Augitite, potassic limburgite, pyroxene trachybasalts and trachyte-andesite are found in the Pliocene layers. Potassic basanite and limburgite are found in the Pleistocene layers. Holocene layers contain augitite, leucite basanite, potassic hawaiite and leucite tephrite. Horgo/Khorgo is constructed from phonolitic tephrite and its lavas range alkali basalt-basanite.
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Cerro Seguro, a large hill underlain by Cieneguilla Basanite and Ortiz quartz monzonite The younger intrusions in the belt are increasingly alkaline in composition, and include the 25-26 Ma Cieneguilla basanite. This is a small-volume extrusive unit exposed around the village of La Cienega that may represent the earliest stages of opening of the Rio Grande rift. The basanite is characterized by olivine phenocrysts in a matrix of clinopyroxene, magnetite, and nepheline, with a total silica content of 42.40-44.10 wt % and a high magnesium oxide content (11.50-13.50 wt %). This places the basanite among the most primitive magmas of the central Rio Grande rift.
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In the north west, there was so much lava that valleys filled and overflowed. A plain resulted with up to 750 meters thickness, and maximum extent south of Wynyard and Burnie. In the late Eocene and early Oligocene lakes were formed near Waratah. Older alkaline basalt in the north west is from , at Table Cape basanite from and at Stanley basanite is dated to and .
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Other Quaternary volcanic centres in the region are Nelson Island and the Kusilvak Mountains. Olivine basalt is the principal volcanic rock but basanite and nephelinite are also found.
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Macdonald has principally erupted basalt. This basalt contains phenocrysts of clinopyroxene, olivine and especially plagioclase. Additional rocks are basanite, mugearite, picrite and tephrite. The overall composition is alkaline and nephelinic.
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The Meidob volcanic field has erupted basalt, basanite, hawaiite as well as benmoreite, mugearite, phonolite and trachyte, forming an alkaline suite of volcanic rocks. Various types of xenoliths are present in the eruption products, while phenocrysts include aegirine, amphibole, anorthoclase, augite, biotite, ulvospinel-magnetite, nepheline olivine, augitic-diopsidic pyroxene and sanidine. The total volume of erupted rocks is about , which was erupted at rates of . Basalt and basanite lava flows make up most of the erupted material.
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The composition of the current eruptive products of Erebus are anorthoclase-porphyritic tephritic phonolite and phonolite, which are the bulk of exposed lava flow on the volcano. The oldest eruptive products consist of relatively undifferentiated and nonviscous basanite lavas that form the low broad platform shield of Erebus. Slightly younger basanite and phonotephrite lavas crop out on Fang Ridge—an eroded remnant of an early Erebus volcano—and at other isolated locations on the flanks of Erebus. Erebus is the world's only presently erupting phonolite volcano.
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Príncipe is situated in shallower water, rising 3000 meters from the seafloor to 948 meters above sea level at Pico do Príncipe. The island is built on a base of palagonite breccia, which includes pieces of basalt that was part of a tholeiitic magma series which developed deep below water. Basalt covers the north of the island, while tephrite and phonolite are common in the south. Geologists have sub-divided the basalts between older series of basanite and hawaiite, which are intruded by many, younger nephelinite and basanite basalt dikes.
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Prindle Volcano, the northernmost volcano of the Northern Cordilleran Volcanic Province and one of the most isolated volcanoes in Alaska, was formed on the Yukon-Tanana upland during the Pleistocene epoch. It is a small cinder cone made of basanite with a deep breached volcanic crater at its summit. Extending from Prindle's breached volcanic crater is a long basanite lava flow that flowed southeast of the cone then flowed southwest into a river valley. The Cassiar Mountains and Tanzilla Plateau in northern British Columbia are dominated by tuyas of the broad Tuya Volcanic Field.
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The field has erupted basalt, basanite, rhyolite and trachyte. They contain amphibole, clinopyroxene, magnetite and olivine phenocrysts. Patterns in trace element composition and isotope ratios imply that the magmas either developed from variable starting material or from metasomatized mantle.
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Pico do Fogo consists of basanite, tephrite, phonotephrite, clinopyroxene, amphibole, magnetite, olivine, melilite and leucite. The main magma chamber is about 16-24 km deep, into the ocean crust and 10-12 km in the bottom of the crust.
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Rocks include basalt and trachybasalt. Olivine basalt, basanite and tholeiite have been found as well, with smaller amounts of trachyandesite. Tephras from different eruptions do not display significant differences in composition. Ultramafic xenoliths have been found in the rocks.
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Magma ascent has been controlled by northwest-trending faults. Volcanism in the wider territory was related to the subduction of the Farallon plate until 29 mya. Later tectonic changes caused a start of more alkaline volcanism. The volcanoes have erupted basanite.
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Trachyte is the most common rock on Mount Takahe, phonolite being less common. Basanite, hawaiite, and mugearite are uncommon, but the occurrence of benmoreite and pantellerite has been reported, and some rocks have been classified as andesites. Hawaiite occurs exclusively in the older outcrops, basanite only in parasitic vents and mugearite only on the lower sector of the volcano. Despite this, most of the volcano is believed to consist of mafic rocks with only about 10–15% of felsic rocks, as the upper visible portion of the volcano could be resting on a much larger buried base.
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The field has erupted alkali basalt, basanite and hawaiite. Phenocrysts include clinopyroxene, olivine and plagioclase. There are also xenoliths including dunite, gabbro, granite, and notably ultramafic to mafic xenoliths. The rock composition has not changed much during the history of the Cima volcanoes.
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The isolated San Martin Tuxtla volcano is a shield volcano which rises above the Gulf of Mexico. It has had eruptions in historical times. It occurs in the Tuxtla volcanic field in Veracruz, Mexico. Lavas from San Martin vary between basanite and alkali basalt.
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The high altitude limestones are associated with the Vindobonian Volcanic Complex, which includes trachyte, diabase and dolerite intrusions, along with pyroclastic flow sediments. Basalt is the most common rock type on Madeira and geologists have found a variety of different types including alkali-basalt, basanite and hawaiite.
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Dredging has yielded basaltic rocks which define alkali basalt and basanite suites. The flows contain phenocrysts of clinopyroxene, iddingsite, olivine, plagioclase and sometimes spinel. Lava flows are covered by manganese crusts less than thick. They often display traces of alteration and formation of glasses such as palagonite.
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Basanite, basalt, benmoreite, hawaiite, phonolite, trachyandesite, trachyte and tristanite have been recovered from The Pleiades. These volcanic rocks define two separate sodium and potassium-rich magma suites and may originate from separate levels of the same magma chamberKyle 1982, p.749,751 or through fractional crystallization.Stump 1986, p.
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The basement consists of metamorphic and plutonic rocks of Precambrian age, which are part of the Tuareg shield. Outcrops of granite are found in some places. These were first buried by tholeiitic basalts between 35 and 30 million years ago. The field has mostly erupted basalt and basanite.
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An origin by fractionation from basanite through nepheline hawaiite to nepheline benmoreite has been demonstrated for a volcanic suite in the McMurdo Volcanic Group of late Cenozoic age in McMurdo Sound area of Antarctica. Nepheline benmoreite magmas derived from mantle sources, containing lherzolite xenoliths, display similarities to some plutonic nepheline syenites.
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Basanite is the dominant rock of outcrops, with phonolite less common and picrobasalt and tephrite rare. Outcrops of older rocks include mugearite, rhyolite and trachyte. Textures range from porphyritic to seriate. Various phenocrysts are found within the volcanic rocks, including aegirine, augite, clinopyroxene, alkali feldspar, kaersutite, nepheline, olivine, plagioclase, quartz and sanidine.
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The Kookooligit Mountains are a volcanic mountain range on north-central St. Lawrence Island in the U.S. state of Alaska. They consist of a long and wide shield volcano capped with over 100 smaller volcanic cones.Global Volcanism Program: Kookooligit Mountains The volcanic cones are composed primarily of alkali olivine basalts, olivine tholeiite, and basanite.
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Active faults occur throughout the region. Atakor has erupted basalts, phonolite and trachyte, the latter two form lava domes. The basalts are characterized by alkali basalts and basanite and form about 80% of all volcanic rocks in Atakor, with less important occurrences of benmoreite, hawaiite, mugearite and rhyolite. Phenocrysts in some volcanic rocks include amphibole, clinopyroxene, olivine and zircon.
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Tephrites have been found at Qal'eh Hasan Ali, as well as basanite and an augite-phlogopite cumulate. The tephrites contain analcime, anorthoclase, clinopyroxene, hauyne, magnetite, olivine, phlogopite and pyroxene dominated by augite and lesser aegirine. Xenoliths have also been found at the Great Crater vent, including probably magmatic calcite. Apatite is present at the Great Crater as well.
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A close-up of the youngest lava flow The Lunar Crater vents have erupted alkali basalts; trachyte occurs at two lava domes and basalts, basanite, tephrite and trachybasalt have been reported as well. In general, the volcanic rocks define an ocean island basalt suite that originated in the asthenosphere. The rocks contain phenocrysts. inclusions and nodules.
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The summit is located in the eastern part of the volcanic massif of the Cantal. Formed of basanite, it is a remnant of a basaltic lake formed of solidified lava and is the site of the most recent volcanic activity in the range. It was formed 2.9 million years ago, above an accumulation of several layers of pyroclastic trachyandesite.
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Its altitude extends from 197 m to 210 m. It is close to a military zone (escuadrilla logística de Cuatro Puertas). The site is among a zone of dark-coloured pyroclasts of varying sizes, dating from the Pleistocene era, made of basanite and nephelinite. It is on a steep slope (sloping angle > 45° in some places).
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Te Uku limeworks opened in the 1930s, just north of Te Uku Landing. Over about 15 years it crushed several thousand tons for agricultural use and driveways, initially with a traction engine and later with electric power. Okete quarry opened beside Okete Falls in the 1940s. The rock is Basanite, erupted between 2.69 and 1.8 million years ago.
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Sumaco is a symmetrical, isolated stratovolcano, that is set off from the main Ecuador volcanic axis. Its rocks are very distinct from those from most Andean volcanoes because of its lack of andesitic composition, in favour of basanite and phonolitic rock. Sumaco is heavily forested and contains a small cone in its broad summit crater. An historical eruption occurred around 1895 (± 30 years).
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North Arch volcanic field is an underwater volcanic field north of Oahu, Hawaii. It covers an area of about and consists of large expanses of alkali basalt, basanite and nephelinite that form extensive lava flows and volcanic cones. Some lava flows are longer than . This volcanic field appears to be somehow related to the Hawaii hotspot, although the exact mechanisms are debated.
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Other estimates indicate Holocene activity, supported by stratigraphic relationships of Cerro Ventana and Cerro Contreras lava flows with nearby river sediments. The Holocene Tagua ash (<2712–2360 BP) may originate from the Crater Basalt volcanic field but there are geographical and petrological problems with this theory. The shield volcanoes have formed basalt as eruption products. Crater Basalt basalts include basanite and trachybasalts.
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Once the alkali olivine basalt flows cooled, they formed well-developed columnar joints. Feldspar-phyric, highly vesiculated hawaiites and benmoreites were later erupted from several vents on the summit of Itcha Mountain. In the northwestern and northeastern parts of the shield volcano, basanite lava flows were erupted and are volumetrically subordinate. These represent the youngest known lavas of the Itcha Range.
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The Hans Heiling Rocks on the Ohře west of Karlovy Vary : Variscan granite of the Bohemian Massif just south of the southern fault line of the graben in the Falkenau Basin. Mravenčák (left) and Černý vrch, two tephrite-basanite kuppen on the northern edge of the Doupov Mountains opposite Klášterec nad Ohří The Bořeň near Bílina, an isolated tephrite-basanite erosion stump on the transition from the Bohemian Central Uplands into the North Bohemian Basin View from Milešovka into the Bohemian Central Uplands over the North Bohemian Basin, inter alia with the coal-fired power station of Ledvice and the brown coal open-cast mine of Bilina. In the background is the southern edge of the Ore Mountains and the town of Litvínov. The Eger Graben (, ), much less commonly called the Ohre or Ohře Graben, is a geographical unit in the Czech Republic.
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Volcanic rocks from Daiichi-Kashima include basanite, benmoreite and mugearite. There is a distinction between the eastern and western sectors of the volcano, with the western one consisting mainly of mugearite. Phenocrysts identified in sampled rocks include aegirine-augite, alkali feldspar, amphibole, chromium spinel, clinopyroxene, magnetite, olivine and plagioclase. Dredging has found limestones on Daiichi-Kashima which have been subdivided into an upper and a lower formation.
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Trachyandesite and trachyte are the most common rocks on Mount Melbourne, with basalt being less common and mostly occurring around its base. The rocks define a mildly alkaline suite rich in potassium unlike the rocks elsewhere in the volcanic field. The rest of the volcanic field also features alkali basalts, basanite and mugearite. Phenocrysts include aegirine, amphibole, anorthoclase, augite, clinopyroxene, hedenbergite, ilmenite, magnetite, olivine, plagioclase and sanidine.
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MIT Guyot has erupted basaltic rocks, with rock composition changing over time from alkali basalts over basanite to hawaiite. Phenocryst phases include clinopyroxene, olivine and plagioclase, and apatite, augite and pyroxene are additional components. Isotope ratios resemble these of the northern Wake seamounts and of the Marquesas hotspot. Alteration of basalts has given rise to clay, chlorite, goethite, hematite, hydromica, kaolinite and especially smectite but also zeolite.
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Hot basaltic magma rises along these fractures to create passive lava eruptions. The compositions of lavas in the Northern Cordilleran Volcanic Province are mantle-derived alkali olivine basalt, lesser hawaiite and basanite, which form the large shield volcanoes and small cinder cones throughout the volcanic province. Many of them contain inclusions of lherzolite. The large central volcanoes of the volcanic province consist largely of trachyte, pantellerite, and comendite lavas.
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Cerro de los Chenques is a monogenetic volcano in the Chubut Province, Argentina, which is considered to be of Holocene age. The volcano developed on a basement formed by Mesoproterozoic and Neoproterozoic rocks and more recent volcanic and granitic formations. The volcano is source of lava flows and pyroclastics. Cerro de los Chenques has erupted rocks ranging from alkali basalt to basanite, which contain phenocrysts ranging from clinopyroxene, olivine and plagioclase.
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Each volcano type produced by the Anahim hotspot has its own unique life cycle of growth and erosion. Volcanic cones have their origins from tephra accumulating around vents during Strombolian eruptions. They are composed of trachyte, trachyandesite, basalt, phonolite, basanite and to a lesser extent phonotephrite. In contrast, lava domes are formed mainly by viscous trachytic magma that erupts effusively onto the surface and then piles up thick around vents.
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Vlinder Guyot has erupted alkali basalt, basanite and hawaiite containing hornblende and plagioclase, oceanite, tholeiite and trachybasalt, while Oma Vlinder has erupted hawaiite. Isotope data show some affinity to rocks recovered at Pitcairn and Rarotonga. Other materials encountered include pelagic chalks, ferromanganese crusts up to thick, hyaloclastite, limestone of foraminiferal and reefal origin, mud, phosphorite, turbidites, volcaniclastic rocks as well as lithified clays, gravelstones, sandstone, siltstone and tuffites.
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Lava flows of more viscous phonotephrite and trachyte erupted after the basanite. The upper slopes of Mount Erebus are dominated by steeply dipping (about 30°) tephritic phonolite lava flows with large-scale flow levees. A conspicuous break in slope around 3,200 m ASL calls attention to a summit plateau representing a caldera. The summit caldera was created by an explosive VEI-6 eruption that occurred 18,000 ± 7,000 years ago.
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Lava domes, fallout and pyroclastic flow deposits are also common. Among the vents is the Malha crater, which presently contains a small lake. The volcanic field has erupted rocks ranging from basanite to trachyte and rises from a tectonic uplift known as the Darfur dome. Volcanic activity in Meidob began 6.8 million years ago and continued into the Holocene, with the most recent eruptions dated to 4,900 ± 520 years ago.
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Emi Koussi has erupted phonolite, trachyandesite and trachyte, as well as mafic rocks like basanite and tephrite. The erupted rocks define two alkaline suites. Phenocryst chemistry and content varies between the various rocks; among the minerals are alkali feldspar, amphibole, biotite, clinopyroxene, olivine, oxides and plagioclase. Alkali feldspar, apatite, clinopyroxene, olivine, magnetite, mica, nepheline, oxides, plagioclase, quartz, sodalite, titanite and zircon also form the groundmass of microliths in erupted rocks.
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These are overlain by thick mafic alkaline lava flows and at least 30 small cinder cones. Hawaiite is the dominant rock type, but alkali olivine basalt and spinel lherzolite-bearing basanite is also present. They merge laterally with lavas of the much older Chilcotin Group, which surrounds the Anahim Volcanic Belt. However, the exact nature of the relationship between the Anahim Volcanic Belt and the Chilcotin Group is unknown.
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Eruption products consist chiefly of alkaline basalt and basanite. Volcanism in the Austral Volcanic Zone is less vigorous than in the Southern Volcanic Zone. Recorded eruptions are rare due to the area being unexplored well into the 19th century; the cloudy weather of its western coast might also have prevented sightings of eruptions. The Austral Volcanic Zone hosts both glaciated stratovolcanoes as well as subglacial volcanoes under the Southern Patagonian Ice Field.
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Theralite (from Greek "to pursue") is, in petrology, the name given to calcic foidal gabbro, a plutonic hylocrystalline rock consisting of augite, olivine, calcic plagioclase (labradorite), and nepheline, along with accessories including biotite, magnetite, ilmenite and analcime. Theralite is the intrusive equivalent of nepheline basanite, a foidal basalt with essential calic plagioclase and essential olivine. Tephrite is foidal basalt with essential calic plagioclase but without essential olivine. It is essentially the volcanic equivalent of essexite.
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The Big Pine volcanic field has erupted basaltic rocks spanning a range of composition from alkali basalt to basanite, as well as one unit of silicic rocks. Phenocrysts include olivine, plagioclase and clinopyroxene. The erupted rocks also contain xenoliths such as lherzolite, pyroxenite and wehrlite. The magmas erupted in the Big Pine volcanic field were generated by melting of lithospheric mantle that had been modified by subduction processes 1.8 billion years ago.
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Sedimentary deposition and some volcanic activity took place during the Mesozoic, particularly in the lowlands of the St. Lawrence Platform. Central Montreal is underlain by 119 to 117 million year old plutonic basanite, lamprophyre and camptonite while to the immediate southeast amphibole gabbro and peralkaline rocks formed from 141 to 123 million years ago. Cretaceous intrusive rocks formed hills housed in the sedimentary rocks of the St. Lawrence Lowlands Platform, notably Mount St. Bruno.
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Subvolcanic intrusions in the Northern Cordilleran Volcanic Province are exposed in areas of high relief. This includes volcanic plugs found at the Mount Edziza volcanic complex, Level Mountain, Hoodoo Mountain and in the Atlin and Maitland areas. Volcanic plugs in the Atlin and Maitland areas consist of olivine nephelinite and basanite magmas. Minor plugs made of gabbroic and granitic magma are associated with volcanic stratigraphy at the Mount Edziza volcanic complex and Level Mountain.
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Kimberlitic rocks from the Buffalo Head Hills kimberlite field. Display by Alberta Geological Survey.The volcanic rocks of the BHH and BM fields are classified as kimberlites. The ML rocks are not considered to be archetypal kimberilte and have been variously classified as alkaline ultramafic rocks, hybrid alkaline ultramafic rocks, alkali olivine basalt and basanite; they are difficult to classify because of strong clay alteration that has obliterated most of their original mineralogy.
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In 1657, he was finally accepted as a member of the Accademia di San Luca. After 1658, he did decorative work for Cardinal Flavio Chigi; painitng flowers on mirrors and basanite columns. He also collaborated with other artists to paint flowers with figures at the Palazzo Chigi in Ariccia. These paintings represent the Four Seasons and each artist was assigned to assist with one of them: Filippo Lauri (Spring), Carlo Maratti (Summer), Giacinto Brandi (Fall) and Bernardino Mei (Winter).
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Bayuda has erupted basaltic rocks, with most collected rocks belonging to an alkali basalt suite although basanite, melabasanite, hawaiite and trachybasalt have been identified as well. Phenocrysts include clinopyroxene and olivine. Various xenoliths have been found, including garnet-containing clinopyroxenite, harzburgite, garnet hornblendite, amphibole-containing peridotite, olivine and spinel pyroxenite and websterite. In general the composition resembles that of other Sudanese-Egyptian volcanoes, about two different magma families have been identified which originate from disparate mantle domains.
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Eruptive activity in the Northern Cordilleran Volcanic Province throughout its 20 million year history has been mainly the production of alkaline lavas, including alkaline basalts. A range of alkaline rock types not commonly found in the Western Cordillera are regionally widespread in the Northern Cordilleran Volcanic Province. These include nephelinite, basanite and peralkaline phonolite, trachyte and comendite lavas. The trachyte and comendite lavas are understood to have been created by fractionation of mainly alkali basalt magma in crustal reservoirs.
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The Mountain Lake cluster consists of two diatremes or volcanic pipes in Northern Alberta, Canada. It was emplaced during a period of kimberlite volcanism in the Late Cretaceous epoch. Although they were originally described as kimberlite or kimberlitic, the Mountain Lake (ML) rocks were later reclassified as alkaline ultramafic volcanics, hybrid alkaline ultramafic rocks, basanite or alkali olivine basalt. Due to extensive clay alteration that obliterated much of their original mineralogy, the question of their proper classification remains unsettled.
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This volcanism manifests itself with 18 large and numerous smaller volcanoes, which occur in groups, rows or as solitary systems in Marie Byrd Land. The larger centres have produced phonolite, rhyolite, trachyte and rocks with intermediate compositions, and reach heights of over above sea level. The smaller centres are found at the foot of the larger centres, as parasitic vents on their slopes or along the coast. These vents have produced alkali basalt, basanite and hawaiite.
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The rocks of Montiferru are the remains of an extinct volcanic complex, covering an area of about , that was active 3.9 to 1.6 million years ago during the Pliocene and Pleistocene epochs of the Earth's geological history. The volcanic activity was at its most intense 3.6 million years ago. The volcano erupted a wide variety of lavas including basanite, hawaiite, phonolite, mugearite, benmoreite and trachyte, as well as small amounts of basaltic andesite and basaltic trachyandesite.
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Special "subsidence areas" are the Nördlinger Ries and the Steinheim crater, both originating through a meteorite impact event. The Cenozoic deposits in the Central European Blocks region consist of both siliciclastic rocks and limestones and both marine and continental sediments. The Cenozoic in Germany is also represented by volcanic rocks. In contrast to the mostly acidic (SiO2-rich) volcanic rocks of the transition level, the Cenozoic formations are mostly intermediate to very SiO2-poor (trachyte, basalt, phonolite, tephrite, nephelinite and basanite).
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The field has erupted basanite and phonolite with a total volume of about , additional volcanic rocks are basaltic andesite, hawaiite and tephrite. Basaltic rocks range from alkali basalt to tholeiite. Potassium- argon dating has yielded an age of about 12 to 1 million years ago for the field; activity commenced in the Eocene with the basaltic plateau and continued in the late Eocene and later with lava domes and individual volcanoes. Volcanic activity has been subdivided in several separate cycles.
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The Pali-Aike volcanic field is mainly made up of basalt and basanite, which form a sodium-rich alkaline suite; hawaiite is rare. The most important phenocrystic phase is olivine which also appears as xenocrysts; other minerals include clinopyroxene, diopside and plagioclase. The groundmass has a similar composition with the addition of augite, feldspar and magnetite and occasionally ilmenite and nepheline. Pali-Aike rocks typically contain ultramafic xenoliths containing augite, dunite, eclogite, garnet, harzburgite, lherzolite, peridotite, phlogopite, pyroxenite, spinel and wehrlites.
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Dake, H.C., Fleener, Frank L. and Wilson, Ben Hur, Quartz Family > Minerals: A Handbook for the Mineral Collector, pub. Whittlesey House, a > division of the McGraw Hill Book Company, Inc. 1938. Basanite (not to be confused with bassanite), Lydian stone, and radiolarite (a.k.a. lydite or flinty slate) are terms used to refer to several types of black, jasper-like rock (also including tuffs, cherts and siltstones) which are dense, fine-grained and flinty / cherty in texture and found in a number of localities.
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Pyroclastics and lava flows of phonolitic and trachytic composition form the "mesa" flows and are concentrated in the central part of the field. The more differentiated rocks are prevalent in the more recent rocks. Basanite is a product of mantle melts, which may involve a lithospheric component. Fractionation processes in deep magma chambers and assimilation of crustal materials have been used to explain the genesis of differentiated magmas from the basanitic precursor, with additional processes generating the basaltic and hawaiitic magmas.
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In contrast to most mountain ranges in British Columbia, the Itcha Range represents an inactive shield volcano. This highly dissected volcanic edifice consists of a variety of rock types, including basanite, hawaiite, trachyte, rhyolite, phonolite and alkali olivine basalt. They were deposited by different types of volcanic eruptions characterized by passive lava flows and explosivity. Two stages of eruptive activity have been identified at the volcano along with three sub-phases that are limited only to the first stage of development.
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This basanite statue of Agrippina the Younger as a priestess of the divine Claudius, 54–59 AD, was discovered on the Caelian Hill in 1885. Under Augustus the Caelian Hill was one of the 14 divisions of the town, called Caelimontium. The area between the Lateran and Porta Maggiore was included in the v Regio (Esquiliae), though physically it is part of the hill. On the higher point of the side facing the Colosseum, the Temple of Claudius was erected on a huge supporting platform.
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These in turn are overlain by the varied cyclic sequences of the Lower Limestone Formation. The igneous rocks are relatively resistant to erosion and form the main scarp and two summits. A quartz-dolerite sill of probable Permo-Carboniferous age, forming a part of the Midland Valley Sill Complex intrudes the early Carboniferous sedimentary rocks of the Lower Limestone Formation. The peaks of West Lomond and Green Hill are nepheline-basanite intrusions whilst East Lomond is a teschenite/olivine dolerite intrusion and vent agglomerate.
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Volcanic rocks dredged from Vesteris include basanite as the major component, phonotephrite and tephrite but also alkali basalt, mugearite and trachybasalt. Samples taken are porphyritic, rich in vesicles and contain phenocrysts of amphibole, clinopyroxene, kaersutite, olivine and plagioclase; these minerals also make up the groundmass of the rocks. These volcanic rocks define two separate geochemical suites, one formed by the basanites-tephrites and the other by the alkali basalts-mugearites. The formation of these two magma suites has been explained with fractional crystallization processes, mixing between different magmas and partial melting.
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The volcanic rocks are of variable though mainly silica-undersaturated character with basanite, nephelinite and phonolite among the lava types found. Geochemistry of the alkaline volcanic-subvolcanic rocks of the Fernando de Noronha Archiapelago, southern Atlantic Ocean The main island, from which the group gets its name, makes up 91% of the total area; the islands of Rata, Sela Gineta, Cabeluda and São José, together with the islets of Leão and Viúva make up the rest. The central upland of the main island is called the Quixaba.Carlos Secchin, Clóvis Barreira e Castro, Arquipélago de Fernando de Noronha, 2nd ed. 1991.
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Samples taken from the North Arch volcanic field are fine grained or glassy with varying quantities of vesicles and consist of alkali basalt, basanite and nephelinite, with variable chlorine, magnesium, potassium and sulfur contents. Olivine is the most important phenocryst, although clinopyroxene and spinel are also found. This diverse composition stems from variable melting from a common source rock with subsequent fractionation of olivine and garnet; the source rock appears to be ultimately a product of both mantle and mantle plume components. Hyaloclastite is also found; clay and palagonite found in the field may have formed from volcanic ash through e.g.
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Limestone up to 193 meters thick marks the Upper Jurassic in central Israel, followed by the basalt Tayasir volcanic rocks, the 120 meter Kurnub Group sandstone, limestone and clay, and 670 meters Nabi Sa'id, Ein el Esad, Hidra, Rama and Kefira formation marl, chalk, sandstone and limestone from the early Cretaceous. Basalt and basanite are both exposed from the Cretaceous in the north. Limestone, dolomite, chalk and marl formed during Turonian and Santonian times, chalk and chert during the Campanian. The Mishash Formation of the same age contains similar rocks, 86 meters thick, but also phosphorite.
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The hill contains a slender, chilled margin of fine-grained basalt with most of the mass of the intrusion being made up of picrite and dolerite. Volcanic rocks on the hill are predominantly mafic. Minerals, and as well as volcanic material, found on the hill are follows: analcime, apophyllite, basanite, basalt, trachyte, aragonite, barite, calcite, chabazite, chlorite, heulandite, ilmenite, laumontite, leucitite, limburgite, montmorillonite, natrolite, nephelinite, olivine, pectolite, pyrite, phillipsite, prehnite, quartz, rhyolite, siderite, trachybasalt, trachyandesite, tuff and high level intrusives; rare volcaniclastic sediments.Raymond, O.L., Liu, S., Gallagher, R., Zhang, W., Highet, L.M. Surface Geology of Australia 1:1 million scale dataset 2012 edition.
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The Itcha Range as seen from the south During the mafic capping stage, basanite, alkali olivine basalt and hawaiite erupted mainly from small parasitic cones, tuff rings and fissures in the eastern half of the shield. Eruptions occurred subglacially, subaqueously and/or subaerially as shown by a wide range in the degree of vesicularity, freshness and glass content of the lavas. In most cases, each parasitic cone produced three or four lava flows from breaches in the cone walls. These were erupted as pāhoehoe and ʻaʻā, but the tops of the lava flows are commonly missing due to erosion.
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The "Lydian Stone" known to the Ancient Greeks is named for the ancient kingdom of Lydia in what is now western Turkey. A similar rock type occurs in New England. Such rock types have long been used for the making of touchstones to test the purity of precious metal alloys, because they are hard enough to scratch such metals, which, if drawn (scraped) across them, show to advantage their metallic streaks of various (diagnostic) colours, against the dark background. There are, confusingly, not one but two rocks called Basanite, one being a black form of jasper and the other a black volcanic rock closely akin to basalt.
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This is because the peralkaline content of these felsic lavas decreased the viscosity of the flows a minimum of 10–30 times over that of calc-alkaline felsic flows. Evidence for explosive volcanism exists in the form of pumice flows, bedded tuffs, intensely shattered basement rocks and the high content of coarse basement clasts in rhyolite breccias. Magma production of the Anahim hotspot has shifted from more felsic to more mafic compositions in the last 3.0 million years. For instance, much of the magma created between 3.0 and 0.33 million years ago was igneous phonolite, trachyte, trachyandesite, basalt and basanite; the volcanoes built during this period are almost entirely made of these rock types.
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Dredging has produced basaltic and carbonatic rocks that are partly covered by ferromanganese crusts or chemically altered by phosphate. In addition, shallow water calcarenites, conglomerates, coral debris, hemipelagic sediments, breccia, limestones, felsite, foraminiferal sand, pelagic ooze, reefal limestones and sediments have been recovered. The volcanic rocks include alkali basalts, basanite, hyaloclastite, palagonite, picrite, pumices, basaltic tuffs, trachybasalt and trachyte and define an alkaline ocean island basalt suite although the existence of tholeiites as in Hawaii is possible and substantial amounts of evolved volcanic rocks have been recovered; these were probably generated by basaltic melts in magma chambers. Minerals contained in the rocks include mafic clots, amphibole, apatite, clinopyroxene including augite, olivine, plagioclase, spinel and titanomagnetite.
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Although extensive rifting has not yet been recognized in the Northern Cordilleran Volcanic Province, volcanism throughout the past 1.6 million years is possibly due to repetitive upper mantle upwelling and adjacent transtension throughout the Queen Charlotte Fault, accommodated partly by numerous east-west trending fault zones that extend all through the Northern Cordilleran Volcanic Province. The volcanics comprising the Northern Cordilleran Volcanic Province are consistent with the rifting environment. Alkaline basalt, lesser hawaiite and basanite magmas from effusive eruptions create the massive shield volcanoes and small cinder cones throughout the volcanic province, several of which comprise lherzolite magma. Felsic magmas from more viscous eruptions create the massive central volcanoes and largely consist of trachyte, pantellerite and comendite lavas.
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Minor and major volcanoes of the Northern Cordilleran Volcanic Province, including the Queen Charlotte, Denali and Tintina fault zones A range of more heavily alkaline rock types not commonly found in the Western Cordillera are regionally widespread in the Northern Cordilleran Volcanic Province. These include nephelinite, basanite and peralkaline phonolite, trachyte, and comendite lavas. The most magnesium oxide-rich nephelinites, basanites and alkaline basalts all through the Northern Cordilleran Volcanic Province display trace element abundances and isotopic compositions that are logical with an asthenospheric source like those for average oceanic island basalt and for alkaline basalts younger than five million years in the rift-related Basin and Range Province of southwestern United States and northwestern Mexico. One hypothesized explanation for oceanic island basalt in the Earth's upper mantle under the Northern Cordilleran Volcanic Province is the existence of a slab window.
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