某些不同成因类型磷灰石矿物学特征

本文通过对某些磷灰石的电子探针成分分析,X射线粉晶衍射及红外光谱特征的综合测试,发现这些磷灰石的晶体化学特征具有一定差异,因而有可能作为标型特征。其中与基性岩浆有关的磷灰石含OH~-较高,而CO_2较少;热液型的含氯较高,这可能是其α、c值较大的原因;沉积型的则以含明显的结构CO_2和高c/α值为特征。在各种地质作用中,CO_2均有可能进入磷灰石结构。根据红外光谱对比,推测2000cm~(-1)附近的吸收是磷灰石的固有吸收,它可能为PO_4的v_2吸收的倍频,也可能由与F、OH~-离子有关的振动引起。     

流动注射分析在电分析化学中的应用

本文拟就流动注射分析在电分析化学中的应用和进展作一概略的回顾和讨论     

Eruptive history and petrology of Mount Drum volcano,Wrangell Mountains,Alaska

Mount Drum is one of the youngest volcanoes in the subduction-related Wrangell volcanic field (80×200 km) of southcentral Alaska. It lies at the northwest end of a series of large, andesite-dominated shield volcanoes that show a northwesterly progression of age from 26 Ma near the Alaska-Yukon border to about 0.2 Ma at Mount Drum. The volcano was constructed between 750 and 250 ka during at least two cycles of cone building and ring-dome emplacement and was partially destroyed by violent explosive activity probably after 250 ka. Cone lavas range from basaltic andesite to dacite in composition; ring-domes are dacite to rhyolite. The last constructional activity occurred in the vicinity of Snider Peak, on the south flank of the volcano, where extensive dacite flows and a dacite dome erupted at about 250 ka. The climactic explosive eruption, that destroyed the top and a part of the south flank of the volcano, produced more than 7 km³ of proximal hot and cold avalanche deposits and distal mudflows. The Mount Drum rocks have medium-K, calc-alkaline affinities and are generally plagioclase phyric. Silica contents range from 55.8 to 74.0 wt%, with a compositional gap between 66.8 and 72.8 wt%. All the rocks are enriched in alkali elements and depleted in Ta relative to the LREE, typical of volcanic arc rocks, but have higher MgO contents at a given SiO₂, than typical orogenic medium-K andesites. Strontium-isotope ratios vary from 0.70292 to 0.70353. The compositional range of Mount Drum lavas is best explained by a combination of diverse parental magmas, magma mixing, and fractionation. The small, but significant, range in ⁸⁷Sr/⁸⁶Sr ratios in the basaltic andesites and the wide range of incompatible-element ratios exhibited by the basaltic andesites and andesites suggests the presence of compositionally diverse parent magmas. The lavas show abundant petrographic evidence of magma mixing, such as bimodal phenocryst size, resorbed phenocrysts, reaction rims, and disequilibrium mineral assemblages. In addition, some dacites and andesites contain Mg and Ni-rich olivines and/or have high MgO, Cr, Ni, Co, and Sc contents that are not in equilibrium with the host rock and indicate mixing between basalt or cumulate material and more evolved magmas. Incompatible element variations suggest that fractionation is responsible for some of the compositional range between basaltic andesite and dacite, but the rhyolites have K, Ba, Th, and Rb contents that are too low for the magmas to be generated by fractionation of the intermediate rocks. Limited Sr-isotope data support the possibility that the rhyolites may be partial melts of underlying volcanic rocks. Received March 13, 1993/Accepted September 10, 1993     

Radical variability determined from LIMS and SAMS satellite data

Using satellite data, the variability of a large number of stratospheric trace constituents can be estimated. These constituents need not themselves be measured by the satellite; their concentrations can be derived using photochemical steady-state relationships. The global coverage provided by the satellite over a long time period means that, for example, monthly zonal mean profiles can be derived. This has been done for H, OH, HO₂, H₂O₂, Cl, ClO, HCl, HOCl, ClONO₂, NO and O. The standard deviation of these quantities is a measure of their variability. We argue that comparing theoretical variability estimates with measurements is a better test of a photochemical theory than simply the comparison of single modelled and observed profiles.     

Fourier transform infrared kinetic studies of the reaction of HONO with HNO3, NO3 and N2O5 at 295 K

The kinetics of the reaction of nitrous acid (HONO) with nitric acid (HNO₃), nitrate radicals (NO₃) and dinitrogen pentoxide (N₂O₅) have been studied using Fourier transform infrared spectroscopy. Experiments were performed at 700 torr total pressure using synthetic air or argon as diluents. From the observed decay of HONO in the presence of HNO₃ a rate constant of k<7×10^-19 cm³ molecule^-1 s^-1 was derived for the reaction of HONO with HNO₃. From the observed decay of HONO in the presence of mixtures of N₂O₅ and NO₂ we have also derived upper limits for the rate constants of the reactions of HONO with NO₃ and N₂O₅ of 2×10^-15 and 7×10^-19 cm³ molecule^-1 s^-1, respectively. These results are discussed with respect to previous studies and to the atmospheric chemistry of HONO.     

What controls partial melting in migmatites?

Abstract The layers of six stromatic migmatites from Northern, Western, and Central Europe display small but systematic chemical and mineralogical differences. At least five of these migmatites do not show any signs of largescale metamorphic differentiation, metasomatism, or segregation of melts. It is concluded, therefore, that the compositional layering observed in most of the investigated migmatites is due to compositional differences inherited from the parent rocks. Almost isochemical partial melting seems to be the most probable process transforming layered paragneisses, metavolcanics, or schists into migmatites.
The formation of neosomes is believed to be caused by higher amounts of partial melts formed due to higher amounts of water moving into these layers. The neosomes have less biotite and more K-feldspar, if K-feldspar is present at all, than the adjacent mesosomes. These differences are small but systematic and seem to control the access of different amounts of water to the various rock portions. Petrographical observations, chemical data, and theoretical considerations indicate a close relationship between rock composition, rock deformation, transport of water, partial melting, and formation of layered migmatites.     

中国东部新生代玄武岩中低压单斜辉石的矿物化学及岩石学意义

本文搜集了中国东部11个省区新生代玄武岩中低压单斜辉石(Cpx)—斑晶、微晶Cpx的电子探针分析结果96个,通过大量的计算与投影,研究了Cpx的矿物化学特征,包括Cpx的种属划分及其成分特点,不同种属的Cpx成分变化及Cpx中SiO_2与其它氧化物的相关方程;也分析了Cpx矿物化学的岩石学意义,包括玄武岩的碱度顺序及系列划分,斑晶与微晶Cpx的成分差异及演化方向,Cpx结晶的温、压方程及斑晶形成的条件,玄武岩产出的板块构造环境等等。     

苏州A-型花岗岩性质的研究

本文从岩体地质构造、岩石结构和岩化性质,来论述苏州A-型花岗岩的非造山、无水和偏碱性特征。同时通过各种参数测定得知:本岩系中的钾长石和斜长石均为低结构态高有序度的。石英为β形。云母多为羟铁云母。副矿物有铌铁矿、磁铁矿、钛铁矿和碳硅石等四十多种。过渡性元素的Nb、Ta,Zr、REE、Y、Sn、Th、Ga和Zn丰度比其它类型花岗岩高出10倍到100倍,F的含量高得出奇,而Al、Ca、Mg则偏低。Ga/Al比值高。氧同位素值低,δ~(18)0(全岩)=7.53％。REE中Eu亏损严重。成岩时t=810℃,p=2     

Analysis of spatial water quality and stream networks in the southern Cotswolds during and after the drought of 1976

A study of water chemistry changes and stream network changes during and immediately after the 1976 drought is made in an area to the north and east of Bristol. In particular, contrasts are made between the Cotswold Limestone dip slope and the Severn Clay Vale. Immediately following the end of the drought a solute flushing effect was observed on the clay streams, whilst network extension on limestone streams incorporated new source areas and maintained higher solute concentrations throughout the post-drought period investigated.