刻实验的对比发现,用环氧树脂固定的小颗粒石英样品,不宜用 KOH饱和溶液(150 ℃)和 19 mol/L的 NaOH溶液(沸点,约 120 ℃)作为裂变径迹的蚀刻剂,宜用 40%的 HF溶液;三种方法均适宜于大颗粒石英,但不同的蚀刻方法蚀刻效率不同, 40%的 HF溶液(29 ℃)的蚀刻效率最高,且操作简单、安全性高.40%的 HF溶液最佳蚀刻时间为: 温度在 4 ℃左右(冬季)时为 40 min,温度在 29 ℃左右(夏季)时为 30 min,可在全年室内常温条件下操作.  相似文献   
95.
The Andhra severe cyclonic storm (2003) is simulated to study its evolution, structure, intensity and movement using the Penn State/NCAR non-hydrostatic mesoscale atmospheric model MM5. The model is used with three interactive nested domains at 81, 27 and 9 km resolutions covering the Bay of Bengal and adjoining Indian Peninsula. The performance of the Planetary Boundary Layer (PBL) and convective parameterization on the simulated features of the cyclone is studied by conducting sensitivity experiments. Results indicate that while the boundary layer processes play a significant role in determining both the intensity and movement, the convective processes especially control the movement of the model storm. The Mellor-Yamada scheme is found to yield the most intensive cyclone. While the combination of Mellor-Yamada (MY) PBL and Kain-Fritsch 2 (KF2) convection schemes gives the most intensive storm, the MRF PBL with KF2 convection scheme produces the best simulation in terms of intensity and track. Results of the simulation with the combination of MRF scheme for PBL and KF2 for convection show the evolution and major features of a mature tropical storm. The model has very nearly simulated the intensity of the storm though slightly overpredicted. Simulated core vertical temperature structure, winds at different heights, vertical winds in and around the core, vorticity and divergence fields at the lower and upper levels—all support the characteristics of a mature storm. The model storm has moved towards the west of the observed track during the development phase although the location of the storm in the initial and final phases agreed with the observations. The simulated rainfall distribution associated with the storm agreed reasonably with observations.  相似文献   
96.
近圆轨道遥感卫星星下点轨迹的计算   总被引:3,自引:0,他引:3  
根据遥感卫星轨道的特点,提出了计算近圆轨道卫星星下点轨迹的算法,并对其进行精度评估。结果表明这种算法是快捷和有效的,能够满足卫星规划阶段对轨道精度的要求。  相似文献   
97.
龙胜地区镁铁质侵入体:年龄及其地质意义   总被引:26,自引:0,他引:26       下载免费PDF全文
对镁铁质侵入体进行了单颗粒锆石U-Pb年代学和Sm-Nd同位素示踪研究。结果表明:镁铁质侵入体是起源于长期亏损地幔源区的岩浆在760Ma侵位结晶的产物,其侵位过程中遭受地壳物质的混染。该年龄结果限定了丹洲群地层的沉积上限年龄,并为龙胜地区不存在蛇绿岩套的认识提供重要的年代学制约。镁铁质岩浆的形成、侵位可能与Rodinia超大陆~825Ma裂解之后的另一次裂解事件相联系。  相似文献   
98.
一种公平技术评分方法在台风业务预报评估中的应用   总被引:2,自引:0,他引:2  
将离散变量分级预报的公平技术评分方法引入台风路径业务的预报评估中,对1989-1991年的台风业务预报作评估试验,结果表明,该方法量客观,不但可用于台风分类预报评估,也可对台风移向移速预报进行客观评估。  相似文献   
99.
Abstract Apatite and zircon fission track ages from Ryoke Belt basement in northeast Kyushu show late Cretaceous, middle to late Eocene, middle Miocene and Quaternary groupings. The basement cooled through 240 ± 25°C, the closure temperature for fission tracks in zircon, mainly during the interval 74-90 Ma as a result of uplift and denudation, the pattern being uniform across northeast Kyushu. In combination with published K-Ar ages and the Turonian-Santonian age of sedimentation in the Onogawa Basin, active suturing along the Median Tectonic Line from 100-80 Ma, at least, is inferred. Ryoke Belt rocks along the northern margin of Hohi volcanic zone (HVZ) cooled rapidly through ∼100°C to less than 50°C during the middle Eocene to Oligocene, associated with 2.5-3.5 km of denudation. The timing of this cooling follows peak heating in the Eocene-Oligocene part (Murotohanto subbelt) of the Shimanto Belt in Muroto Peninsula (Shikoku) inferred previously, and coincides with the 43 Ma change in convergence direction of the Pacific-Eurasian plate and the demise of the Kula-Pacific spreading centre. Ryoke Belt rocks along the southern margin of HVZ have weighted mean apatite fission track ages of 15.3 ± 3.1 Ma. These reset ages are attributed to an increase in geothermal gradient in the middle Miocene combined with rapid denudation and uplift of at least 1.4 km. These ages indicate that heating of the overriding plate associated with the middle Miocene start of subduction of hot Shikoku Basin lithosphere extended into the Ryoke Belt in northeast Kyushu. Pleistocene apatite fission track ages from Ryoke Belt granites at depth in the centre of HVZ are due to modern annealing in a geothermal environment.  相似文献   
100.
The Qingchengzi orefield is a large polymetallic ore concentration area in the Liaodong peninsula,northeastern China,that includes twelve Pb-Zn deposits and five Au-Ag deposits along its periphery.The ore-forming age remains much disputed,which prevents the identification of the relationship between the mineralization and the associated magmatism.In this paper,we quantitatively present the feasibility of making ore mineral ~(40)Ar/~(39)Ar dating and report reliable ~(40)Ar/~(39)Ar ages of lamprophyre groundmass,K-feldspar and sphalerite from the Zhenzigou deposit.Direct and indirect methods are applied to constrain the timing of mineralization,which plays a vital role in discussing the contribution of multistage magmatism to ore formation.The low-potassium sphalerite yielded an inverse isochron age of 232.8±41.5 Ma,which features a relatively large uncertainty.Two lamprophyre groundmasses got reliable inverse isochron ages of 193.2±1.3 Ma and 152.3±1.5 Ma,respectively.K-feldspar yielded a precise inverse isochron age of 134.9±0.9 Ma.These four ages indicate that the mineralization is closely associated with Mesozoic magmatism.Consequently,regarding the cooling age of the earliest Mesozoic Shuangdinggou intrusion(224.2±1.2 Ma)as the initial time of mineralization,we can further constrain the age of the sphalerite to 224–191 Ma.These new and existing geochronological data,combined with the interaction cutting or symbiotic relationship between the lamprophyre veins and ore veins,suggest that the Pb-Zn-Au-Ag mineralization in the Qingchengzi orefield mainly occurred during three periods:the late Triassic(ca.224–193 Ma),the late Jurassic(ca.167–152 Ma)and the early Cretaceous(ca.138–134 Ma).This polymetallic deposits are shown to have been formed during multiple events coinciding with periods of the Mesozoic magmatic activity.In contrast,the Proterozoic magmatism and submarine exhalative and hydrothermal sedimentation in the Liaolaomo paleorift served mainly to transport and concentrate the ore-forming substances at the Liaohe Group with no associated Pb-Zn-Au-Ag mineralization.  相似文献   
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