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Selected outcrops of the metapelitic migmatites of the Turku area (southwestern Finland) have been investigated for their petrographic and chemical properties. Three different leucosome types could be distinguished: leucosome sills, in-situ leucosomes, and composite leucosomes. Almost all leucosomes are rich in Or-dominated alkali feldspar, only a few composite leucosomes show plagioclase-rich layers...
Anatectic migmatites commonly show both prograde (entropy producing) and retrograde reactions between minerals and melt. The final textures, mineral modes and mineral chemistries are affected by four successive processes: (i) prograde partial melting and small-scale segregation into melt-rich domains and restitic domains; (ii) partial melt extraction; (iii) partial retrograde reactions (back reaction)...
The study of volatile elements in crustal anatectic terranes may provide information about the role of fluid flow and fluid pathways during high temperature metamorphism. We have studied the distribution of Li and B in two migmatitic areas: the Pena Negra Anatectic Complex (central Spain) and the migmatites and leucogranites associated with the Ronda peridotites (southern Spain). They represent two...
Clockwise pressure-temperature (P-T) paths of metamorphism pass through two kinds of melting reactions with increasing temperature. The first generates H 2 O-saturated partial melts at the H 2 O-saturated solidus, only if excess H 2 O is present. Usually, this accounts for less than 3% melt. The second generates H 2 O-undersaturated melts through dehydration-melting...
Recent results of studies aimed to determine the water solubilities and the liquidus temperatures in synthetic and natural granitic systems are used to constrain the minimum water contents of granitic melts generated in the crust as a function of pressure, temperature, melt composition, and water activity. It is concluded that melts generated in the crust at high temperature and low water activities...
Pelitic and semi-pelitic granulites from Namaqualand, South Africa underwent dehydration melting and developed leucosome domains in which large garnets are intimately associated with coarse-grained quartz in lobate embayments and inclusions. Local retrograde replacement of leucosome anhydrous phases by coarse biotite and/or sillimanite is not uncommon, but is far from universally developed. Also developed...
The eclogites from the western segment of the Altyn Tagh occur as lens or boundins within quartzofeldspathic gneisses or pelitic gneisses characterized by amphibolite facies parageneses. The petrographic features and reaction textures testify to three main metamorphic stages: (1) the peak eclogite facies stage (P>15 kbar, T=665-880 o C), (2) the granulitic facies stage (P=11-14 kbar, T=670-800...
The high pressure, low temperature metamorphic rocks of the structurally deepest regions of Saih Hatat, NE Oman exhibit an eastward increase in metamorphic grade from epidote blueschist facies conditions in central Saih Hatat to eclogitic conditions along the eastern coast. Mineral assemblages in these rocks allow the application of one or two reliable experimentally calibrated geobarometers, which...
The Cowra Granodiorite is a relatively mafic, enclave-rich, S-type pluton in the Lachlan Fold Belt, which has been cited as a type example of a restitic origin for all varieties of enclaves in Lachlan Fold Belt S-type granites. Microgranitoid enclaves from the pluton are subordinate to metasedimentary varieties and can be subdivided into two groups according to their mafic mineral assemblage: pyroxene...
This study reports new geochemical and Sr-Nd-Pb isotopic data for Miocene to Quaternary basaltic to andesitic, dacitic, and rhyolitic volcanic rocks from the Huichapan caldera, located in the central part of the Mexican Volcanic Belt (MVB). The initial Sr and Nd isotopic ratios, except for one rhyolite, range as follows: 87 Sr/ 86 Sr 0.70357-0.70498 and 143...
Upper Cretaceous-Paleocene calc-alkaline dacitic and rhyodacitic lava flows and domes are exposed in the Saraykent (Yozgat) region within Central Anatolian Crystalline Complex (CACC). Saraykent volcanics are generally plagioclase+hornblende+biotite+titanomagnetite+/-quartz+/-augite-phyric. Subrounded, vesicular magmatic enclaves, ranging from a few millimeters to a few centimeters in size, are present...
Miocene to Quaternary mafic (SiO 2 <54 wt.%) and evolved (SiO 2 >54 wt.%) lavas from Samburu Hills, northern Kenya rift, exhibit significant variations in major and trace element compositions, and Sr-Nd isotopic ratios. Bimodal lavas were erupted in the early and middle Miocene (20-15 Ma and 15-10 Ma) and Pliocene (4.1-3.6 Ma), whereas only mafic lavas were produced in the upper...
This study is an attempt to unravel the tectono-metamorphic history of high-grade metamorphic rocks in the Eastern Erzgebirge region. Metamorphism has strongly disturbed the primary petrological genetic characteristics of the rocks. We compare geological, geochemical, and petrological data, and zircon populations as well as isotope and geochronological data for the major gneiss units of the Eastern...
Deep-seated xenoliths entrained in the Hannuoba basalts of the northern Sino-Korean Craton include mafic and felsic granulites, mantle wall-rock from spinel- and garnet-spinel peridotite facies, and basaltic crystallisation products from the spinel-pyroxenite and garnet-pyroxenite stability fields. The mineral compositions of the xenoliths have been used to estimate temperatures and, where possible,...
The paper presents the results from a reconnaissance investigation of carbonatites in a newly discovered alkaline complex in the Kola peninsula, Russia. The Kandaguba complex differs from other carbonatite plutons of the Kola alkaline province by (a) the absence of ultrabasic rocks, (b) widespread occurrence of nepheline-, cancrinite- and nepheline-cancrinite syenites and carbonatites and (c) presence...
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