Petrogenetic peculiarities of Fe-Ti oxide minerals in the processes of crystallization and evolution of late Cretaceous volcanic complexes of the Lesser Caucasus

Drawing from the determined differences between iron-titanium oxide minerals, we analyzed the conditions of crystallization and evolution of late-Cretaceous magmatic complexes of the Lesser Caucasus. It was found that the rocks of basalt-andesibasalt complex, which correspond to the early substage (upper Coniacian-lower Santonian) of late-Cretaceous volcanism in the Qazakh, Agjakand, Agdara depressions, have crystallized in the conditions of relatively highly- thermobaric crystallization of titanomagnetite, poorly differentiated and evolutionized according to the Fenner trend. In the second substage of volcanism, due to decrease in permeability of the Earth’s crust, the elevation of the remaining magma to the upper horizons was hindered. Therefore, within the Qazakh depression, shallow intermediate sites of crystallization developed where moderately titaniferous magnetite crystallized with the participation of oxidized fluids earlier than hornblende, pyroxene and plagioclase. Thus, the remaining magma evolutionized its composition through Bowen’s reaction series. In the Agjakand and Agdara depressions, change of previous expansion to compaction was the cause of hindering of partly fractioned portion of the magma. The latter thermally interacted with the above-embedded maghemite, hematite and in a number of cases magnetite. In the Khojavand depression, rocks of trachibasalt- trachiodolerite complex, which characterize the late substage of the Santonian volcanism, contain moderately titanium magnetites and maghemites. In the second substage of volcano-plutonism, rocks of tephrite-teshenite complex developed. There, accompanied by oxidized fluids, highly-clayey titanomagnetite crystallized before chrome-diopside and salite. However, the ulvospinel titanomagnetite in teshenites, having associated with barkevikite and kaersutite, crystallized at a relatively higher temperature. Within the Senonian volcanites of the Azykh depression, along with the moderately-titanium magnetite, chromic titanomagnetite and rarely chromite was determined. Similar mineralogical diversities are also characteristic for the Gochas depression.

A petrographic study of bauxite of Kenco area, Landak District, West Kalimantan Province

Lateritic bauxite are the products of intense weathering of rocks. It is largely controlled by bedrock type, time, climate (rainfall), and geomorphology. It is located in Kenco area, Landak district, West Kalimantan Province which the rest of the development of Cretaceous volcanism consisting of the island of Borneo Volcanic Formations Mensibau with unit members Granodiorite, quartz diorite and diorite, and the Formation of the Kingdom Volcanic Andesite-trachite units and Formations of alluvium and swamp sediment quarter. Bauxite deposits of Kenco area in Landak are investigated to determine the characteristics of rocks using petrographic analysis. Petrographic analysis aims to determine mineral content and type of source rock based on Travis classification (1955). The results of 15 thin sections showed that aluminum-bearing minerals consisted of orthoclase, plagioclase, and biotite which are the type of source rock are granodiorite, granodiorite porphyry, gabbro porphyry, and basalt porphyry based on Travis classification (1955).

Trilogy Of Southeast Sundaland Terranes: Re-Uniting Drifted Terranes of Southeast Sundaland Using Common Marker ff The Late Cretaceous Volcanics to Volcanic-Clastics of The Meratus Mountains, South Sulawesi, And Sumba - Implications For Petroleum Opportunities

Amalgamation and dispersion of terranes characterized the growth and slivering of Southeast Sundaland into the present configuration of central Indonesia. Amalgamation of the Paternoster-West Sulawesi terrane which docked, in mid-Cretaceous time, onto the Southwest Borneo terrane, thus closed the Meso-Tethys Ocean at the Meratus suture. This made Sundaland expand its area to the east and southeast. In the Late Cretaceous time, the Ceno-Tethys oceanic plate subducted beneath Southeast Sundaland, giving rise to coeval volcanism in the Meratus Mountains and the surrounding areas. Dispersion of some terranes in Southeast Sundaland occurred in the Paleogene through successive rifting and the opening of the Makassar Straits and the Flores Sea, with an eastern drift of South Sulawesi and Sumba away from Southeast Kalimantan to their present positions. Prior to the dispersion, the Meratus Mountains, South Sulawesi, and Sumba (called here the Trilogy of Southeast Sundaland) were united or adjacent to each other and underwent similar Late Cretaceous volcanism. The Late Cretaceous Volcanics and/or Volcanic-Clastics are therefore the common marker of their union. Our field studies in 2018-2019 at Sumba, South Sulawesi, and the Meratus Mountains (South Kalimantan) in the program, called the “Trilogy of Southeast Sundaland Terranes,” sampled the Late Cretaceous volcanics/ volcanic-clastics in these areas to prove that they were once united. Petrographic, petrochemical, isotopic, and geochronological data of the rock formations, based on the recent and previous analyses, show that these rocks, in the three terranes, are co-genetic spatially and temporally thus indicating their previous unity. The paired Paleogene dispersions of South Sulawesi from South Kalimantan, and successively Sumba from South Sulawesi, had resulted in rifted structures in the present Makassar Straits, the Flores Sea, and offshore Sumba. The rifted structures contain source rocks, reservoirs, seals, and structural-stratigraphic traps. Oil has been discovered therein, so further exploration is required since these objectives have not been sufficiently explored in the past and are thus still interesting.

Petrogenesis of the Upper Cretaceous volcanism in the Kefken region, Western Pontides, NW Turkey

<p>The Upper Cretaceous volcanic and volcaniclastic rocks crop out along the Black Sea coastline in Turkey. They are part of a magmatic arc that formed as a result of northward subduction of the Tethys ocean beneath the southern margin of Laurasia. The lower part of the Upper Cretaceous volcanism in the Kefken region, 100 km northeast of Istanbul, is represented by basaltic andesites, andesites, agglomerates and tuffs, which have yielded Late Cretaceous (Campanian, ca. 83 Ma) U-Pb zircon ages. The volcanic and volcanoclastic rocks are stratigraphically overlain by shallow to deep marine limestones, which range in age from Late Campanian to Early Eocene.  Geochemically, basaltic andesites and andesites display negative anomalies in Nb, Ta and Ti, enrichment in large ion lithophile elements (LILE) relative to high field strength elements (HFSE). Light rare earth elements (LREE) show slightly enrichment relative to heavy rare earth elements (La<sub>cn</sub>/Yb<sub>cn</sub> =2.51-3.63) and there are slight negative Eu anomalies (Eu/Eu* = 0.71-0.95) in basaltic andesite and andesite samples. The geochemical data indicate that Campanian volcanic rocks were derived from the partial melting of the mantle wedge induced by hydrous fluids released by dehydration of the subducted oceanic slab.</p><p>There is also a horizon of volcanic rocks, about 230 m thick, within the Late Campanian-Early Eocene limestone sequence.  This volcanic horizon, which consists of pillow basalts, porphyritic basalts,  andesites and dacites, is of Maastrichtian age based on paleontological data from the intra-pillow sediments and U-Pb zircon ages from the andesites and dacites (72-68 Ma).  The Maastrichtian andesites and dacites are geochemically distinct from the Campanian volcanic rocks. They show distinct adakite-like geochemical signatures with high ratios of Sr/Y (>85.5), high La<sub>cn</sub>/Yb<sub>cn </sub>(16.4-23.7) ratios, low content of Y (7.4-8.6 ppm) and low content of heavy rare-earth elements (HREE). The adakitic rocks most probably formed as a result of partial melting of the subducting oceanic slab under garnet and amphibole stable conditions.</p><p>The Upper Cretaceous arc sequence in the Kefken region shows a change from typical subduction-related magmas to adakitic ones, accompanied by decrease in the volcanism.</p><p> </p><p> </p>

Bosphorus Volcano; Signs of an Ancient Volcano on an Ancient City

<p>In many ancient and active volcanic provinces dyke systems represent radial and concentric patterns. In İstanbul, NW Turkey, late Cretaceous dykes, which are emplaced in pre-Cretaceous basement rocks consisting of sedimentary rocks of Palaeozoic and Triassic ages, have both patterns. In the region, late Cretaceous volcanism is represented by three elements, (1) The Çavuşbaşı granitoid, (2) volcano-sedimentary units and (3) dykes.</p><p>Age of the Çavuşbaşı granitoid is given as 67.91±0.63 to 67.59±0.5 Ma. It is emplaced in shallow depth and has an indistinct contact aureole. Volcano sedimentary units were deposited in an intra-arc basin. Three types of dykes are reported in the region: lamprophyre, diabase and intermediate to felsic dykes (72.49±0.79 to 65.44±0.93 Ma). Different petrology and the crystallization depths of the crystals in the dykes and the Çavuşbaşı granitoid suggest two different magma chambers emplaced at two different depths, the Çavuşbaşı granitoid representing the shallower one.</p><p>Upper Cretaceous dykes are concentrated around the Çavuşbaşı granitoid and extend almost as far as 30 km away from the pluton. The intrusion of the plutonic body of the Çavuşbaşı granitoid caused a dome structure in the basement rocks. The formation of this dome structure may have controlled the stress field and the orientation of the dyke system. Similar patterns are observed in the British Tertiary igneous province, Galapagos volcanoes, Boa Vista (Cape Verde), Summer Coon volcano, Spanish Peak Mountain and Dike Mountain (Colorado), Vesuvio, Etna and Stromboli (Italy).</p><p>We suggest that Upper Cretaceous volcanic edifice in the İstanbul region is related to an arc volcano similar to the andesitic volcanoes in the Sumatra Island; we name it the Bosphorus Volcano.  </p>

Detrital Zircon Provenance and Lithofacies Associations of Montmorillonitic Sands in the Maastrichtian Ripley Formation: Implications for Mississippi Embayment Paleodrainage Patterns and Paleogeography

We provide new detrital zircon evidence to support a Maastrichtian age for the establishment of the present-day Mississippi River drainage system. Fieldwork conducted in Pontotoc County, Mississippi, targeted two sites containing montmorillonitic sand in the Maastrichtian Ripley Formation. U-Pb detrital zircon (DZ) ages from these sands (n = 649) ranged from Mesoarchean (~2870 Ma) to Pennsylvanian (~305 Ma) and contained ~91% Appalachian-derived grains, including Appalachian–Ouachita, Gondwanan Terranes, and Grenville source terranes. Other minor source regions include the Mid-Continent Granite–Rhyolite Province, Yavapai–Mazatzal, Trans-Hudson/Penokean, and Superior. This indicates that sediment sourced from the Appalachian Foreland Basin (with very minor input from a northern or northwestern source) was being routed through the Mississippi Embayment (MSE) in the Maastrichtian. We recognize six lithofacies in the field areas interpreted as barrier island to shelf environments. Statistically significant differences between DZ populations and clay mineralogy from both sites indicate that two distinct fluvial systems emptied into a shared back-barrier setting, which experienced volcanic ash input. The stratigraphic positions of the montmorillonitic sands suggest that these deposits represent some of the youngest Late Cretaceous volcanism in the MSE.