Experimental Study Of Phase Relations In The Ca-Ongonite From Ary-Bulak Massive (Transbaykal Region, Russia) at 700–800 °C

<p>An experimental study of three examples of the sub-volcanic body of Ary-Bulak ongonite was carried out to determine the composition of the liquidus phases and the order of crystallization of minerals. Phase relations in the samples of porphyritic ongonites (1), porphyritic ongonites with a high content of Ca and F (2)  and aphyric rocks with a high content of Ca and F (3) were studied at temperatures of 700–800 °C, a pressure of 1 kbar in Ni-NiO and Mt– Hem buffer conditions.</p><p>Rock samples have specific petrochemical aspects. In this series of rocks from (1) to (3), the general tendency is directed towards a decrease in the content of alkalis and silicon and an increase in the content of F and Ca.</p><p>Liquidus is achieved for porphyritic and aphyric ongonites with a high content of Ca and F. The liquidus phases for them are fluorite, topaz and plagioclase. Crystallization of porphyry ongonites begins at a temperature below 700 ° C.</p><p>The phase relationship and composition of the liquidus phases are independent of oxygen fugacity.</p>

The Morphotectono-Volcanic of Menoreh-Gajah-Ijo Volcanic Rock In Western Side of Yogyakarta-Indonesia

Menoreh-Gajah-Ijo have a very distinctive shape, where there are form of circular structure of volcano that is still intact and the other has not been intact. These morphologies are the morphology of the remaining volcanoes formed by tectonics and certain volcanisms. This study was conducted through a series of interpretations of volcanic body distribution, constructing a Slope Map, constructing a Slope Direction Map, constructing an alignment interpretation on satellite imagery and field mapping work. The formation of Menoreh-Gajah-Ijo morphologies are strongly influenced by tectonics and volcanic processes. The process of tectonism that produces the strike-slip fault structures, the normal faults, and the uplift have formed the lineaments of the valleys and hills with various directions patterns. The Menoreh-Gajah-Ijo volcanisms that have occurred form the structure of volcanic remains. Distribution of Menoreh-Gajah-Ijo volcanic rocks form some semicircle structures because of the normal fault structure that has occurred.

INTERPRETASI STRUKTUR BAWAH PERMUKAAN BERDASARKAN ATRIBUT ANOMALI MAGNETIK PERAIRAN WETAR, NUSA TENGGARA TIMUR

Struktur geologi yang berkembang di Perairan Wetar berupa Proto-Thrust-Zone, Frontal-Thrust dan Sesar Mendatar. Kelurusan anomali magnetik dikontrol oleh kontras suseptibilitas magnetik dari fenomena geologi. Interpretasi fenomena geologi berdasarkan anomali magnetik memperlihatkan Sesar Naik Wetar yang cukup jelas di bagian selatan, dan berpindah tidak menerus ke bagian timur daerah penelitian akibat Sesar Mendatar. Fenomena geologi lainnya berdasarkan metode horisontal derivatif orde 1 dan analisis sinyal terlihat jelas batas keberadaan tubuh batuan vulkanik. yang teridentifikasi dalam penampang seismik lintasan 5 dan 9. Metode ini cukup baik dalam memetakan struktur bawah permukaan. Di perairan Wetar sebagian anomali magnet tidak bisa diinterpretasikan jika dikorelasikan dengan penampang seismik. Hal ini terkait dengan hipotesis keberadaan paleomagnetik dan kerak Banda bagian selatan yang merupakan lempeng samudera yang terperangkap. Kata Kunci : magnet, horisontal derivatif, anomali, perairan Wetar Geological structures that develop in the Wetar waters are Proto Thrus Zone, Frontal Thrust Zone and Strike Slip Fault. Magnetic lineament controlled by sussceptibility contrast of geological phenomena. Interpretation of geological phenomena based on magnetic anomaly clearly show the strike-slip fault trending in the south, and move discontinuously eastward of the study area due to Strike-Slip Fault. Other geological phenomena clearly identified by horizontal derivative and signal analysis method such as the boundary of volcanic body as seen on seismic section line 5 and 9. These method quite usefull to map subsurface structure. Some part of the magnetic anomaly in the Wetar Waters cannot be interpreted since they are correlated with seismic section. It may be due to the hypothesis of the present of paleomagnetic southern Banda basin assumed as the trapped oceanic crust. Keywords: magnetic, derivative horizontal, anomaly, Wetar waters

NOVÉ POZNATKY O NEOVULKANITU V POHOŘI U ODER (OKRES NOVÝ JIČÍN)

The dyke on the Pohoř hill represents the most southeastern occurrence of Cenozoic volcanic rock in the Bohemian Massif. It has been studied since the second half of the 19th century, when it was discovered during a construction of railroad. Since that time the dyke has been considered to be hidden and there was no actual data about the site. We have carried out a ground magnetic survey to revise the location and shape of the volcanic body. Several boulders of the volcanic rock have been sampled. According to new petrographical and geochemical analyses we have classifi ed the rock from Pohoř as an olivine melilitite.

Bismuth and bismuth–antimony sulphosalts from Neogene vein mineralisation, Baia Borşa area, Maramureş, Romania

Several complex Cu-Pb-Bi, Cu-Pb-Bi-Sb and Ag-Pb-Bi sulphosalt minerals have been identified in samples from hydrothermal vein mineralisation associated with the Toroiaga sub-volcanic body in the Baia Borşa area of Maramureş County, northwest Romania. This is the first chemically-documented report of Bi-sulphosalts in the Neogene metallogenic province around Baia Mare. The investigated samples contain abundant amounts of matildite solid solution within galena, the Cu-Pb/Bi sulphosalts aikinite, friedrichite, krupkaite, hammarite, lindströmite and gladite as well as nuffieldite and berryite. Within the Ag-Pb/Bi group, the majority of analysed grains can be regarded as members of the lillianite homologous series. Three distinct lillianite homologues were identified, which correspond to (i) phases along the lillianite-gustavite solid solution join (Pb3Bi2S6-AgPbBi3S6), (ii) phases within solid solution field of heyrovskyite, and (iii) compositions which best correspond to ‘schirmerite’, sensu Makovicky and Karup-Møller (1977b), but may represent disordered gustavite, vikingite or eskimoite. Some of the analysed lillianite homologues contain excess Cu, which may occupy interstitial sites. Furthermore, a large proportion of the lillianite homologues display significant substitution of Sb for Bi within the limits predicted by experimental investigations. Cosalite, also showing a range of compositions including Sb-rich varieties is recognised. Izoklakeite, Cu2Pb22(Sb,Bi)22S57, is an abundant phase throughout the analysed samples, its composition is in good agreement with previously published analyses, except for excess Cu and Fe beyond the limits previously reported. The description of several minerals from this new occurrence and compositional data on them, including the Sb-bearing varieties, provides valuable additional information on compositional limits in natural samples.