The Batow pluton, an epizonal gabbroic body, Central Japan , was studied to delineate its geologic, petrographic and geochemical characteristics. Though the pluton is small, it exhibits a wide compositional range from melagabbro to granodiorite and varies from 42 .8 to 62.7 wt.% SiO2. The granitic rocks characterized by an abundance of amphibole (up to 39%) and a scarcity of biotite (less than 4%) were formed at a higher P H2O and lower temperature than early-crystallized gabbros. The close association of clinopyroxene-and biotite-rich gabbro, whose clinopyroxene and plagioclase often show reverse zoning in the Mg/(Mg+Fe*) ratio and An content, with amphibole-rich gabbro suggests that P H2O had increased rapidly during crystallization of the gabbroic melt. The intrusion of H2O-saturated granodioritic melt to the gabbroic melt may have caused the rapid increase of P H2O.
Fifty-seven samples of the Tuniff metavolcanic sequence from the Hastings region of the Grenville Province have been chemically analyzed. Ten major-element oxides and ten trace-element values for each sample were determined by standard X-ray fluorescence techniques. The sampled sections consist predominantly of mafic flows, subordinate intermediate flows, and minor felsic flows and pyroclastics. The sequence has been regionally metamorphosed to lower amphibolite facies. The geochemical data indicate that the metavolcanics represent a tholeiitic mafic-silicic bimodal sequence. Immobile-element discriminant diagrams indicate that the Turriff metabasalts are most similar to recent oceanic ridge basalts, whereas the metabasalts from other published studies of Grenville metavolcanics have an island-arc tholeiite affinity. However, because of the many chemical similarities between continental and oceanic ridge tholeiites, the bimodal nature of the sequence, and the field relationships, it is most likely that the eruption of the Turriff metavolcanics was associated with the rifting of continental crust, perhaps leading to the development of a marginal sea.Cinquante-sept Cchantillons de la sequence mCtavolcanique de Turriff de la region d'Hastings dans la province de Grenville ont kt6 analysCs chimiquement. Dix dkterminations d'oxydes d'C1Cments majeurs et d'C1Cments traces furent obtenues pour chaque Cchantillon selon les techniques habituelles de fluorescence des rayons-)<. Les coupes Ctudiees sont dominkes par des coulees mafiques, les coulees intermkdiaires sont moins abondantes, et il se trouve quelques coulCes felsiques ainsi que des roches pyroclastiques. La sCquence fut mCtamorphiste 5 1'Cchelle rkgionale dans les conditions caractCrisCes par le facies des amphibolites. Les resultats de I'analyse gkochimique rkvblent que les roches mCtavolcaniques reprksentent une sCquence bimodale mafique-silicique tholkiitique. Les diagrammes de discrimination des klements immobiles indiquent que les mCtabasaltes de Turriff sont trbs semblables aux basaltes rkcents des crktes ocCaniques, tandis que les metabasaltes dCcrits dans les Ctudes publikes sur les roches mCtavolcaniques du Grenville ont plutBt une affinitC avec les tholtiites d'arc insulaire. Cependant, si on tient compte des nombreuses similitudes chimiques entre les tholkiites continentales et celles des cr8tes ockaniques, de la nature bimodale de la sCquence et des relations observkes sur le terrain, il est plus probable que 1'Cruption des roches mCtavolcaniques de Turriff fut associte avec le stade de distention accompagne de creation de fossCs dans la croiite oceanique, pr6cCdant possiblement la formation d'une mer marginale.[Traduit par le journal]Can.
The linear relationship between the reciprocal of analyte‐line intensity, and the reciprocal of concentration has been applied to the determination of ten major and minor elements in silicate rocks and minerals. The analyses were carried out on fused specimens of 11 rock standards, with and without added La2O3, and with and without added NaNO3. The method requires no absorption matrix effect corrections, and is ideally suited to the analysis of geological materials with a wide range of chemical composition. It clearly has the advantage of simplicity and speed, and can be applied to the analysis of samples when suitable standards are not available. The results obtained in all cases are in excellent agreement with the literature. However, the discs with La2O3 added yield results with better precision and accuracy than do those without La2O3. Na2O is normally determined on separately prepared rock powder pellets, but can be satisfactorily analysed by this method, using the La2O3 added discs, together with all of the other major and minor elements. Na2O analyses are more readily obtained using discs without added NaNO3. We, therefore, recommend that the analysis of geological materials be carried out on fused glass discs with La2O3 added and without NaNO3.
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