排序方式: 共有44条查询结果,搜索用时 78 毫秒
1.
2.
通过对下四种环境中岩浆混染作用的实验研究:(1)俯冲板块之上;(2)地幔-陆壳边界界之下和(3)地幔-际壳边界之上;(4)浅部地壳内。用含H2O硅质熔体橄榄岩或角闪岩之间反应的一系列清楚的边界确定了;(1)混染熔体内的扩散断面和(2)二种物质之质的结晶反应带。由含H2O的橄榄岩-英云闪长岩-花岗岩混合物确定了一些相界,这些相界能区分从俯冲板块中产生的并经过地幔上升的熔体的混染程度和与橄榄岩(如堆积 相似文献
3.
In examining ship-mediated biological invasions, most research and treatment development has focused on ballast water. Another vector that has gained attention recently is vessels arriving in a "no ballast on board" (NOBOB) condition. Such ships retain relatively small, unpumpable volumes of water and sediment in their ballast tanks. Nonetheless, these unpumpable portions can represent great ecological risk. This scenario is relevant in the Great Lakes, which have experienced a dramatic series of introductions, despite most vessels arriving there as NOBOBs since 1994. We examined shipping patterns of NOBOBs arriving to lower Chesapeake Bay to begin evaluating their risk of biopollution. Only 14% of ships arrive as NOBOBs, and of those, 17% depart to another port in the upper bay. Most NOBOBs arrive from or leave for other US ports; proximate trans-Atlantic crossings are few. Given the nature of their operations, we conclude NOBOBs may represent a risk for aquatic nuisance species invasions to Chesapeake Bay. 相似文献
4.
滇西南云县三叠纪火山岩组合及系列的厘定及其构造意义 总被引:3,自引:2,他引:1
本文重新厘定了云县三叠纪火山岩的组合和系列,识别了4个层位中的酸性熔结凝灰岩,重新划分了火山喷发旋回和韵律。中三叠统忙怀组(T2m)为富硅富铝高钾流纹质火山岩组合,该旋回由5个喷发韵律层组成;上三叠统小定西组(T3x)为高钾玄武岩-钾玄岩-安粗岩及火山碎屑岩组合,该旋回由6个喷发韵律层组成。芒汇河组(T3mh)为钾质粗面玄武岩-高钾流纹质火山岩组合,该旋回由6个喷发韵律层组成。T2m火山岩属碰撞型弧火山岩,T3x和T3mh火山岩属钾玄岩系列火山岩,具有滞后型弧火山岩之属性。 相似文献
5.
对沿南极半岛太平洋边缘的冰川海洋沉积作用进行的研究表明,目前该区域的入海冰川形成的沉积物很少。这与限制融水向峡湾入口输入的副极地气候至极地气候区域有关,但南设得兰群岛除外。与更温暖的阿拉斯加和智利峡湾相比,这里发现的沉积物很薄,多数峡湾的地震反射剖面支持了这种解释。然而,这种假说只是根据南极沿海地区零星的地震覆盖区得出的。因此,就象PalmerDeep地区的内陆架证实的那样,地震资料不能满足第四纪沉积物序列的分辨率。这里,我们提供了南极南Gerlache海峡和Andvord海湾中进行的高分辨率地… 相似文献
6.
火山碎屑岩是介于熔岩和沉积岩之间的过渡类型岩石,岩类复杂。长期以来,火山碎屑岩的分类研究受到了国内外学者的重视,先后提出了火山碎屑物、火山碎屑岩岩性和火山碎屑岩成因分类。虽然目前国际地科联火成岩分类命名委员会确定的火山碎屑物和火碎屑岩岩性分类已得广泛推广,但此分类尚有不足之处。中国学者提出的火山碎屑岩分类时间较早,有自己特色,在一定的范围得到了应用。在此基础上,本文提出了新的火山碎屑物、火山碎屑岩岩性和火山碎屑岩成因分类。火山沉积作用是介于火山学和沉积学之间的边缘研究领域。近20年来,火山沉积作用研究在理论和方法上得到了深化,火山喷发和沉积的物理作用及实验和数值模拟已经成为未来发展的趋势。尽管这样,野外地质和火山碎屑岩的岩性特征,仍是火山碎屑岩成因研究的基础。 相似文献
7.
Several immune parameters were evaluated in two species of mussels (Mytilus californianus and M. galloprovincialis/M. trossulus) as bioindicators of contaminant effects. The mussels were deployed in San Francisco Bay Estuary and a control site at Bodega Marine Laboratory. Assays for phagocytosis and phagocytic index (average number of particles engulfed per hemocyte) were conducted with hemocytes in their own hemolymph-the "Serum" method. The responses were compared with contaminant concentrations in those mussels. For both species, the contaminated South Bay Dumbarton Bridge and Redwood Creek sites had elevated phagocytosis relative to the Bodega control site, indicating contaminant stress. The results also showed that M. californianus had higher percentages of phagocytosis (74%) and a higher phagocytic index (4.6 particles per cell) than those of M. galloprovincialis/M. trossulus (60% phagocytosis and 3.5 particles per cell). As there is a difference in immune response to contaminants, it is suggested that future San Francisco Estuary monitoring should be conducted with endemic M. galloprovincialis/M. trossulus rather than with the currently utilized M. californianus, which is not found in the estuary. 相似文献
8.
英安岩中高压辉石巨晶的发现及其意义 总被引:5,自引:0,他引:5
在吉林省九台市官马山晚侏罗世英安岩中发现了辉石巨晶。研究表明。该巨晶不是英安岩浆的结晶产物,英安岩的岩相关及地球化学特征显示,它是酸性流纹岩浆与基性偏碱性的玄武岩浆经混合作用形成的,辉石巨晶是后一种岩浆在高压条件下结晶的产物,对辉石巨晶的温压计算结果表明,该矿物结晶温度为1276℃,压力为1.27GPa。这一深度可相当于该区软流层的顶界。可以认为,晚侏罗-早白垩世火山岩形成于地壳较厚的环境。 相似文献
9.
湘南中新生代玄武岩岩石学特征 总被引:19,自引:1,他引:19
根据30多个玄武岩体的详细的实际资料,将研究区内中新生代玄武岩划分为5种类型,分属2个岩浆系列,判别出3种原生岩浆。橄榄拉斑玄武岩、白榴碧玄岩和碧玄岩为原生岩浆;碱性橄榄玄武岩和石英拉斑玄武岩为进化岩浆。玄武岩的矿物学和地球化学特征表现出大陆板内玄武岩之属性,是大陆岩石圈小范围热扰动的产物 相似文献
10.
Cato PT 《Soviet geography》1982,23(1):31-48
"Among certain ethnic groups in the USSR, males and females have different levels of retention of the native language. Male and female levels vary inside and outside the home territory depending on the general strength of the language, ethnic rights in the place of residence, and migrant versus non-migrant status. Additional distinctions correspond to cultural divisions, principally Moslem versus non-Moslem." 相似文献