Chemical Petrology of Grenville Schists near Fernleigh, Ontario     

HOUNSLOW  A. W.; MOORE  J. M.  JR 《Journal of Petrology》1967,8(1):1-28

A suite of mica schists from the staurolite zone was studiedin detail. Phase rule considerations and distribution relationsindicate that chemical equilibrium was attained within the samplevolume. Iron-magnesium ratios of the silicates vary greatly,and correlate with rock ferrous-ferric ratio, as does the oxidemineral mode. Rock oxidation state varies locally, and is probablydependent on the composition of the original sediment. Distribution coefficients for Fe, Mg, and Mn among garnet, biotote,and staurolite show no vaiation attributable to temperature.Partition of Fe and Mg between staurolite and biotite is regular,but non-ideal. The staurolite structure permits only limited(15–35 percent) substitution of Mg for Fe.  相似文献   

Contrasting morphological trends of islands in Central Philippines: Speculation on their origin     

Graciano P. Yumul JR    Carla B. Dimalanta  Rodolfo A. Tamayo JR    Jenny Anne L. Barretto 《Island Arc》2000,9(4):627-637

Abstract The Palawan microcontinental block collided with the Philippine Mobile Belt in the Central Philippine region resulting in the counterclockwise rotation of Mindoro– Marinduque and clockwise rotation of Panay. The collision also brought about the clockwise rotation of north-east Negros, Cebu, north-west Masbate and Bohol (collectively called the Western Visayan block), resulting into their present-day northeast–southwest trend. This suggests a far more dramatic role of the collision than was previously recognized. Furthermore, the south-east Sulu Sea sub-basin is inferred to have also undergone collision-related clockwise rotation which can account for the observed east-west trending magnetic lineations in the basin. Aside from explaining the contrasting morphological trends of the different islands in Central Philippines, the rotation can also explain, albeit in a different way, how the belts of sedimentary basins, ophiolites and arcs in Panay and Negros can extend to Northern Luzon. Published paleomagnetic data suggest that the collision-related rotation commenced during the early to middle Miocene and had ceased by the late Miocene.  相似文献   

腾格里沙漠区盐湖物质成分研究   总被引：8，自引：2，他引：6       下载免费PDF全文

肖应凯  B.D.Vocke JR  魏海珍 《盐湖研究》2000,8(3):21-26

腾格里沙漠面积广阔 ,区内分布着数十个盐湖 ,盐湖面积大的为十余平方千米 ,小的仅为 0 .0 18km2 。盐湖卤水主要为湖表卤水 ,其矿化度较高 ,大部分盐湖卤水含盐量已达饱和 ,因而进入了自析盐阶段。盐湖卤水化学成分以 Na+ 、K+ 、Cl-、SO4 2 -、HCO3 -、CO3 2 -为主 ,占卤水总含盐量的 99% ,卤水中还有 B2 O3 、L i、I、Br等微量元素。盐湖盐类沉积有碳酸盐类、硫酸盐类和氯化物型盐类、主要盐类矿物为芒硝、钾芒硝、天然碱、泡碱、碳钾钠矾、石盐等。盐湖粘土矿物组合以蒙脱石的普遍存在为特征 ,含有少量的伊利石和水云母。  相似文献   

甘露醇对石墨存在下Cs2BO2^＋离子热电离质谱法测定硼同位素的影响   总被引：3，自引：2，他引：1       下载免费PDF全文

肖应凯 JR  BDV 《盐湖研究》2000,8(3):14-20

对石墨涂样检测Ｃｓ２ＢＯ２＾＋离子条件下甘露醇对硼同位素测定的影响进行了研究,结果表明在甘露醇存在下＾１１Ｂ／＾１０Ｂ比值明显高于只有石墨存在时的比值。硼－甘露醇络合物的形成可能改变了Ｃｓ２Ｂ０２＾＋－石墨方法的电离和蒸发条件。  相似文献   

‘Locationally disadvantaged’: planning governmentalities and peri-urban agricultural futures     

Laura Wynne  Dana Cordell  Brent Jacobs 《The Australian geographer》2020,51(3):377-397

ABSTRACT

Peri-urban areas are the interface between urban and rural regions, with these regions traditionally acting as foodbowls for adjacent urban areas. This peri-urban agriculture provides a diverse suite of benefits to urban areas. Increasingly, however, peri-urban areas are being converted to residential uses, driven in part by higher land values secured for land converted for residential development. In Sydney, planning and development has tended to treat peri-urban areas as ‘suburbs in waiting’. Using a Foucauldian governmentality approach, this paper investigates the prevailing rationalities in metropolitan-level strategic planning documents—in particular A Plan for Growing Sydney and the Draft South West District Plan—and how these rationalities relate to peri-urban agriculture. Our analysis shows that the three overarching rationalities—the global city, the compact city and the sustainability agenda—frame the urbanisation of peri-urban agricultural lands as necessary and inevitable, and only integrate agriculture as part of the future of the city of Sydney when it can be rationalised within the ‘global city’ narrative. As a result, peri-urban areas are not considered to have unique planning needs, but are imagined as latent spaces that will enable Sydney to meet its housing and job targets through their future development.  相似文献   

新疆博格达造山带晚古生代构造-岩浆演化过程:火山岩组合及地球化学证据   总被引：9，自引：3，他引：6  

王金荣  李泰德  田黎萍  于漫  王怀涛  赵志雄  汤中立 《岩石学报》2010,26(4):1103-1115

最近,笔者在博格达山东段北部的西地-伊齐-小红柳峡一带的地质调查中发现,该区发育有大量晚石炭世柳树沟组双峰式火山岩及早二叠世卡拉岗组酸性火山岩建造,但双峰式火山岩性质及成因有别于其南侧七角井早石炭世双峰式火山岩。玄武岩富钠贫钾(K_2O=0.18%～0.45%,Na_2O=2.24%～3.63%),属拉斑系列;TiO_2=1.6%～1.7%,略高于MORB,较高的Al(Al_2O_3=16.2%～16.7%)、高Mg(MgO=8.12%～9.54%,Mg~#=61～64),以及低K_2O/TiO_2和K_2O/P_2O_5比值(分别为0.1～0.27、0.63～1.68),反映了在岩浆演化过程中分离结晶作用不明显;Rb/Sr比值0.01～0.02,Zr/Nb=21.6～39.7,Zr/Y=5.38～7.47,以及不相容元素Ba、Zr、Hf相对略富集、Nb-Ta和Th相对亏损,显示岩石具有板内玄武岩的特点;稀土元素球粒陨石标准化配分图上整体接近于平坦型,(La/Yb)_N=1.8～1.9,Eu无异常至轻微正异常(δEu=1.07～1.12),正ε_(Nd)(t)值(+5.63～+5.89),(~(143)Nd/~(144)Nd)_I=0.512927～0.512944,Th/Yb0.2,Ta/Yb=0.1,表明玄武岩浆源于亏损软流圈地幔,且在演化过程中不曾发生过斜长石的分离结晶作用,并暗示当时的大陆地壳可能由于拉张而变得较薄,玄武岩浆形成后快速上升至地表喷发。双峰式火山岩中的流纹岩Rb-Sr等时线年龄为296±2Ma(1σ),具高Si(SiO_2=76%～80%),富钾贫钠(K_2O=5.1%～5.7%,Na_2O=0.94%～2.03%);低Al(Al_2O_3=7.9%～10.4%);低Ti、Ca和P含量,属高钾钙碱性系列;微量元素Rb、Th、Zr、Hf、K相对富集,Ba、Sr、P、Ti、Nb、Ta为显著亏损;轻稀土元素适度富集且轻、重稀土分馏程度低,(La/Yb)_N=5.1～7.1,(La/Sm)_N=2、(Gd/Yb)_N=1.6～2.2,以及强烈的负Eu异常(δEu=0.17～0.2),(~(87)Sr/~(86)Sr)_I=0.7051～0.7052,δ~(18)O=11.6‰,指示岩石源于地壳物质的部分熔融,源区存在有斜长石残留,形成于大陆裂谷环境。早二叠世末流纹岩(Rb-sr等时线年龄为278±2Ma)具高Si(SiO_2=74%),富钾贫钠(K_2O/Na_2O2),低Al(Al_2O_3=11.0%)以及较低的Ti和P含量的特征,岩石为高钾钙碱性系列;微量元素PM标准化图解上表现为Rb、Ba、Th、U、K、La、Ce不相容元素相对富集,高场强元素Nb、Ta、P、Ti以及Sr为明显的负异常;轻稀土轻度富集,(La/Yb)_N=5～6,(La/Sm)_N=3,(Gd/Yb)_N=1.3～1.4,以及强烈的负Eu异常(δEu=0.31～0.39),(~(87)Sr/~(86)Sr)_I为0.7069,δ~(18)O=11.97‰,指示源于地壳物质部分熔融的产物,形成于伸展垮塌的构造环境。综合研究结果表明,博格达山前身裂谷岩浆作用始于早石炭世,结束于晚石炭世末期,早二叠世末进入后造山伸展的演化阶段。  相似文献   

云南瓦渣钨矿区老君山花岗岩体的SHRIMP锆石U-Pb定年、地球化学特征及成因探讨   总被引：13，自引：5，他引：8  

冯佳睿  毛景文  裴荣富  周振华  杨宗喜 《岩石学报》2010,26(3):845-857

云南省瓦渣钨矿区位于老君山花岗岩体的东北接触带,属于滇东南-桂西白垩纪钨锡多金属成矿区中的组成部分。该矿床与矿区西部大面积分布的老君山第一期中粗粒二云二长花岗岩在时间和成因上有着密切联系。本文通过SHRIMP锆石U-Pb测年、岩石主量元素、微量元素和稀土元素的系统研究,进而探讨该花岗岩的形成年龄和动力学背景、岩石物质来源以及形成温度和压力。研究表明,与瓦渣钨矿床有关的中粗粒二云二长花岗岩属于高钾钙碱性岩系,为强过铝质S型花岗岩。岩体形成时代为83.3±1.5Ma,属于晚白垩世,形成于岩石圈伸展环境,其源岩为富粘土的泥质来源,其形成温度为875～900℃,压力约为7×108Pa,相当于深度为26km。  相似文献   

WMO     

LLOYD W. SWIFT JR  WAYNE T. SWANK 《水文科学杂志》2013,58(3):245-246

ABSTRACT

Long term changes in streamflow following forest cutting are presented for three experimental basins at Coweeta Hydrologic Laboratory, North Carolina, USA. Previous analyses have shown that, following forest cutting, streamflow increases and then declines with the logarithm of time as the forest regrows. Recent data indicate that the streamflow decline following cutting is related to vegetation regrowth, but the relationship is not a consistent function of simple stand measurements. The mixed hardwood forest of one basin was clearcut twice in the past 40 years. During the second regrowth period, streamflow increases after the first year were about one-half the increases at the same points in time after the first treatment. Concurrent with the second cutting, two other basins were cut whose mid-elevations are 400 m higher. The increases for the upper basins were similar, even though basal area was reduced by only 65% on one. Both streamflow increases were less than for either cutting on the lower basin. Variability of flow increases for the three concurrent treatments is similar and appears partly related to precipitation.  相似文献   

Geographical information systems and planning in the USA: selected municipal adoption trends and educational concerns     

WILLIAM R. GORDON JR  NADER M. SOUBRA 《International journal of geographical information science》2013,27(4):267-278

Abstract

Practitioners and academics from many fields of study are currently facing numerous issues involving the diffusion of technologies from geographical information systems within their respective professions. This paper has two aims. The first is to report the partial results of a postal survey of selected municipal planning departments in the U.S.A. In measuring trends related to the adoption of computer and geographical information system technologies, the survey focuses on the availability of trained geographical information system and computer literate staff and on alternative means of training existing staff, as well as on the adequacy of collegiate education. The presentation of survey results is used to establish a framework for the principal discussion of this paper. The second part examines the relationship between planning and education in geographical information systems. Parallels within other disciplines and professions are derived. Curricula and training considerations within academic programmes and professional practice are suggested.  相似文献   

The effects of introduced water hyacinth on habitat structure,invertebrate assemblages,and fish diets     

Jason?D.?ToftEmail author  Charles?A.?Simenstad  Jeffery?R.?Cordell  Lenny?F.?Grimaldo 《Estuaries and Coasts》2003,26(3):746-758

The South American floating aquatic plant water hyacinth (Eichhornia crassipes) has a history of worldwide invasions, including a 1904 introduction into the Sacramento-San Joaquin Delta, California. The native pennywort (Hydrocotyle umbellata) occupies similar habitats in the Delta and is extensively used by resident invertebrates and fish. We sought to discover if an invader would be functionally equivalent to the native plant, by asking whether the encroadhing hyacinth modified the invertebrate assemblage structure and fish-invertebrate food web relative to pennywort. We sampled epiphytic, epibenthic, and benthic invertebrates, and plant canopy insects in patches of hyacinth and pennywort, and analyzed fish diets at three sites in the Delta during 1998. We also measured habitat structure (leaf density, root biomass, and surface area). In 1999, following control and absence of hyacinth, we again measured epiphytic invertebrates in pennywort. We found differences between hyacinth and pennywort in structure, associated invertebrates, and fish diets. Most measurements inferred functional non-equivalency between hyacinth and pennywort, although some functional equivalency and natural variation existed. Leaf and insect densities were significantly higher in pennywort and there were also significant differences in insect assemblage compositions. Hyacinth roots in the water column had significantly more surface area. Densities of epibenthic and benthic aquatic invertebrates were typically greater in pennywort and taxonomic compositions of aquatic invertebrate assemblages showed significant differences. Amphipods and isopods living epiphytically in the root masses were particularly abundant, including several newly discovered introduced species: the amphipodCrangonyx floridanus and the isopodsCaecidotea racovitai andAsellus hilgendorfii. The native amphipodHyalella azteca was more abundant in pennywort and heavily preyed upon by fish, while the non-indigenousC. floridanus was more abundant in hyacinth and not prevalent in fish diets. The introduction of hyacinth to the Delta has caused significant ecological alterations in the surrounding community, due to hyacinth being functionally different from native patches of pennywort.  相似文献