Showing papers in "Lithos in 1968"

TL;DR: In this article, it is considered that the medium to high pressure granulite terranes reflect chemical trends with increasing depth in the continental crust, these trends are the results of modifications of the original compositions by metamorphic (including melting) processes.

TL;DR: In this paper, the positional and thermal parameters of synthetic forms of hydrous beryl and emerald and of anhydrous Beryl, emerald, and an emerald were refined by least square and difference Fourier methods using 3D data recorded with a counter diffractometer.

TL;DR: Garnet peridotites from Ugelvik, kimberlite pipes, the Czech Massif and also possibly those from Bellinzona in Switzerland may all be representative of essentially unmodified upper mantle material.

TL;DR: In this paper, Petrographic and mineralogical data are given for representative rock-types and twenty-two new chemical analyses are presented for the Mt. Misery lavas and comparisons are made with other calcalkali provinces.

TL;DR: A 3,000m-tholeiitic basalts are exposed in the Faeroe Islands as mentioned in this paper. But their formation came to an end before central volcanoes or subvolcanic bodies could develop.

TL;DR: In this paper, the metastability of ZrO 2 has been investigated in a range of P-T conditions, including at subsolidus temperatures for the Q-Ab-Or systems involved, during the raising of the temperature to about 800°C; at 800°c and 1 kilobar during runs of 50 to 233 hours; and at 900°C and 1kilobar after about 22 hours.

TL;DR: Leucogranites occurring within or adjacent to large granodiorite batholiths in the Snowy Mts. N.S.W., Australia, have a major element composition similar to that of the widespread rhyolites and ignimbrites of the North Island, New Zealand as mentioned in this paper.

TL;DR: In many chondrites orthopyroxene has been formed from low-calcium clinopyroxenes by thermal metamorphism as discussed by the authors, which has been shown to have equilibration temperatures below 900°C.

TL;DR: In this paper, the composition of coexisting biotite, Ca-amphiboles, and iron oxides in a metamorphic iron formation in Northern Sweden, analysed by micro-probe technique, is correlated with the oxygen pressure as indicated by the presence of distinct iron oxide minerals.

TL;DR: In this paper, the average chemical compositions of the rocks, their garnets and clinopyroxenes, have been calculated for each group and are presented here in tables and graphs.

TL;DR: In this article, the effects of time as a variable in relation to frictional heat generation during deformation which involves slip along interfaces is evaluated for several models and it is concluded that while frictionally generated heat is not alone responsible for the temperatures of metamorphism, it may, along with other sources of heat, contribute significantly to the heat budget of dynamothermally metamorphosed rocks and is capable of being responsible for differences observed in metamorphic reactions, e.g., andalusite →sillimanite in relatively rapidly deformed volumes at relatively low pressures and

TL;DR: In this paper, anorthite content of plagioclase from 38 anorthosite bodies including both layered and massif types was analyzed and a continuum of variation between the two extreme types of anorthites was found.

TL;DR: On the Kohler & Raaz diagram for rock analyses all projection points of tektites and impact glasses, except for the impact glass from Ries, lie inside the field of sedimentogenic rocks.

TL;DR: The authors reviewed previous petrogenetic studies of the Norra Karr alkaline body and contributed a considerable amount of new data, including more detailed mapping of the boundaries, provision of several new whole rock analyses and two K−Ar age determinations.

TL;DR: The theory of spinodal precipitation was applied to exsolution in feldspar as discussed by the authors, and it was shown that the spinodality does not take place at any appreciable rate.

TL;DR: In this article, a cookeite is described as large rosettes crystallized in an open vug in the Muiane granite pegmatite in Zambezia, Mozambique.

TL;DR: In this article, it is shown that the optimal representation of a mineral chemical analysis in terms of n molecular end members, ǫ, requires that: a. xj≥0 for all j, where xj are the amounts of the Ǫ; b. the error, Δ¯ǫ−AE−1ǫ*, between the observed and computed chemical analysis be a minimum.

TL;DR: An electron microprobe has been used to establish that sulphate-bearing mineral lattices have S K x peak positions which are lower than that of pyrite and a considerable number of other metal sulphide minerals by 32±5×10 −4 ngstrom units.

TL;DR: This 18O-content was determined in calcite, dolomite, ankerite, and hematite of three types of carbonatite as discussed by the authors, with a temperature of formation ≈200°C.

TL;DR: In some plutonic and metamorphic rocks of Japan, there can be a surprisingly wide difference in the An-content of the coexisting plagioclases even within one thin section.

TL;DR: The chemistry of the clinopyroxenes from each of these rock types is distinctive as discussed by the authors, while the pyroxenes of corundum eclogites and grospydites are aluminium rich.

TL;DR: The Buchanan massif is a Precambrian pluton covering about 100 square miles in the central Texas area, midway between the towns of Llano and Burnet as discussed by the authors, and shows a roughly concentric zonation from finegrained rocks in the interior of the pluton to coarse-grained and porphyritic rocks near the margin.

TL;DR: The authors showed that the formation of large assimilation zones is controlled by the mechanism of dispersal of material, which can take place by diffusion, crystal sinking, or convection, and at Meme-Casseus dispersal was caused largely by convection.

TL;DR: Tombarthite as mentioned in this paper is a hydrohydroxysilicate of rare earths found in one of the Precambrian granite pegmatite dykes in the Iveland-Evje area, South Norway as mentioned in this paper.

TL;DR: Niobian wolframite is an intermediate between wolfaamite and an iron-manganese niobate of the type FeNbO 4, and single crystal X-ray photographs indicate systematic extinctions consistent with the monoclinic wolfamite space group P2/c as discussed by the authors.

TL;DR: The processes of magmatic differentiation can be subdivided roughly into those that operate 1) at the time of magma formation, 2) while a magma is in transit, 3) during the emplacement of a magnetite, and 4) when a body of magnetite is at rest.

TL;DR: In this article, it is shown that it is possible to generate a set of molecules which obey charge balance and certain structural constraints of the amphibole group and which define a composition space within which natural amphiboles lie.

TL;DR: In this paper, a gabbroic-dioritic magma was emplaced below the rigid upper crust and the base of the magma envelope became filled with mush of crystals and magma.

TL;DR: In this paper, it was shown that for granites formed at elevated temperatures (orthoclase bearing granites), the hydrothermal model is not directly applicable; remelting of older rocks is here considered to be of importance, probably in accordance with the anatectic model of Walton.