鲁东胶莱盆地青山组火山岩的^40Ar—^39Ar定年——以五莲分岭山火山机构为例

以五莲分岭山火山机构为例，运用高精度的^40Ar－^39Ar定年技术，对胶莱盆地青山组火山岩的形成年龄进行了精确测定。结果表明。青山组第一旋回中偏碱性富钾火山岩的形成年龄为109．9±0．6Ma，第二旋回酸性流纹质火山岩形成年龄为108．2±0．6Ma，据此确定胶莱盆地青山组火山岩应为早白垩世岩浆活动的产物。根据该组火山岩在空间上具有自西向东年龄渐新的演变趋势，表明中生代伊泽奈崎板块向欧亚板块碰撞俯冲应是制约区内火山活动的主要动力因素。     

Population Shrinkage in Resource-dependent Cities in China: Processes,Patterns and Drivers

Resource-dependent cities(RCs)are a vulnerable group of urban settlements that often face population shrinkage;however,population changes in RCs in China are not well understood.This study offers new insight into this matter through a robust analysis that features a longer time scale,a larger sample of RCs,and a finer unit of analysis.It finds new evidence that problems of population shrinkage in RCs are more serious than previous literature has suggested.Approximately 30%of the studied units have experienced either long-term or short-term population shrinkage,and many more are experiencing a slowing down of population growth.Problems are especially common among three types of RCs:the resource-depleted RCs,the forestry-based RCs,and RCs in Northeast China.These results underscore transition policy inadequacies in addressing population loss,and call for a more comprehensive and diversified population policy that tackles the multifaceted factors that contribute to population shrinkage,including lack of industrial support,maladjustment to market oriented reformation,poor urban environment and natural population decline.     

柴达木盆地北缘30Ma左右的去顶剥蚀作用——~(40)Ar/~(39)Ar热年代学定量制约

通过对柴达木盆地北缘两个花岗质岩体的钾长石进行的氩多重扩散域理论 (MDD)模拟及年龄测定 ,得到了这些岩体的冷却历史。结果表明 ,30Ma左右这里曾发生过一次快速冷却事件 (7.5～ 9.4°C Ma) ,表示该地区此时曾发生去顶剥蚀作用 ,是该地区的抬升作用的结果。这可能和阿尔金断裂的走滑活动有关。     

Metamorphic P–T conditions and thermal structure of Chinese Continental Scientific Drilling main hole eclogites: Fe–Mg partitioning thermometer vs. Zr-in-rutile thermometer

Core rocks recovered from the main hole (5158 m deep) of the Chinese Continental Scientific Drilling (CCSD‐MH) project, southern Sulu UHP terrane, east‐central China, consist of eclogites, various gneisses and minor metaperidotite cumulates; this lithological section underwent subduction‐zone UHP metamorphism. Coesite‐bearing eclogites are mainly present between the depths of 100–2000 m, but below 2000 m, mafic eclogites are rare. Selected elements (Zr, Nb, Cr, Fe, Si, Mg, Al & Ti) in rutile from 39 eclogite cores from 100 to 2774 m, and major elements of minerals from representative eclogites were analysed by electron microprobe. Zirconium and Nb concentrations of rutile cluster ～100–400 and 200–700 ppm respectively. However, Zr and Nb contents in rutile from strongly retrograded eclogites show larger variations than those of fresh or less retrograded eclogites, implying that somehow fluid infiltration affected rutile chemistry during retrograde metamorphism. Zr contents in rutile inclusions in garnet and omphacite are slightly lower than those of the matrix rutile, suggesting that the rutile inclusions formed before or close to the peak temperature. The P–T conditions of the CCSD‐MH eclogites were estimated by both Fe–Mg exchange and Zr‐in‐rutile thermometers, as well as by the Grt–Cpx–Phn–Ky geothermobarometer. The maximum temperature range of 700–811 °C calculated at 40 kbar using the Zr‐in‐rutile thermometer is comparable with temperature estimates by the Fe–Mg exchange thermometer. The temperature estimates of eclogites in a ～3000 m thick section define a continuous gradient, and do not show a distinct temperature gap, suggesting that the rocks from 100 to 3000 m depth might belong to a single, large‐scale UHP slab. These data combined with P–T calculations for CCSD‐MH peridotites yield a low geotherm (～5 °C km^?1) for the Triassic subduction zone between the Sino‐Korean and Yangtze cratons; it lies ～30–35 mW m^?2 conductive model geotherm.     

Tale of the Kulet eclogite from the Kokchetav Massive,Kazakhstan: Initial tectonic setting and transition from amphibolite to eclogite

The Kulet eclogite in the Kokchetav Massif, northern Kazakhstan, is identified as recording a prograde transformation from the amphibolite facies through transitional coronal eclogite to fully recrystallized eclogite (normal eclogite). In addition to minor bodies of normal eclogite with an assemblage of Grt + Omp + Qz + Rt ± Ph and fine‐grained granoblastic texture (type A), most are pale greyish green bodies consisting of both coronal and normal eclogites (type B). The coronal eclogite is characterized by coarse‐grained amphibole and zoisite of amphibolite facies, and the growth of garnet corona along phase boundaries between amphibole and other minerals as well as the presence of eclogitic domains. The Kulet eclogites experienced a four‐stage metamorphic evolution: (I) pre‐eclogite stage, (II) transition from amphibolite to eclogite, (III) a peak eclogite stage with prograde transformation from coronal eclogite to UHP eclogite and (IV) retrograde metamorphism. Previous studies made no mention of the presence of amphibole or zoisite in either the pre‐eclogite stage or coronal eclogite, and so did not identify the four‐stage evolution recognized here. P–T estimates using thermobarometry and Xprp and Xgrs isopleths of eclogitic garnet yield a clockwise P–T path and peak conditions of 27–33 kbar and 610–720 °C, and 27–35 kbar and 560–720 °C, respectively. P–T pseudosection calculations indicate that the coexistence of coronal and normal eclogites in a single body is chiefly due to different bulk compositions of eclogite. All eclogites have tholeiitic composition, and show flat or slightly LREE‐enriched patterns [(La/Lu)_N = 1.1–9.6] and negative Ba, Sr and Sc and positive Th, U and Ti anomalies. However, normal eclogite has higher TiO₂ (1.35–2.65 wt%) and FeO (12.11–16.72 wt%) and REE contents than those of coronal eclogite (TiO₂ < 0.9 wt% and FeO < 12.11 wt%) with one exception. Most Kulet eclogites plot in the MORB and IAB fields in the 2Nb–Zr/4–Y and TiO₂–FeO/MgO diagrams, although displacement from the MORB–OIB array indicates some degree of crustal involvement. All available data suggest that the protoliths of the Kulet eclogites were formed at a passive continent marginal basin setting. A schematic model involving subduction to 180–200 km at 537–527 Ma, followed by slab breakoff at 526–507 Ma, exhumation and recrystallization at crustal depths is applied to explain the four‐stage evolution of the Kulet eclogite.     

新书介绍

根据发现于辽宁省西部朝阳地区下白垩统九佛堂组的离龙类一具有头骨的不完整骨架，建立Simoedosauridae科中的一新属新种：朝阳辽西龙：Liaoxisaurus chaoyangensis gen．et sp．nov．。朝阳辽西龙的下颌缝合部短，小于下颌长度的2O ，牙齿齿槽近似正方形，区别于任何已知的进步的离龙类。它吻部相对较短，占头骨总长的49．8 。     

安徽庐枞中生代富钾火山岩成因的地球化学制约

庐枞中生代火山岩产于下扬子断裂坳陷带的继承式火山盆地中，主要为一套以粗面玄武岩－玄武粗安岩－安粗岩－粗面岩为主体的偏碱质中基性岩石组合。化学成分上具有富碱、富钾、富轻稀土及大离子亲石元素（如Rb、Th、Pb)和贫高场强元素（如Nb、Ti)等特点。在郯庐断裂中南段及其邻近地区的中生代火山岩中，庐枞盆地火山岩的特征最接近钾玄岩系火山岩。这套火山岩具有较高的ISr值（0.70570-0.70653)及偏低的εNd(t)值（－5.01～-9.96)。火山岩产出地质背景的全面分析及元素－同位素的综合示踪，排除了岩浆上升过程中存在强烈的地壳物质的混染，富钾火山岩的岩浆源区应为受俯冲板片析出流体交代作用所形成的富集地幔（EMI），岩石主要起源于富集型地幔的部分熔融。     

广州城市快速公交干道网络设计

结合广州市天河路的案例分析,借助交通标准化和规模效益原理,利用地理信息系统的空间分析手段,尝试重新设计运量大、速度快、时效强的快速城市公共交通干线网络,提出建设广州城市一路一线快速公交网络模式的构想。认为一路一线的城市公共交通网络,既利于公交车辆的统一调配,提高道路使用效率,也便于按需发车,缩短等车时间,使整个城市公共交通的运营从真正意义上做到方便快捷。     

Provenance of Cored Sediments from Active Margin off Southwestern Taiwan Deduced from Geochemical Constraints

The cored sediments sampled by R/V Marion Dufrense in the active margin off southwestern Taiwan on the east side of the Manila Trench are mostly muds consisting mainly of quartz, feldspar, illite, chlorite ＋ kaolinite with a trace amount of montmorillonite. The cored sediments have higher Fe, Ti, Cr, Cs, Li, Ni, and V but lower Ca, Na, Mn, Hf, Nb, Sr, Ta, U and Zr contents when compared with the upper continental crust（UCC, Taylor and McLennan, 1985）. The Eu/Eu＊ ratios of the sediments averaging 0.69 indicate that the recycling effect on the Eu anomaly may be minor and the contribution of mafic source rock was unimportant, which can also be depicted in the La-Th-Sc plot（Cullers, 1994） showing a ＂mixed origin＂ close to the felsic end member. The chemistry of the cored sediment can be explained by a mixing model designed by Ho and Chen（1996） with four end members i.e., greywacke, shale, quartzite and limestone, which are widely distributed in the Cenozoic formations of southern Taiwan with greywacke as the dominant contributor followed by shale.     

祁连山冻土区天然气水合物DK一2钻孔微生物群落

对青海省祁连山永久冻土区天然气水合物DK一2钻孔的11件样品进行分析,通过微生物群落分析来探寻水合物层样品与非水合物层样品的差别。在11件样品中均发现了细菌16SrDNA,未检测到海洋天然气水合物地区常见的古菌16SrDNA、mc以（I,Ⅱ）、pmoA、mmoX和mxaF。分析得到的细菌16SrDNA分属5个门,包括变形杆菌门、放线菌门、拟杆菌门、厚壁菌门和异常球菌一栖热菌门,随着样品深度的增加,细菌多样性有降低的趋势。对非水合物层样品DK2—19和水合物层样品DK2—25进行细菌系统发育树分析,发现这2个样品群落结构相差较大。水合物层样品与非水合物层样品细菌群落对比后发现,水合物层样品中叫一变形杆菌的比例低于非水合物层样品中1一变形杆菌的比例,而Arthrobacter属多发现于非水合物层的样品中。