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27-650: [REDACTED] Look up 馬鞍山  or 马鞍山 in Wiktionary, the free dictionary. Ma On Shan may refer to: Ma On Shan (peak) (simplified Chinese: 马鞍山 ; traditional Chinese: 馬鞍山 ; lit. 'saddle peak'), a mountain in the New Territories of Hong Kong Ma On Shan (town) , a New Town in the New Territories on the foot of Ma On Shan mountain Ma On Shan line , now part of Tuen Ma line,

54-648: A soil amendment . Rhyolite is an extrusive igneous rock, formed from magma rich in silica that is extruded from a volcanic vent to cool quickly on the surface rather than slowly in the subsurface. It is generally light in color due to its low content of mafic minerals, and it is typically very fine-grained ( aphanitic ) or glassy . An extrusive igneous rock is classified as rhyolite when quartz constitutes 20% to 60% by volume of its total content of quartz, alkali feldspar , and plagioclase ( QAPF ) and alkali feldspar makes up 35% to 90% of its total feldspar content. Feldspathoids are not present. This makes rhyolite

81-415: A composition very close to the water-saturated granite eutectic and with extreme enrichment in most incompatible elements . However, they are highly depleted in strontium , barium , and europium . They are interpreted as products of repeated melting and freezing of granite in the subsurface. HSRs typically erupt in large caldera eruptions. Rhyolite is common along convergent plate boundaries , where

108-561: A natural glass or vitrophyre, also called obsidian . Slower cooling forms microscopic crystals in the lava and results in textures such as flow foliations , spherulitic , nodular , and lithophysal structures. Some rhyolite is highly vesicular pumice . Peralkaline rhyolites (rhyolites unusually rich in alkali metals) include comendite and pantellerite . Peralkalinity has significant effects on lava flow morphology and mineralogy , such that peralkaline rhyolites can be 10–30 times more fluid than typical calc-alkaline rhyolites. As

135-837: A railway line in Hong Kong Ma On Shan station , an elevated train station in Hong Kong Ma On Shan Village , a historic mining village in Hong Kong See also [ edit ] All pages with titles beginning with Ma On Shan Ma'anshan (simplified Chinese: 马鞍山 ; traditional Chinese: 馬鞍山 ; pinyin: Mǎ'ānshān ), a city in Anhui Province, People's Republic of China Maanshan Nuclear Power Plant in Pingtung County, Taiwan Topics referred to by

162-595: A result of their increased fluidity, they are able to form small-scale flow folds, lava tubes and thin dikes. Peralkaline rhyolites erupt at relatively high temperatures of more than 1,200 °C (2,190 °F). They comprise bimodal shield volcanoes at hotspots and rifts (e.g. Rainbow Range , Ilgachuz Range and Level Mountain in British Columbia , Canada). Eruptions of rhyolite lava are relatively rare compared to eruptions of less felsic lavas. Only four eruptions of rhyolite have been recorded since

189-633: A result, many eruptions of rhyolite are highly explosive, and rhyolite occurs more frequently as pyroclastic rock than as lava flows . Rhyolitic ash flow tuffs are the only volcanic product with volumes rivaling those of flood basalts . Rhyolites also occur as breccias or in lava domes , volcanic plugs , and dikes . Rhyolitic lavas erupt at a relatively low temperature of 800 to 1,000 °C (1,470 to 1,830 °F), significantly cooler than basaltic lavas, which typically erupt at temperatures of 1,100 to 1,200 °C (2,010 to 2,190 °F). Rhyolites that cool too quickly to grow crystals form

216-672: A slab of oceanic lithosphere is being subducted into the Earth's mantle beneath overriding oceanic or continental lithosphere . It can sometimes be the predominant igneous rock type in these settings. Rhyolite is more common when the overriding lithosphere is continental rather than oceanic. The thicker continental crust gives the rising magma more opportunity to differentiate and assimilate crustal rock. Rhyolite has been found on islands far from land, but such oceanic occurrences are rare. The tholeiitic magmas erupted at volcanic ocean islands, such as Iceland , can sometimes differentiate all

243-619: Is different from Wikidata All article disambiguation pages All disambiguation pages Ma On Shan (peak) Beneath the west face of the mountain along Tolo Harbour , the Ma On Shan new town extension, administratively part of Sha Tin , is named after the hill. It ends north in Wu Kai Sha . Ma On Shan can be distinguished by the west face which looks like a saddle, and "Ma On Shan" can be translated as "horse saddle mountain". Nine streams flow down from Ma On Shan, with

270-462: Is more often erupted as pyroclastic rock than as lava flows . Rhyolitic ash-flow tuffs are among the most voluminous of continental igneous rock formations. Rhyolitic tuff has been used extensively for construction. Obsidian , which is rhyolitic volcanic glass , has been used for tools from prehistoric times to the present day because it can be shaped to an extremely sharp edge. Rhyolitic pumice finds use as an abrasive , in concrete , and as

297-521: Is the most silica -rich of volcanic rocks . It is generally glassy or fine-grained ( aphanitic ) in texture , but may be porphyritic , containing larger mineral crystals ( phenocrysts ) in an otherwise fine-grained groundmass . The mineral assemblage is predominantly quartz , sanidine , and plagioclase . It is the extrusive equivalent of granite . Its high silica content makes rhyolitic magma extremely viscous . This favors explosive eruptions over effusive eruptions , so this type of magma

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324-761: The Chinese Lily ( Lilium brownii ) which is found on the mountain's eastern slope. A few types of wild orchid grow in the streams of Ma On Shan, including Hong Kong's most common orchid, the Bamboo Orchid , so called because its distinctive stem resembles bamboo. The natural environment of Ma On Shan is relatively undisturbed, so this valuable sanctuary gives shelter to many wildlife species. Common mammals are Chinese pangolin ( Manis pentadactyla ), Chinese porcupine ( Hystrix brachyura ), wild boar ( Sus scrofa ) and common muntjac ( Muntiacus muntjac ). The north and north-east slopes of The Hunch Backs and

351-620: The R field of the TAS diagram . The alkali feldspar in rhyolites is sanidine or, less commonly, orthoclase . It is rarely anorthoclase . These feldspar minerals sometimes are present as phenocrysts. The plagioclase is usually sodium -rich ( oligoclase or andesine ). Cristobalite and trydimite are sometimes present along with the quartz. Biotite , augite , fayalite , and hornblende are common accessory minerals. Due to their high content of silica and low iron and magnesium contents, rhyolitic magmas form highly viscous lavas . As

378-526: The biggest located on the southwest slope of Ma On Shan, near Ma On Shan Village . A group of villages located east of the peak is named Shap Sze Heung and the harbour of Three Fathoms Cove . The saddle-like peaks of Ma On Shan is formed by volcanic rocks , much like many of the tallest mountains in Hong Kong, such as Tai Mo Shan . The base of the mountain is mostly formed by sedimentary rocks around 120 - 60 million years ago. The southeastern part of

405-556: The east slope of Ma On Shan, covering an area of 118 hectares, was designated as a Site of Special Scientific Interest in 1976. In the 1850s, the Wans, a Hakka family, established the Ma On Shan Village . They lived traditional lives of farming. Once iron mining became prominent on the mountain in the 1950s, the villagers slowly transitioned to make a living through mining. As farming was no longer necessary in Hong Kong at

432-508: The extrusive equivalent of granite. However, while the IUGS recommends classifying volcanic rocks on the basis of their mineral composition whenever possible, volcanic rocks are often glassy or so fine-grained that mineral identification is impractical. The rock must then be classified chemically based on its content of silica and alkali metal oxides ( K 2 O plus Na 2 O ). Rhyolite is high in silica and total alkali metal oxides, placing it in

459-446: The mountain consists of intruded rhyolite . Some shorter mountains in Hong Kong are formed by older Granitic rocks. The saddle shape of Ma On Shan was formed over the past 200 million years. Originally, Ma On Shan was a surface of sedimentary rocks covered by volcanic rocks (mainly tuffs ) from volcanic eruptions (about 160 mya ). The sedimentary and volcanic rocks were then folded into ridges (about 120 mya). Rhyolite rocks intruded

486-434: The rhyolite appears to be a product of melting of crustal sedimentary rock. Water vapor plays an important role in lowering the melting point of silicic rock, and some rhyolitic magmas may have a water content as high as 7–8 weight percent. High-silica rhyolite (HSR), with a silica content of 75 to 77·8% SiO 2 , forms a distinctive subgroup within the rhyolites. HSRs are the most evolved of all igneous rocks, with

513-617: The ridge later (about 100 mya). The faulting in the ridges then lead to a more saddle-like shape (about 60 mya). The weathering process made the ridges and peaks smooth (about 60 mya - now). The north slope of Ma On Shan is mostly tree-covered, while the south slope is mainly shrubs and grasses. On these hostile volcanic hills, only hardy and highly adaptable plants survive. There are some rare flora species, including Rhododendron simsii , which blooms with red flowers in late March, and two other species of native Rhododendron . Rare and protected species of plants also grow on Ma On Shan including

540-573: The same term [REDACTED] This disambiguation page lists articles associated with the title Ma On Shan . If an internal link led you here, you may wish to change the link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=Ma_On_Shan&oldid=1184213710 " Categories : Disambiguation pages Place name disambiguation pages Hidden categories: Articles containing simplified Chinese-language text Articles containing traditional Chinese-language text Short description

567-576: The start of the 20th century: at the St. Andrew Strait volcano in Papua New Guinea and Novarupta volcano in Alaska as well as at Chaitén and Cordón Caulle volcanoes in southern Chile . The eruption of Novarupta in 1912 was the largest volcanic eruption of the 20th century, and began with explosive volcanism that later transitioned to effusive volcanism and the formation of a rhyolite dome in

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594-545: The time, these villages were abandoned one by one. Iron mining on Ma On Shan started in the early 1900s. Its high-purity (60%) iron ore attracted many newcomers to live near Ma On Shan in the late 1940s. The number of these mining newcomers exceeded 5,000 in the 1950s, with annual output in the 1950s and 1960s exceeding 100,000 tonnes. During this peak in the mining of iron, most of the miners lived in Ma On Shan New Village. An extensive network of tunnels

621-450: The vent. Rhyolite magmas can be produced by igneous differentiation of a more mafic (silica-poor) magma, through fractional crystallization or by assimilation of melted crustal rock ( anatexis ). Associations of andesites , dacites , and rhyolites in similar tectonic settings and with similar chemistry suggests that the rhyolite members were formed by differentiation of mantle-derived basaltic magmas at shallow depths. In other cases,

648-655: The way to rhyolite, and about 8% of the volcanic rock in Iceland is rhyolite. However, this is unusual, and the Hawaiian Islands (for example) have no known occurrences of rhyolite. The alkaline magmas of volcanic ocean islands will very occasionally differentiate all the way to peralkaline rhyolites, but differentiation usually ends with trachyte . Small volumes of rhyolite are sometimes erupted in association with flood basalts , late in their history and where central volcanic complexes develop. The name rhyolite

675-470: Was built under the hill. However, in the 1970s, Japan’s demand for iron was reduced massively due to them building oil tankers. Therefore, the mining operations in Ma On Shan became unprofitable and uncompetitive. The iron mines were abandoned in 1976. Until 2006, there are still 30,000 tonnes of iron ore in Ma On Shan. Rhyolite Rhyolite ( / ˈ r aɪ . ə l aɪ t / RY -ə-lyte )

702-657: Was introduced into geology in 1860 by the German traveler and geologist Ferdinand von Richthofen from the Greek word rhýax ("a stream of lava") and the rock name suffix "-lite". In North American pre-historic times , rhyolite was quarried extensively in what is now eastern Pennsylvania . Among the leading quarries was the Carbaugh Run Rhyolite Quarry Site in Adams County . Rhyolite

729-567: Was mined there starting 11,500 years ago. Tons of rhyolite were traded across the Delmarva Peninsula , because the rhyolite kept a sharp point when knapped and was used to make spear points and arrowheads. Obsidian is usually of rhyolitic composition, and it has been used for tools since prehistoric times. Obsidian scalpels have been investigated for use in delicate surgery. Pumice, also typically of rhyolitic composition, finds important uses as an abrasive , in concrete , and as

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