金矿床的热液流体特征研究     

王建国  孙丽娜  赵玉山  侯根群  赵纯福 《国土资源》1993,(4)

通过对中国东部金成矿区域地质特征的分析,根据氢氧同位素及流体包裹体数据特征,表明中国东部金矿床成矿流体主要来自大气降水,其次为变质作用过程释放的水和岩浆分异水;成矿金属组分主要来自太古宙变质岩系。  相似文献   

八家子铅锌矿区吴家屯矿床矿物特征及银赋存状态     

王树华 《国土资源》1992,(2)

八家子铅锌矿区吴家屯矿床是燕山期形成的热液充填交代脉状铅锌矿床。矿床中除铅锌矿外还伴生有银、硫、铜、锰等多种有益元素。银主要呈微粒自然银、辉银矿、金银矿、银黝铜矿、黝锑银矿、硫砷铜银矿、含碲银矿物等产出,并呈包裹体产于方铅矿、闪锌矿、黄铁矿、黄铜矿、石英等矿物中,或充填于这些矿物的裂隙及晶隙中。少部分银则以类质同象形式存在于方铅矿、黄铁矿矿物中。  相似文献   

Seasonal evolution of the transverse thermohaline asymmetry in the Ria de Pontevedra (northwestern Spain)     

M. deCastro  M. Gmez-Gesteira  I. lvarez  R. Prego 《Estuarine, Coastal and Shelf Science》2006,70(4):673

A quasi-permanent transverse asymmetry in the thermohaline properties of the Ria de Pontevedra (northwestern Spain) was measured from October 1997 to October 1998 during 23 cruises. On average, the density increased form north to south. This asymmetry was maintained by salinity during the wet season, and by salinity and temperature during the dry season. The density difference between coasts (Δσ_t = σ_tsouth − σ_tnorth) and the river discharge were positively correlated (correlation coefficient, approximately 0.6) throughout the year. The density difference was negatively correlated with the upwelling index during the wet season (correlation coefficient, approximately −0.45) and positively correlated during the dry season (correlation coefficient, approximately 0.55).  相似文献   

黄河三角洲桩西101站潮沟地貌形态及其水动力学研究   总被引：6，自引：1，他引：6  

尹延鸿  成国栋  范顺庭  王玉荣  朱兰部 《海洋科学》1997,21(5):46-49

在潮沟下游，横跨且生趣与潮沟的横断面设了５个观测站，进行了２４ｈ的水动力测量。结果表明，涨落潮流速流向不对称，在潮沟内，涨落潮流流速差别很大，涨潮流流速最大为９ｃｍ／２，而落潮流流速最大可达３８ｃｍ／ｓ。据推测，潮沟内之所以落潮流流速明显大于涨潮流流速，可能是由于潮沟与岸线斜交有关。  相似文献   

规则波在缓坡上变形与破碎数值分析     

李玉成  肖辉 《海洋工程》2007,25(1):27-34

通过在二维数值水槽内用边界元法直接求解Laplace方程,对规则波在缓坡上的变形及破碎进行了数值计算。分析了不同底坡及采用不同底摩阻系数时规则波的破碎特征,并对规则波破碎的极限坡度进行了研究。重点分析了规则波破碎时海底坡度、底摩阻系数及波形不对称性对破碎指标的影响。  相似文献   

Undular tidal bore dynamics in the Daly Estuary, Northern Australia   总被引：7，自引：0，他引：7  

Eric Wolanski  David Williams  Simon Spagnol  Hubert Chanson 《Estuarine, Coastal and Shelf Science》2004,60(4):629-636

Measurements in the macro-tidal Daly Estuary show that the presence of an undular tidal bore contributed negligibly to the dissipation of tidal energy. No recirculation bubble was observed between a trough and the following wave crest in the lee waves following the undular bore. This differs to stationary undular bores in laboratory experiments at larger Froude numbers where a recirculation bubble exists. Secondary motions and the turbulence generated by the undular bore had no measurable influence on the sediment transport. This situation contrasts with the intense sediment resuspension observed in breaking tidal bores. The tidally averaged sediment budget in the Daly Estuary was controlled by the asymmetry of tidal currents. The undular bore may widen the river by breaking along the banks that it undercuts, leading to bank slippage. A patch of river-wide macro-turbulence of 3-min duration occurred about 20 min after the passage of the bore during accelerating tidal currents.  相似文献   

冲绳海槽浮岩包裹体的测温试验   总被引：3，自引：2，他引：3  

翟世奎  张杰  张明书  于增慧 《海洋与湖沼》2001,32(1):67-73

对浮岩中斜长石斑晶中的包裹体及玻璃基质中的包裹体首先进行双面光薄片的镜下观察，然后进行了系统的均化法与爆裂法测温试验。观察与试验结果表明：(1)斜长石中的包裹体均为玻璃质+气泡的两相包裹体，未发现气—液包裹体。固化包裹体为玻璃质，非晶质的固化包裹体外即是大量的气泡，特别是基质当中气泡更为发育，说明熔浆中含有丰富的挥发性组分，同时也说明包裹体形成于较浅的地质条件下。(2)长石中包裹体的均化温度不受包裹体特征不同的影响，均化温度分布范围从910—1250℃，峰值明显，计算的均化温度为Tz=(1081.4±177.9)℃，但还存在有高于1250℃的均化温度峰。包裹体均化法测试结果说明浮岩中斜长石的形成过程至少有两个阶段：第一阶段的岩浆温度在1200—1300℃左右，在此温度下形成的是An值较高的基性斜长石，同时结晶的还有辉石等矿物，斜长石结晶第二个阶段时的熔浆温度在1100℃以下，这一阶段持续的时间长，跨越的温度范围大，应是岩浆在近地表和岩浆喷出过程中的岩浆快速冷却期，同时伴随有矿物大规模晶出。(3)包裹体中的气相部分均聚合成圆形或近圆形，说明温度下降速度较快。斑晶斜长石中部分包裹体与基质玻璃中包裹体的形成温度是连续变化的，这一事实应该与冲绳海槽特殊的地质条件有关  相似文献   

珠江河口虎门的地貌动力学研究     

唐兆民  倪培桐  任杰  吴超羽 《热带海洋学报》2007,26(2):34-37

以野外现场调查、数值模拟和前人研究成果综合分析虎门的地貌动力学特征。因峡口上、下游水域开阔,涨落潮过程中发育着强大的双向不对称射流系统;由于峡口区流速最大,发育着冲刷深槽,而峡口的上、下游因流速降低,泥沙有规律地沉积,形成了涨潮三角洲与落潮三角洲堆积体,出现纵向上“马鞍”形断面特征和横向上“槽-脊-滩”的地貌特征,与其动力特征相适应。  相似文献   

Sulfide evolution in high-temperature to ultrahigh-temperature metamorphic rocks from Lützow–Holm Complex, East Antarctica     

T. Kawakami  D.J. Ellis  A.G. Christy 《Lithos》2006,92(3-4):431-446

The high-temperature (HT) to ultrahigh-temperature (UHT) metamorphic rocks from Lützow–Holm Complex, East Antarctica show a systematic difference between sulfide assemblages in the rock matrix and those found as inclusions in the silicates stable in high-temperatures. Matrix sulfides are commonly pyrite with or without pentlandite and chalcopyrite. On the other hand, inclusion sulfides are pyrrhotite with or without pentlandite and chalcopyrite lamellae. When recalculated into integrated single-phase sulfide compositions, inclusion sulfides from the UHT region showed a wider range of solid–solution composition than the inclusion sulfides from the HT region. The host minerals of the sulfides with extreme solid–solution compositions are those stable at the peak of metamorphism such as orthopyroxene and garnet. One of the most extreme ones is included in orthopyroxene coexisting with sillimanite ± quartz, which is the diagnostic mineral assemblage of UHT metamorphism. These observations suggest that sulfide inclusions preserve their peak metamorphic compositions. Pyrrhotite did not revert to pyrite because of the closed system behavior of sulfur in inclusion sulfides. On the other hand, in the rock matrix where the open system behavior of sulfur is permitted, original sulfides were partly to completely altered by the later fluid activity.  相似文献   

DENDROGEOMORPHOLOGICAL ANALYSES ON EXPOSED ROOTS ALONG TWO MOUNTAIN HIKING TRAILS IN THE CENTRAL ITALIAN ALPS     

MANUELA PELFINI  MAURIZIO SANTILLI 《Geografiska Annaler: Series A, Physical Geography》2006,88(3):223-236

ABSTRACT. Mountain landscapes show rapid evolution, especially at high altitudes, in response to current climate changes. In addition, the greater number of routes and trails made available and the increase in tourism have caused some impacts on mountain areas. Gradual soil erosion has been observed along some hiking trails, with the latter tending to deepen, and with stronger erosion where the trail cuts the slope. Where trails cross forested areas, trees can suffer root damage from foot trampling as roots become exposed. A dendrogeomorphological study was conducted on trees along two hiking trails in upper Valtellina (Italian Alps). On the first trail, in Valle dei Forni, European larches and stone pines, mostly with exposed roots, were sampled. A mean erosion rate of 2.7 mm/a, related to deepening of the footpath, was obtained, and various degrees of root growth disturbance along the trail were observed. In particular, the growth of many sampled roots shows an increase in ring width corresponding with the moment when root exposure occurred, followed, after 3–5 years, by rapid growth suppression. The exposure of many roots has taken place since the 1980s. No significant variations in stem growth were observed, even when there were exposed and damaged roots. Along the second trail, in Valle Alpisella, exposed roots of mountain pines were analysed. A mean erosion rate of 3.2–3.7 mm/a, related to the escarpments bordering the footpath, was obtained, while no significant changes were detected in root growth.  相似文献