Origins of Vulcanello based on the re-examination of historical sources (Vulcano, Aeolian Islands)

The lava platform and the three pyroclastic cones of Vulcanello constitute the northernmost volcanic structure of the island of Vulcano (Aeolian Islands). The sandy isthmus connecting the platform to the main island was definitively formed in the first half of the 1500s; before then, Vulcano and Vulcanello were two close but separate islands. For a long time, the interpretation of the sources of the II-I century BC, had considered the islet as built up about 2200 years ago. This belief, which proliferated among naturalists from the 17th century, is not confirmed in the ancient texts or even in the geographical documents of the time, which do not indicate the presence of Vulcanello as a new and stable island near Vulcano. The islet would only be mentioned at the dawn of the second millennium, and named in Arabic “Gabal’ al Burkān”, meaning Mount of Vulcano; shortly thereafter the toponym changed to the Latin “Insulam Vulcanelli” and then, towards the 15th century, finally to Vulcanello. Since the creation of a volcanic island certainly occurred in the Aeolian Islands in the classical era, but traces of it were quickly lost, the most plausible hypothesis is that it was formed in the area of the current Vulcanello, to be subsequently erased by the sea. The shallow, flat seabed, likely remaining as a result of sea abrasion, might have represented the morphological element on which the circular lava platform we know today was formed sometime between 950 and 1000 AD.

THE FUMAROLE «LEDOVAYA» OF ICHINSKY VOLCANO (KAMCHATKA) IN 2020

Ichinsky volcano is the largest volcanic structure of the Sredinny Range of Kamchatka. The manifestation of fumarole activity on the northern slope of the volcano is known since 1956. 64 years after the discovery of the Ledovaya fumarole, it was inspected with a quadrocopter. It was found that the fumarole is located at an altitude of 2725 m and is a large funnel up to 60 m in size, covered with snow in the middle part. In the upper part of the funnel there is a hole in the ice mass 9.8 m in diameter, with vapor-gas clouds rising up to 5–10 m above its edge.. The walls of the ice well are covered with a grayish-yellow fouling of sublimations. The authors believe that the probable temperature of the vapor-gas mixture of fumaroles at the outlet of the volcano rocks is significantly higher than 100° C.

Ore mineralogy of the Rodu-Frasin Au-Ag deposit, Metaliferi Mountains, Romania

<p>The Rodu-Frasin Neogene volcanic structure and associated Au-Ag mineralization are located in the north-eastern part of the Metaliferi Mountains, being part of the Baia de Aries - Rosia - Bucium metallogenetic district of the "Golden Quadrilateral".</p><p>The Rodu-Frasin region's geology consists mainly of Frasin dacite dyke and dome, polymictic volcanic and phreatomagmatic breccias and related volcano-sedimentary deposits, Badenian volcanic and sedimentary rocks, and Cretaceous sedimentary rocks.</p><p>Hydrothermal alteration in the region is pervasive and widespread throughout the volcanic structure and surrounding Cretaceous formation. Five main types of hydrothermal alterations have been described: potassic, propylitic, phyllic, silicic and carbonate. Argillic alteration is present only locally.</p><p>In the area of Rodu-Frasin deposit, the ore occurs in a structurally complex environment, influenced by faults and fractures oriented in two or more directions. Au-Ag-base metals mineralization is genetically associated with hydrothermal breccias and phreatomagmatic fractures.</p><p>Ore minerals consist of sulfides, gold, carbonates, adularia and quartz. They have been prevalently emplaced as veins, breccia bodies and disseminations in open fractures and breccias in the Rodu diatreme, and as stockworks, veins and disseminations in relationship to the Frasin dome structure.</p><p>The mineralized veins contain carbonates, quartz, pyrite, sphalerite, galena, chalcopyrite, tetrahedrite and gold. Magnetite and hematite, probably formed under mesothermal conditions, have been identified only as metasomatic substitutions of possible deep-breaking Cretaceous limestone clasts.</p><p>The deposition of the ore seemed to have a pulsating nature with the evolution taking place, possibly, in three stages to which the following mineral assemblages were described: 1. magnetite, hematite - pyrite, marcasite - quartz and pyrite - quartz ± base metal sulfides, in the first stage (mesothermal?); 2. arsenopyrite, Au - base metal sulfides - quartz - adularia, “chinga”, pyrite, Au - quartz - adularia and base metal sulfides - calcite, aragonite, dolomite, ankerite, ± rhodochrosite ± kutnahorite - quartz - adularia, in the second stage (epithermal low sulfidation) and 3. quartz - pyrite - marcasite - carbonates dominant rhodochrosite - Au and alabandite - rhodochrosite - quartz in the third stage (epithermal low sulfidation).</p><p>Gold is present in various proportions, either as small grains or as sub-microscopic occurrences and has been petrographically identified as electrum. The individual grains in native state have been observed as thin sheets on pyrite, sphalerite, rhodochrosite, calcite and quartz or as short wires and sheets in geodes. Local gold concentrations are common at the intersection of the locally-called “chairs” with “crosses” veins.</p><p><strong>Acknowledgments</strong></p><p>This work was supported by two Romanian Ministry of Research and Innovation grants, CCCDI – UEFISCDI, project number PN-III-P4-ID-PCCF-2016-4-0014 and PN-III-P1-1.2-PCCDI-2017-0346/29, within PNCDI III.</p>

LATE PALEOZOIC ALKALI-GRANITOID MAGMATISM OF SOUTHERN KAZAKHSTAN AND ITS ROLE IN THE FORMATION OF THE ORE-BEARING VOLCANIC STRUCTURES OF KENDYCTAS-CHU-ILI-BETPAK-DALA URANIUM ORE PROVINCE

Areas of distribution of alkaline granitoids in southernKazakhstanhave been identified, most of which are located within the Kendyktas-Chu-Ili-Betpakdalin uranium-bearing province, traditionally considered as Late Devonian-early Carboniferous. Arguments in favor of late Paleozoic age of alkaline rocks have been given. The proximity of the petrographic composition, petrochemical and geochemical features of the alkaline granites of the Chu-Ili-West-Balkhash area and late Paleozoic alkaline granites of the Zailiysky area has been established, confirming their age and continental rift origin. Similarity in the development of magmatism and hydrothermal mineralization of ore-bearing volcanic structures of the Chui area (Kurmanshitinskoe) and North-Western Chingiz (Ulkentuz and Dostar) has been revealed. In these structures, Devonian volcanic rocks are interspersed with subvolcanic bodies of comendites and later dikes of microgabbrodiorites and microdiorites. The hydrothermal mineralization of these structures took place in multiple stages. The early stage includes secondary quartzites, which developed in Devonian volcanogenic rocks. Comendite is associated with K-feldspated and albitized rocks, as well as with zones of rare-metal (Zr, Nb, Th, U and TR) Fe-Mg metasomatites that originated in the middle stage. In the later stage, after the introduction of microgabbrodiorite dikes, berezites with U-Mo mineralization formed. Comendites in the structures of the North-Western Chingiz break through the deposits D2-3 and D3-C1 and are considered to be the comagmatic alkaline granites of the neighboring late Paleozoic massifs (Tleumbet and Kuyrektykol). The noted similarity may also indicate that the Chui area comendites are likely to be dated to the late Paleozoic age. Examples have been given to the superposition of berezites and U-Mo mineralization on the late Paleozoic granosyenites, which are widespread in the Kurdai volcanic structure, as well as on the alkaline granites of Karasai volcanic structure. Their age may also be late Paleozoic. Additional research has been recommended for the final conclusions on the age of alkaline rocks and uranium mineralization.

The Brent Crater: An Alkaline Igneous Complex

The Brent Crater was discovered in 1951 from aerial imagery. The Crater was thoroughly investigated in the 1950s to early 1970s. The consensus throughout this period of exploration was that the crater was the result of a chondrite impact. This theory was disputed in 1971 in a paper by K.L. Currie who proposed that the crater was the result of alkaline volcanic activity within the Nipissing Alkaline Petrographic Province which resulted in geochemically and morphologically similar formations in the area of Lake Nipissing. Little research has been conducted to further verify or dispute this theory since. A 1977 national Uranium reconnaissance program followed up by a 1983 and 1984 field exploration and airborne geophysics program located a verified alkaline volcanic structure 15 km east of the crater known as the Allan Lake Carbonatite. The geophysical and geochemical data acquired from this work was processed to create aweighted probability raster of indicator elements of alkaline igneous materials. The Allan Lake anomaly demonstrates a more significant anomaly than the anomaly present at the Brent Crater. This anomaly is proposed to be the result of higher erosional rates in the crater. This hypothesis was tested by analyzing lake sediment concentrations of indicator elements in the nearby lakes. Given the world-renowned status of the Brent Crater as an example of a chondrite impact crater, it is important to either confirm Currie’s theory as a fact or disprove the theory to allow the structure to continue to act as an analogue without uncertainty.