Triassic Nb-enriched basalts, magnesian andesites, and adakites of the Qiangtang terrane (Central Tibet): evidence for metasomatism by slab-derived melts in the mantle wedge

New chronological, geochemical, and isotopic data are reported for Triassic (219–236 Ma) adakite-magnesian andesite-Nb-enriched basaltic rock associations from the Tuotuohe area, central Qiangtang terrane. The adakites and magnesian andesites are characterized by high Sr/Y (25–45), La/Yb (14–42) and Na₂O/K₂O (12–49) ratios, high Al₂O₃ (15.34–18.28 wt%) and moderate to high Sr concentrations (220–498 ppm) and ε_ND (t) (+0.86 to +1.21) values. Low enrichments of Th, Rb relative to Nb, and subequal normalized Nb and La contents, and enrichments of light rare earth elements combine to distinguish a group of Nb-enriched basaltic rocks (NEBs). They have positive ε_ND (t) (+2.57 to +5.16) values. Positive correlations between Th, La and Nb and an absence of negative Nb anomalies on mantle normalized plots indicate the NEBs are products of a mantle source metasomatized by a slab melt rather than by hydrous fluids. A continuous compositional variation between adakites and magnesian andesites confirms slab melt interaction with mantle peridotite. The spatial association of the NEBs with adakites and magnesian andesites define an “adakitic metasomatic volcanic series” recognized in many demonstrably subduction-related environments (e.g., Mindanao arc, Philippines; Kamchatka arc, Russia; and southern Baja California arc, Mexico). The age of the Touhuohe suite, and its correlation with Triassic NEB to the north indicates that volcanism derived from subduction-modified mantle was abundant prior to 220 Ma in the central Qiangtang terrane.     

青岛市水环境污染及其防治对策

通过分析近几年青岛市地表，地下水水质监测资料，总结水环境污染地区分布规律，摸清水环境污染形成原因，对当前防污治污工作提出了对策建议。     

Climate change in Mt. Qomolangma region since 1971

Using monthly average, maximum, minimum air temperature and monthly precipitation data from 5 weather stations in Mt. Qomolangma region in China from 1971 to 2004, climatic linear trend, moving average, low-pass filter and accumulated variance analysis methods, the spatial and temporal patterns of the climatic change in this region were analyzed. The main findings can be summarized as follows: (1) There is obvious ascending tendency for the interannual change of air temperature in Mt. Qomolangma region and the ascending tendency of Tingri, the highest station, is the most significant. The rate of increasing air temperature is 0.234 oC/decade in Mt. Qomolangma region, 0.302 oC/decade in Tingri. The air temperature increases more strongly in non-growing season. (2) Compared with China and the global average, the warming of Mt. Qomolangma region occurred early. The linear rates of temperature increase in Mt. Qomolangma region exceed those for China and the global average in the same period. This is attributed to the sensitivity of mountainous regions to climate change. (3) The southern and northern parts of Mt. Qomolangma region are quite different in precipitation changes. Stations in the northern part show increasing trends but are not statistically significant. Nyalam in the southern part shows a decreasing trend and the sudden decreasing of precipitation occurred in the early 1990s. (4) Compared with the previous studies, we find that the warming of Mt. Qomolangma high-elevation region is most significant in China in the same period. The highest automatic meteorological comprehensive observation station in the world set up at the base camp of Mt. Qomolangma with a height of 5032 m a.s.l will play an important role in monitoring the global climate change.     

参量阵浅地层剖面测量技术 在近岸海洋工程的应用效果

介绍了海底浅地层声学探测技术的发展情况, 简述了新型参量阵声纳探测的原理和特点, 通过SES-96参量阵测深或浅地层剖面系统在山东半岛海区的应用实例, 对此新型参量阵声纳技术的应用效果进行了分析评价。     

滇黔桂盆地及其邻区石炭纪至二叠纪层序地层格架及三级海平面变化的全球对比

属于被动大陆边缘裂谷盆地的滇黔桂盆地，自加里东运动之后，泥盆纪开始拉开，整个晚古生代延续发展。受同生断裂的控制，在深水盆地中发育大小不等的孤立碳酸盐台地，因而在滇黔桂盆地及其邻区形成特殊的“台-盆-丘-槽”的古地理格局。对不同古地理背景下的典型剖面进行三级层序划分并对其进行空间追索和对比，在滇黔桂盆地及其邻区的石炭纪和二叠纪地层中可以识别出12个三级层序，相当于晚古生代25个三级沉积层序(2-5Ma；SQ1至SQ25)中的SQ24至SQ25；以地层记录中的的两种相变面和两种穿时性为基本要素，可以建立研究区石炭系和二叠系的层序地层格架；层序地层格架反映了三级层序的基本特征：空间上相序的有序性和时间上环境变化的同步性。研究区的石炭系和二叠系，主要为一套碳酸盐岩地层，其中在连陆台地上发育3套煤系地层，它们分别组成石炭纪三级层序SQ15跨系的三级层序SQ19的HST以及二叠纪吴家坪期的三级层序SQ24；而且在连陆台地边缘和孤立台地上，于阳新世的茅口亚世以及乐平世的长兴期发育海绵生物礁，海绵生物礁分别构成了以下二叠系三级层序即阳新世的SQ22和SQ23以及长兴期的SQ25。3套煤系地层和两套海绵生物礁的发育，使研究区的石炭系和二叠系形成了一个与欧美地区完全不同的层序地层序列。在研究区石炭系和二叠系所识别出的12个三级层序中，石炭纪一二叠纪船山世地层可以划分出6个三级层序。这种划分与Busch等对北美相同层位的划分相似，也就是说该6个三级层序的形成时限大于10Ma；较长的形成时限可能反映了形成在联合古陆汇聚时期即全球构造相对稳定时期三级海平面变化的一个特性。因此，研究区的石炭系和二叠系所识别和划分出的12个三级层序，其数量比Ross和Ross(1985)对欧美地区石炭系和二叠系所划分出的50多个三级层序要少得多。     

内蒙古喀喇沁早白垩世橄辉云煌岩岩筒

探寻地幔物质上涌的通道口，是大陆岩石圈研究所感兴趣的，它将为人们提供更多的岩石圈深部信息。本文报道的是在内蒙古喀喇沁黑龙潭火山颈中发现的橄辉云煌岩，其K-Ar同位素年龄为124Ma。火山活动明显受到中生代构造活动控制。火山岩的元素地球化学特征反映岩浆来自富集地幔，在源区存在陆壳的混染作用。     

鲁东南岚山头超高压变质岩流体包裹体特征与板片折返史

鲁东南岚山头含柯石英榴辉岩主要产于花岗质片麻岩内,是苏鲁超高压变质带主要榴辉岩体密集分布区之一。流体包裹体研究表明,榴辉岩矿物及细脉石英中捕获有四种类型包裹体:在超高压-高压榴辉岩相条件下捕获的 N_2±CO_2包裹体;在高压榴辉宕重结晶阶段被捕获的 CO_2-H_2O 包裹体和含子矿物高盐度 H_2O 溶液包裹体:在超高压岩石折返过程中的最晚(角闪岩相退变质甚至更晚)阶段捕获的低盐度 H_2O 溶液包裹体。利用榴辉岩矿物及脉体石英中捕获的流体包裹体相互期次关系,可以对本区超高压变质作用板片折返过程中的流体演化史进行重建。     

海底热液硫化物矿体内部流体混合过程的数值模拟:以大西洋TAG热液活动区为例

大型海底热液硫化物矿体的形成机制是涉及多种控制因素的复杂地质过程,其中热液流体同海水的混合扮演着重要角色。大洋钻探计划(ODP)资料表明在大西洋TAG区热液硫化物矿体内部,热液流体同经过改造的海水之间发生着广泛的混合作用,这个过程在很大程度上控制着海底热液硫化物矿体的内部结构和化学组成。以TAG热液硫化物矿体为例,利用数值模拟方法模拟了热液流体与经过不同程度改造的海水的混合过程,试图探讨海水与热液流体混合在热液硫化物矿体形成中的作用。模拟计算结果表明:(1)来自矿体深部的热液流体与经围岩加热的下渗海水的混合是造成TAG热液活动区硬石膏大量沉淀的重要原因;(2)在热液流体与海水的混合过程中,混合流体的化学性质和矿物沉淀情况在330~310℃上下发生了较大变化,330~310℃是一个特殊的温度区域;(3)利用数值计算结果探讨了TAG热液活动区不同区块(TAG-1,TAG-2和TAG-5等)的流体混合作用和热液活动过程。     

Argo floats revealing bimodality of large-scale mid-depth circulation in the North Atlantic

Analysis of Argo float trajectories at 1 000 m and temperature at 950 m in the North Atlantic between November 2003 and January 2005 demonstrates the existence of two different circulation modes with fast transition between them. Each mode has a pair of cyclonic - anticyclonic gyres. The difference is the location of the cyclonic gyre. The cyclonic gyre stretches from southeast to northwest in the first mode and from the southwest to the northeast in the second mode. The observed modes strongly affect the heat and salt transport in the North Atlantic. In particular, the second mode slows down the westward transport of the warm and saline water from the Mediterranean Sea.     

GPS导航对抗策略与技术分析

阐述了导航对抗的基本概念和要素,分析了导航对抗中的主要攻防策略,研究了用于导航对抗的干扰及抗干扰技术,总结了GPS为增强系统安全性所进行的改进和完善的主要方面,并介绍了一些适合应用的导航对抗技术手段。