浅论新疆海相火山热水沉积矿床的分带及其找矿意义   总被引：9，自引：0，他引：9  

王永新  田培仁 《地质与勘探》2003,39(4):6-11

新疆海相火山热水沉积矿床，一般在时间上没有明显的集中生长期。空间上依附于活动大陆边缘火山岛弧带，它在区域上和矿床本身具有矿种转化、类型转换、配套与分带特征。以块状氧化物、块状碳酸盐和块状硫化物转换序次来研究该类矿床。利用铁木尔特铅锌矿上部铅锌下部铜金，预须开普台铁矿上铁下铜；莫托沙拉铁锰矿上锰下铁中间铅锌重晶石等矿种转化规律和由块状氧化物和块状碳酸盐向块状硫化物成生过渡特点，预测诸如蒙库铁矿、赤龙峰火山盆地中铁矿和喀喇昆仑山各铁矿床(点)外围与深部转换、发展成为铜金矿的成矿前景。  相似文献   

Seismic scattering at the top of the mantle Transition Zone     

H. Thybo  L. Nielsen 《Earth and Planetary Science Letters》2003,216(3):259-269

We document strong seismic scattering from around the top of the mantle Transition Zone in all available high resolution explosion seismic profiles from Siberia and North America. This seismic reflectivity from around the 410 km discontinuity indicates the presence of pronounced heterogeneity in the depth interval between 320 and 450 km in the Earth’s mantle. We model the seismic observations by heterogeneity in the form of random seismic scatterers with typical scale lengths of kilometre size (10-40 km by 2-10 km) in a 100-140 km thick depth interval. The observed heterogeneity may be explained by changes in the depths to the α-β-γ spinel transformations caused by an unexpectedly high iron content at the top of the mantle Transition Zone. The phase transformation of pyroxenes into the garnet mineral majorite probably also contributes to the reflectivity, mainly below a depth of 400 km, whereas we find it unlikely that the presence of water or partial melt is the main cause of the observed strong seismic reflectivity. Subducted oceanic slabs that equilibrated at the top of the Transition Zone may also contribute to the observed reflectivity. If this is the main cause of the reflectivity, a substantial amount of young oceanic lithosphere has been subducted under Siberia and North America during their geologic evolution. Subducted slabs may have initiated metamorphic reactions in the original mantle rocks.  相似文献   

答“对秦岭奥长环斑花岗岩质疑”   总被引：8，自引：1，他引：8  

卢欣样王晓霞  肖庆辉尉向东 董有 《地质论评》2003,49(2):146-154

环斑花岗岩是一种特殊结构的花岗岩类，并且多数产在元古宙克拉通中。笔者曾报道了在秦岭造山带中发育有印支期具有环斑结构的花岗质岩石。“对秦岭奥长环斑花岗岩质疑”一文认为它们不是环斑花岗岩，并引用Ramo的图表来说明自己的观点。本文将从以下几方面进行讨论：秦岭环斑花岗岩的研究历史；环斑花岗岩的定义；世界上环斑花岗岩的成因类型；秦岭环斑花岗岩的副矿物及铁镁含量和环斑钾长石特征；秦岭环斑花岗岩与基性岩共存等。本文还论证了秦岭环斑花岗岩不同于元古宙非造山环斑花岗岩，而是一种造山型的环斑花岗岩，其形成于后造山环境，是挤压（造山）向拉张（稳定）转折时期的产物。最后对研究秦岭环斑花岗岩的几个理论问题进行了探讨。  相似文献   

Numerical models of tectonic deformation at the Baltica–Avalonia transition zone during the Paleocene phase of inversion     

Anna Maria Marotta  Roberto Sabadini 《Tectonophysics》2003,373(1-4):25

Predictions from dynamic modelling of the lithospheric deformation are presented for Northern Europe, where several basins underwent inversion during the Late Cretaceous and Early Cenozoic and contemporary uplift and erosion of sediments occurred. In order to analyse the evolution of the continental lithosphere, the equations for the deformation of a continuum are solved numerically under thin sheet assumption for the lithosphere. The most important stress sources are assumed to be the Late Cretaceous Alpine tectonics; localized rheological heterogeneities can also affect local deformation and stress patterns. Present-day observations available in the studied region and coming from seismic structural interpretations and stress measurements have been used to constrain the model. Our modelling results show that lateral variation in lithospheric strength below the basin systems in Central Europe strongly controls the regional deformation and the stress regime. Furthermore, we have demonstrated that the geometry of the boundary between Baltica and Avalonia, together with different rheological characteristics of the two plates, had a crucial role on local crustal deformation and faulting regime resulting in the Baltica–Avalonia transition zone from the S–N Alpine convergence.  相似文献   

The effects of the spinel—garnet phase transition on the formation of rifted sedimentary basins     

Tadashi Yamasaki  Masao Nakada 《Geophysical Journal International》1997,130(3):681-692

We have examined the effects of the spinel-garnet phase transition on subsidence of extensional sedimentary basins. For a constant positive Clapeyron slope ( dP/dT ), the phase boundary moves downwards in the syn-rift and upwards in the post-rift phase. For a non-linear Clapeyron curve ( dP/dT > 0 above 900°C and dP/dT < 0 below 900°C), theory predicts for the reaction of the spinel-garnet phase transition, the direction of phase boundary movement is dependent on the stretching factor, the position of the Clapeyron curve and the lithospheric thickness. A smaller syn-rift and larger post-rift subsidence are predicted for a deeper phase boundary and a thicker lithosphere. The model with a non-linear Clapeyron curve is applied to the subsidence histories of a young extensional basin (Gulf of Lion) and an old continental margin (eastern Canada). The observed syn-rift uplift and the larger post-rift subsidence can be reasonably explained by this model, where the optimum depth of the phase boundary for eastern Canada (˜90 km) is consistent with the estimate from seismic observations and is larger than that for the Gulf of Lion (˜ 50 km). The depth of the spinel-garnet phase boundary is sensitive to the composition of mantle rocks and increases with the extraction of basaltic components from the lithosphere, compatible with our result that the phase boundary is deeper for an older and thicker lithosphere. Thus the surface movement associated with the rifting for these areas may reflect the chemical evolution of the continental lithosphere.  相似文献   

岩浆-流体过渡和阿尔泰三号伟晶岩脉之成因   总被引：13，自引：0，他引：13  

卢焕章  王中刚  李院生 《矿物学报》1996,16(1):1-7,T002

本文对新疆阿尔泰可可托海的三号伟晶岩形成的物理化学条件、特别是流体-熔融包裹体进行了研究，证明岩浆的确可以分出热液，对于三号伟晶岩脉来说，这种热液组分主要是NaCl－CO2－H2O流体。  相似文献   

计算机多媒体技术在地学领域中的某些应用     

陈源  袁伟  刘智洋 《地质科技情报》1997,(Z1)

结合地质工作特点，概述了计算机多媒体技术在地质科研、地质教育、成果汇报演示以及地质信息管理方面的应用成果，展示了多媒体技术在地学领域中的应用前景。  相似文献   

假玻状岩研究的新进展   总被引：1，自引：0，他引：1  

张桂林 《地质科技情报》1997,16(2):24-28

综述了假玻状岩研究的主要进展，假玻状岩形成的磨擦熔融机制与机械磨碎机制实际上不是过去所认为的是两种互相排斥的机制，而是在假玻状岩形成过程中两个密切相关的阶段，磨碎作用是熔融发生的必要的前提条件；假玻状岩不仅可以形成于脆性域（与碎裂岩相关），而且可以形成于脆韧性过渡区（与糜棱岩相关），形成的最大深度可达１８ｋｍ；假玻状岩是围岩中矿物选择性熔融的产物，矿物优先熔融的顺序（从易到难）为：层状硅酸盐、链状  相似文献   

STUDY ON THE VARIATION IN THE CONFIGURATION OF SUBTROPICAL ANTICYCLONE AND ITS MECHANISM DURING SEASONAL TRANSITION-PART Ⅱ:SEASONAL TRANSITION INDICES OVER THE ASIAN MONSOON REGION          下载免费PDF全文

MAO Jiangyu  WU Guoxiong  LIU Yimin 《Acta Meteorologica Sinica》2004,18(1):17-32

Based on the studies in Part Ⅰ (see Mao et al.2003),this paper further examines the relationship between the Asian summer monsoon onset and variation in meridional position of the warm temperature ridge with a zonal orientation in mid-upper troposphere.During the Asian monsoon bursting consequentially over the Bay of Bengal,South China Sea,and South Asia,in addition to the reversal of winds in the lower and upper troposphere and deep convection before and after the onset,the atmospheric meridional temperature gradient (MTG) in the vicinity of the ridge-surface of subtropical high (WEB defined in Part Ⅰ) exhibits a significant reversal.Since the establishment of temperature structure with higher over north than over south of the WEB in the mid-upper troposphere (200-500 hPa) characterizes the collective essential that the Asian summer monsoon bursts over different areas,the MTG in mid-upper troposphere,based on the thermodynamics associated with the seasonal transition,should be a reasonable index to measure the Asian monsoon onset.The definition for onset date is proposed,and the time series of onset date for different sections are determined.As compared with the onset dates determined by other indices such as 850-hPa zonal wind and OLR.correlation analyses indicate that the 850-hPa zonal wind is only regional index,but the MTG index is applicable universally to the Asian monsoon regime.  相似文献   

多年冻土区路桥过渡段的一种新结构     

刘建坤  鲍维猛  黎明  葛建军 《冰川冻土》2004,26(Z1):210-214

The design of roadbed-abutment transition part is always a challenging problem in transportation engineering, especially in permafrost distribution zone. A new type of roadbed-abutment transition part on permafrost was presented, and long-term observation was conducted for the deformation and the thermal regime of a roadbed-abutment transition part in the constructing Qinghai-Tibet Railway. In this paper, a new structure was presented and the observed settlements both in the subgrade and the base and its dependency with the thermal regime (permafrost table) were analyzed. In conclusion the roadbed-a-butment transition method for permafrost distribution zone was evaluated.  相似文献