Effusive Rocks

Vollmer 1976, 1977 Hawkesworth and Vollmer 1979). Oxygen isotopic composition is high with 518Osmow +13%o (Turi and Taylor 1976). 

Monte Amiata is a 1738 m-high cone dominated by trachydacitic lava flows and domes with a few late-erupted shoshonites and latites. Magmatism is 0.3 to 0.2 Ma and is associated with well-known and long-exploited cinnabar mineralisations (Mazzuoli and Pratesi 1963 Barberi et al. 1971 van Bergen 1985 Ferrari et al. 1996 and references therein). The Monte Amiata trachydacites exhibit a porphyritic texture with abundant 

The largest intrusion is represented by the Monte Capanne monzogran-itic stock (about 10 km in diameter), located in the western side of the island. It exhibit a porphyritic texture with centimetre- to decimetre-sized euhedral megacrysts of K-feldspar that are set in a medium- to coarsegrained matrix formed by variable amounts of plagioclase, quartz, K-feldspar and biotite with accessory apatite, zircon, monazite, ilmenite, and tourmaline. The intrusion contains abundant microgranular calc-alkaline 

The Gavorrano intrusive rocks consist of 4.9 to 4.3 Ma syenogranites, alkali-feldspar granites and monzogranites that are mostly hidden below 

208Pb/204Pb = 38.87 to 39.11), but the highest values are found in the high-radiogenic Sr group (Pinarelli 1991). 

---

Ergnss, m. effusion, discharge, overflow, -ge- stein, n. effusive rock, erh., abbTev. (erhitzt) heated. 

QUARTZ PORPHYRY. One of the hypabyssal or effusive rocks chemically related to the granite or alkali family but rich in silica, which occurs as quartz phenocrysts in a crypto or microcrystalline ground mass. 

The Tuscany Magmatic Province consists of an association of calc-alkaline to lamproitic mafic to intermediate magmas and silicic intrusive and effusive rocks. Silicic melts have been formed by crustal melting, with an important role of mixing with mantle-derived magmas. Mafic melts are of mantle origin but resemble closely some upper crustal rocks, such as metapelites, in terms of incompatible trace elements and radiogenic isotope... 

Fig. 6) they are presented in Table 1 as materials 4, 5, 6 belonging to the tuff layers. The properties of effusive rock mass are defined via material 7, and properties of interlayers consisting of andesites, diorites, porphyrites are determined by material 8 those of faults - by materials 9, 11 (properties of faults 1, D, V are determined by material 9, and the rest ones - by the 11-th material). Vertical faults penetrate the modeled area from the bottom boundary to the 3-rd layer foot. In this case, the finite-difference scheme plotting accounts for the fault thickness, which was assumed to be 5 m. The input data for numerical study were taken after a series of preliminary calculations, Krashin (2002). 

Standard zircon 91500 appears suitable to normalize the raw data of zircon grains from 300 to 2400 Ma. This covers the usual range of application of the U-Pb zircon method to date age emplacement of ordinary eruptive or effusive rocks. We reasonably think that older samples are even easier to date according to this procedure. A question arises concerning zircons much younger than 3(X) Ma what is the lower limit that can be reached using this procedure ... 

Rock wool fibers can be characterized by their acidity modulus, Mj, which describes the ratio of acidic to basic oxides. If Ms< 1.2, the fiber is called slag wool, the base material of which is cinder. Nowadays, such low quality fibers are not produced any more because they are very brittle and show a poor chemical resistance. If Mj= 1.2-1.5, the fiber is considered to be a mineral wool, the base materials of which are basic volcanic rock and cinder. These fibers are brittle, but have acceptable insulation properties, hence their significance in the construction industry is high. If Ms> 1.5, the fiber is called rock wool, and if its base material is basalt then it is named basalt wool (basalt fiber, BF). The base of basalt fiber is basalt, which is a volcanic, over-ground, effusive rock saturated with 45-52 wt.% Si02. Due to the circumstances of its formation, basalt has several excellent properties. In addition to its high elasticity modulus and excellent heat resistance. 

Igneous rocks are also called solidification, eruption or magma rocks. They are formed from the solidification of magma, a liquid rock mass in which gases can also be present. When this solidification process takes place in the earth s crust, we speak of effusive or volcanic... 

Complex (20 and 15 ka), sited north of Primordial Vulcano, is the remnant of a stratovolcano with a central caldera (Fossa Caldera), mainly formed by latitic, trachytic and rhyolitic lava flows, domes, and pyroclastic rocks. Fossa Caldera products were erupted between 15 and 8 ka by pyroclastic and effusive eruptions of shoshonitic intermediate to silicic magmas. Cono della Fossa is a 391 m high active edifice that rises at the center of the Fossa Caldera it was formed in the last 6000 years by several silicic pyroclastic eruptions and a few lava effusions. Vulcanello is a shield made of mafic potassic lavas showing a KS affinity, with central trachytic pyroclastic cones. Vulcanello was formed as a new island probably about one thousand years ago (magnetostratigrafic age by Tanguy, personal communication) sand accumulation in the isthmus area finally connected Vulcanello with the main island. 

Fig. 19. Relationship between volumes of submarine and terrestrial volcanic effusions (/) and volumes of COj (2) buried in carbonate rocks, in the area of the present continents (after Ronov).

Thus questions of the effect of pressure on mineral equilibria and the regime of water and carbon dioxide in metamorphism required additional consideration. Of special importance for the study of iron-chert, carbonate, effusive, and intrusive rocks was preliminary theoretical examination of the particulars of metamorphism in conditions of a deficit of water both in the case of low Eh o dry systems closed to water. These questions were... 

In summary, each of the various approaches by which magma systems can be imaged provides insights into the duration and dynamics of magma storage that are unique, because they are necessarily biased in some fashion. It should be reiterated that because these estimates are largely based on volcanic rocks and/or their effusion rates, an even more fundamental bias to the majority of... 

In productive basins the process of diffusion from both source rocks and reservoirs may be responsible for observed elevated background concentrations that have no apparent relationship to the known accumulations. Alternatively, the presence of free hydrocarbons effusing outward and upward in areas of microfractures and dispersed by groundwater flow could similarly account for this background. If diffusion were the... 

The igneous rocks were formed by the solidification of magma. Depending on the site of this solidification, such rocks are divided into those situated at a depth (intrusive) which were formed under the earth s surface, and igneous rocks which solidified on the surface (effusive). From the chemical standpoint, particularly with respect to the Si02 content, we can consider acid neutral and basic rocks. 

The main productive series of fractured volcanogenic-sedimentary rocks of -1270 m thickness was modeled as alternating beds of tuffs and interlayers of andesites, diorites, porphyrites. The lower series of -1600 m - effusive-pyroclastic rocks of the Paratoon suite of Myocene. The values of hydrogeologic parameters of the layers identified are presented in Table 1. Thermoconductivity coefficient of 2.0 W/m-°K was specified for the rocks in three upper layers, and 2.5 W/m °K in the rest ones, with heat capacity of 1750 J/kg-°K, density of rocks is 2500 kg/m ... 

In the central part of the Illizi Basin and over the Ghadames Depression (WT-i, HD-i, RYB-i, AKF-i) we observe sediments characteristic of deeper marine environments, i.e. fine-grained sandstones with intercalations of clays and silts. The characteristic feature of these Siegenian sandstones is the chloritic composition of the clay fraction of their cements and the chloritic-illitic nature of the argillaceous intercalations. Because of this situation, these deposits could have been derived from a hard substrate (effusive or metamorphic rocks) inundated by the Siegenian sea and open into the direction of the present Libyan coast. 

---