Monazite-Xenotime-Garnet Equilibrium in Metapelites and a New Monazite-Garnet Thermometer

Prograde suites of pelitic rocks were examined with electronmicroprobe and laser ablation inductively coupled plasma massspectrometry to determine the systematics of element partitioningbetween coexisting monazite, xenotime, and garnet. Monazitegrains that grew in equilibrium with xenotime are enriched inY and Dy compared with monazite that grew in xenotime-absentassemblages. Y and heavy rare earth element contents of monazitecoexisting with xenotime increase with rising temperature. Monazite–xenotimeY–Gd and Y–Dy partitioning is systematic withina metamorphic grade, and increases slightly with increasingmetamorphic grade, suggesting that monazite–xenotime pairsapproached partitioning equilibrium. Garnet and monazite inboth xenotime-bearing and xenotime-absent assemblages show astrong ( R² = 0·94) systematic relationship between inversetemperature and ln(K_Eq) for the net-transfer equilibrium YAG+ OH-Ap + (25/4)Qtz = (5/4)Grs + (5/4)An + 3YPO₄-Mnz + 1/2H₂O,suggesting that garnet and monazite crystallized in compositionalequilibrium. The following temperature–K_Eq relationshipfor the equilibrium above has been derived:      

Adakite-like Lavas from Antisana Volcano (Ecuador): Evidence for Slab Melt Metasomatism Beneath Andean Northern Volcanic Zone

Extensive sampling of the Antisana volcano in Ecuador (NorthernVolcanic Zone of the Andes) has revealed the presence of adakite-likerocks throughout the edifice, i.e. rocks with geochemical characteristicsclose, but not identical, to those of slab melts. Two main volcanicgroups have been distinguished, characterized by two distinctevolutionary trends. The AND group, mostly composed of andesites,shows the clearest adakitic characteristics such as high La/Yband Sr/Y ratios and low heavy rare earth element (HREE) contents.The CAK group, composed of high-K andesites and dacites, displaysless pronounced adakitic-like characteristics. Although themore basic rocks of each group are difficult to distinguishon many geochemical diagrams, a geochemical study shows thatthe evolution of the AND and CAK groups is dominated by differentpetrogenetic processes. The isotopic characteristics of theCAK rocks suggest that evolution of this group is dominatedby a limited assimilation–fractional crystallization processwithin the granitic continental basement of the cordillera.In the AND group, the abundances of incompatible elements, suchas Nb or HREE, suggest that the series was produced by a partialmelting process in a mantle rich in garnet, amphibole and/orclinopyroxene. Such a mantle source has been demonstrated (experimentallyand by exhumed mantle xenoliths) to be produced in subductionzones where slab melts react with and metasomatize the mantlewedge. In Ecuador, magmas erupted in the Western Cordillera(trenchward relative to Antisana volcano) are true adakites,suggesting that slab melts can be responsible for the metasomatismof the mantle wedge beneath the NVZ in Ecuador. If mantle convectioncan drag down this modified mantle beneath Antisana volcano,destabilization of metasomatic amphibole at appropriate pressuresin this modified garnetiferous mantle can adequately explainthe formation and the geochemical features of Antisana lavas. KEY WORDS: subduction; adakite; metasomatism; Ecuador; AFC; Sr and Nd isotopes     

Geochemical and Isotopic (O, Nd, Pb and Sr) Constraints on A-type Granite Petrogenesis Based on the Topsails Igneous Suite, Newfoundland Appalachians

The voluminous, bimodal, Silurian Topsails igneous suite consistsmainly of ‘A-type’ peralkaline to slightly peraluminous,hypersohnis to subsolvus granites with subordinate syenite,onzonite and diabase, plus consanguineous basalts and highsilicarhyolites. _Nd(T) values from the suite range from –1.5to +5.4; most granitoid components exhibit positive _Nd(T) values(+1.1 to +3.9). Granitoid initial ⁸⁷Sr/⁸⁶Sr and most ¹⁸ O valuesare in the range expected for rocks derived from mantle-likeprotoliths (0.701–0.706 and +6 to +80/). Restricted ²⁰⁷Pb/²⁰⁴Pbvariation is accompanied by significant dispersion of ²⁰⁶Pb/²⁰⁴Pband ²⁰⁸Pb/²⁰⁴Pb. Superficially, petrogenesis by either direct(via fractionation from basalt) or indirect (via melting ofjuvenile crust) derivation from mantle sources appears plausible.Remelting of the granulitic protolith of Ordovician are-typegranitoids can be ruled out, because these rocks exhibit negative_Nd(T) and a large range in ²⁰⁷Pb/²⁰⁴Pb. Geochemical and isotopicrelationships are most compatible with remelting of hybridizedlithospheric mantle generated during arc-continent collision.A genetic link is suggested among collision-related delaminationor slab break-off events and emplacement of ‘post-erogenic’granite suites. A-type granites may recycle previously subductedcontinental material, and help explain the mass balance notedfor modern arcs. However, they need not represent net, new,crustal growth. KEY WORDS: A-type granites; juvenile crust; isotopes; Newfoundland ^*Telephone: (613) 995-4972. Fax: (613) 995-7997. e-mail: jwhalen{at}gsc.emr.ca     

Minor-element and Revised Major-element Contents of Some Mediterranean Pantellerites and Comendites

Optical emission spectrographic analysis of three pantelleritesfrom Pantelleria and two comendites from Sardinia show highconcentrations of B, Be, Ga, La, Mo, Nb, Sn, Y, Yb, and Zt andlow contents of Ba, Co, Cr, Ni, Sr, and V. Minor-element trendsof these specimens are very similar to those of pantelleritesfrom southern Nevada and New Zealand and other peralkaline silicicrocks from various localities. Fluorine contents of the Pantellerianspecimens range from 0.19 to 0.32 per cent by weight resultingin abnormally high Cl to F ratios. New analyses for MgO, Na₂O,and K₂O are almost identical with the values obtained by Zies.Revised major-element compositions and calculated glass-phasecompositions for the three Pantellerian specimens are given.     

首次在中国发现的矿物

本文主要内容是根据作者近期发表在英文杂志《岩石与矿物》上的同名文章译成的,它追述了在中国发现的新矿物种（类）的基本历史。列出了在中华人民共和国发现的99种矿物的名字及其发现地点和文献出处。本文修正了英语文献中的大量错误,从语言学角度介绍了矿物学在英文和中文交流之间存在的困难。作者为中文稿增加了一些新内容,更新了几处发现地的资料,还增加了一个新矿物：碲锌（铁）石（Zineospiroffite）,它发表在英文稿付印之后。本文按化学组成和年代顺序对中国发现的新矿物进行了分析。所有列出的新矿物都是经过IMA-CNMMN批准的或者是“祖先级”（“grandfathered”）的矿物,只有一个是没有被批准的矿物。新矿物是按英文字母的顺序排列的。     

THEORETICAL ANALYSIS OF AN IMPERVIOUS,HEATED-CYLINDER ‘GROUNDWATER VELOCIMETER’

An isothermally heated, impervious cylinder, which is placed normal to the path of flowing groundwater, is theoretically evaluated for its potential to serve as a kind of ‘groundwater velocimeter’. The essential task is to determine whether the variation in heat output along the cylinder perimeter is sufficiently large to permit measurement for typical groundwater velocities. Using finite elements, the governing equations of advective thermal transport in saturated porous media are solved to obtain the variation in heat output along the circumference of the heated cylinder. An annular region of different hydraulic conductivity is assumed to separate the cylinder from the surrounding formation. The creation of such a region during placement of a cylinder is inevitable. A parametric study led to the following conclusions: (1) A smaller cylinder radius is preferable since the time to achieve a particular degree of asymmetry in heat output is then greatly reduced. (2) An annular region of lower hydraulic conductivity, relative to formation, reduces output asymmetry by no more than 25%, but if hydraulic conductivity is increased, output asymmetry can increase several times. (3) For annular regions having a higher hydraulic conductivity than the surrounding formation, annular thickness is not important. (4) The least groundwater speed which may be accurately measured by such a device will depend heavily upon instrumentation but is tentatively placed at about 5⋅0×10⁻⁵ cm/s. Theoretical results are approximately confirmed by preliminary experiments with a prototype device which has been constructed so as to directly measure the expected variation in thermal output. Partial construction details are provided.     

Can an atmospherically forced ocean model accurately simulate sea surface temperature during ENSO events?

The performance of an atmospherically forced ocean general circulation model (OGCM) in simulating daily and monthly sea surface temperature (SST) is examined during the historical El Niño Southern Oscillation (ENSO) events during the time period 1993–2003. For this purpose, we use the HYbrid Coordinate Ocean Model (HYCOM) configured for the North Pacific north of 20°S at a resolution of ≈9 km. There is no assimilation of (or relaxation to) SST data and no date-specific assimilation of any data type. The ability of the model in simulating temporal variations of SST anomalies is discussed by comparing model results with two satellite-based SST products. The HYCOM simulation gives a basin-averaged monthly mean bias of 0.3 °C and rms difference of 0.6 °C over the North Pacific Ocean during 1993–2003. While the model is able to simulate SST anomalies with mean biases  <0.5 °C  in comparison to observations during most of the ENSO events, limitations in the accuracy of atmospheric forcing (specifically, net short-wave radiation) have some influence on the accuracy of simulations. This is specifically demonstrated during the 1998 transition period from El Niño to La Niña, when a record large SST drop of  ≈7 °C  occurred in the eastern equatorial Pacific Ocean.     

THE GEOGRAPHICAL DIMENSIONS OF AL‐QA'IDA RHETORIC

ABSTRACT. This article examines the geographical ideology of al‐Qa'ida. The central questions are to what extent al‐Qa'ida terrorism is motivated by a desire to control geographical space, and how the organization defines that space as place in its communiqués. The study also asks whether al‐Qa'ida's geographical rhetoric reveals the nature or locations of future attacks. Principal sources are statements and interviews by and with al‐Qa'ida leaders. al‐Qa'ida classifies distinctive geographical realms of legitimization, preparation, and action. Its geographical concerns and ambitions are hierarchical and based principally on perceptions of sacred space. The holy places of Mecca, Medina, and Jerusalem are the cornerstones of a greater Islamic holy land that al‐Qa'ida seeks to rid of non‐Islamic‐especially U.S. and “Zionist”‐elements and replace with a new caliphate. Terrorism directed principally against American civilians in the United States is one of the main tactics by which al‐Qa'ida says it hopes to achieve its goals in geographical space.     

Fundamental operations in computer-assisted map analysis

Abstract

Geographical information systems (GIS) provide capabilities for the mapping, management and analysis of cartographic information. Unlike most other disciplines, GIS technology was born from specialized applications. A comprehensive theory relating the various techniques used in these applications is only now emerging. By organizing the set of analytic methods into a mathematical structure, a generalized framework for cartographic modelling is developed. Within this framework, users logically order primitive operators on map variables in a manner analogous to traditional algebra and statistics. This paper describes the fundamental classes of operations used in computer-assisted map analysis. Several of the procedures are demonstrated using a fourth-generation computer language for personal computers.