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Major-element, trace-element and O-isotope analyses were carried out for garnetiferous Ti–clinohumite rocks and eclogites from the Kumdy Kol area, as well as talc–kyanite–phengite–almandine schists (previously named as whiteschists) and eclogites from the Kulet area of the Kokchetav ultrahigh-pressure (UHP) terrane, to explore their possible origins. Both garnetiferous Ti–clinohumite rocks and talc–kyanite–phengite–almandine...
Pb isotopic data are presented for hybrid rocks formed by mingling between mantle-derived tholeiitic magma of the Eocene Miki Fjord macrodike (East Greenland) and melt derived from the adjacent Precambrian basement. Bulk mixing and AFC processes between end-members readily identified in the field fail to model the Pb isotope systematics. Selective contamination during diffusional exchange, which can...
Carbonatites are known to contain the highest concentrations of rare-earth elements (REE) among all igneous rocks. The REE distribution of carbonatites is commonly believed to be controlled by that of the rock-forming Ca minerals (i.e., calcite, dolomite, and ankerite) and apatite because of their high modal content and tolerance for the substitution of Ca by light REE (LREE). Contrary to this conjecture,...
We present major and trace element data of olivine (Fo 86–91 ) — hosted melt inclusions from five Island Arc Basalt (IAB) lavas from Marsili seamount, a large volcano in the active Marsili back-arc basin of the Southern Tyrrhenian. The geochemical composition of this suite of melt inclusions varies widely, extending the range of variation of the host lavas and providing further insights into...
The Qinling molybdenum belt is a prominent metallogenic structure in central China hosting several significant porphyry- and porphyry–skarn-type deposits. The Huanglongpu Mo deposit in the north-western part of the belt is unique in that it is associated with carbonatite dykes, rather than felsic magmatism. The carbonatites are composed largely of Sr–Mn-rich calcite and characterized by high concentrations...
We determined plagioclase-melt partition coefficients for 18 elements by performing controlled cooling rate, 1-atmosphere experiments using both natural and synthetic basaltic (51wt.% SiO 2 ) and basaltic andesite (56wt.% SiO 2 ) powders in a vertical quench furnace. The experiments produced An 69 to An 87 composition plagioclase. Three starting powders were Gorda Ridge...
The Lower to Middle Jurassic Mudurnu formation of the Sakarya Zone (Northern Turkey) was deposited in an extensional basin. This unit crops out along the southern Pontide range and consists of marine sedimentary rocks including debris flows, lignite-bearing clastic rocks and Ammonitico Rosso horizons alternating with mafic and felsic volcanic and volcaniclastic rocks. Magmatic rocks of the Mudurnu...
Oldoinyo Lengai and the volcanic centres of the Lake Natron–Engaruka province contain melilite as a widespread mineral. Extraordinarily Na–Al-rich melilites (up to 6wt.% Na 2 O and 9wt.% Al 2 O 3 ) from recent explosive eruptions are among the most Na-rich ever reported. Their unusual mineral composition leads to optical properties with vivid birefringence colours of 2nd order...
Abundant mantle xenoliths are found in widespread undersaturated Cenozoic basaltic rocks in Northeastern Tasmania and comprise lavas, dykes, plugs and diatremes. The basanites and nephelinites, include primitive magmas (11–14wt.% MgO) with OIB-like geochemical features. Trace element and Pb– and Sr–Nd isotope data suggest that they were generated by mixing of melts derived from low degree (<5%)...
The Tianshan rodingite was formed from eclogite tectonically included in ultramafic rocks of the Changawuzi ophiolite in the southwestern Tianshan, China. Rodingites derived from eclogite contain a mineral assemblage of prehnite, clinozoisite, hydrogrossular, diopside, vesuvianite, chlorite and minor zircon. Pervasive rodingitization took place during exhumation of the subducted slab under conditions...
The Llano Uplift of central Texas is a gentle structural dome exposing ∼1370 to 1230Ma metaigneous and metasedimentary rocks of Grenville affinity along the southern margin of Laurentia. The metamorphic rocks were subsequently intruded by ∼1119 to 1070Ma late syn- to post-tectonic granites collectively known as the Town Mountain Granite (TMG). The eastern most of the TMG, the Marble Falls (MF), Kingsland...
The compositional variation of clinopyroxene and the partitioning of major elements between clinopyroxene and melt are estimated as a function of the cooling rate. Clinopyroxenes were crystallized under variable cooling regimes (15, 9.4, 3, 2.1, and 0.5°C/min from 1250 down to 1000°C) and at isothermal conditions of 1000°C from a basaltic composition at a pressure of 500MPa under anhydrous and hydrous...
Macro- and micro-scale structures, fluid inclusions, quartz rheology and host mineral chemistry were used to establish the P–T–d evolutionary path of monometamorphic metapelites of the Schneeberg Fault Zone. Four selected quartz generations indicate formation conditions during stages of prograde and retrograde metamorphism. Earliest foliation development S1 is outlined by quartz foam microstructures...
In the central Rhodope mountains of Greece a carbonate-bearing metaperidotite lens ∼200×500m in size crops out as part of the high- to ultrahigh-pressure metamorphic Upper Sidironero Complex ∼500m SE of the Gorgona Village, north of Xanthi town. It is composed primarily of coarse grained (3–20mm in size) olivine and orthopyroxene, medium grained clinohumite and medium to fine grained tremolite, chlorite,...
The Catalão I carbonatite complex is part of the Late-Cretaceous Alto Paranaíba Igneous Province (APIP) and consists of a multi-intrusion body zoned from bebedourite–(pyroxenite)-series rocks at the border to carbonatite- and phoscorite-series rocks at the core. The phoscorites consist of apatite, magnetite, and a Mg-silicate (phlogopite or olivine) and are subdivided into early-stage; olivine-bearing...
The Chagai–Raskoh arc is located in western Pakistan and extends into Iran and Afghanistan. The arc forms an elongate body trending EW and is roughly 500km long by 150km wide. Activity along the arc began in the Late Cretaceous and continued through into the Quaternary.The oldest volcanic rocks in the arc belong to the Sinjrani and Kuchakki Formations. These rocks are primarily basalts and andesites...
Grande Ronde Basalt (GRB) lavas represent the most voluminous eruptive pulse of the Columbia River–Snake River–Yellowstone hotspot volcanism. With an estimated eruptive volume of 150,000km 3 , GRB lavas form at least 66% of the total volume of the Columbia River Basalt Group. New 40 Ar/ 39 Ar dates for GRB lavas reveal they were emplaced within a maximum period of 0.42±0.18My...
Metasedimentary rocks of the Pyeongan Supergroup in the northeastern flank of the Taebaeksan Basin, South Korea, commonly contain two Al 2 SiO 5 polymorphs (And+Ky and And+Sil), or more rarely, three coexisting Al 2 SiO 5 polymorphs. Lower-grade rocks preserve chloritoid+andalusite±kyanite in muscovite–chlorite phyllite, and higher-grade rocks contain andalusite+sillimanite...
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