نتایج جستجو برای: prograde metamorphism
تعداد نتایج: 2624 فیلتر نتایج به سال:
Integrated pseudosection modeling and monazite petrochronology of paragneiss from the Kanchenjunga region of northeastern Nepal reveal the presence of cryptic tectonometamorphic discontinuities within the Himalayan metamorphic core. These new data outline a series of thrust-sense structures that juxtapose rocks that generally record a protracted history of early Eocene to latest Oligocene–early...
The conditions at which monazite and allanite were produced and destroyed during prograde metamorphism of pelitic rocks were determined in a Buchan and a Barrovian regional terrain and in a contact aureole, all from northern New England, USA. Pelites from the chlorite zone of each area contain monazite that has an inclusion-free core surrounded by a highly irregular, inclusion-rich rim. Texture...
Crystal form of almandine-rich garnets from staurolite schists of Aliabad-Damagh, changes from pure {110} to pure {211} and intermediate forms between these two end-members. Compositional zoning patterns of all forms are similar, consistent with one-step growth during prograde metamorphism. Mineral chemical data indicate that (Mn + Mg)/Ca in the ~60-micron rim of the almandine-rich garnet cryst...
TEM and XRD techniques were used to study crystal growth characteristics of the fabric-forming phyllosilicates which developed in response to low-grade metamorphism and tectonic imbrication in part of the Southern Uplands thrust terrane. Prograde regional metamorphism, ranging from late diagenesis through the anchizone to the epizone, was accompanied by the development of a slaty cleavage which...
the cheshin meta-calcareous rocks (permo triassic) in southeast hamedan outcrop in association with a variety of pelitic schists and hornfels rocks. the intrusion of the alvand batholith (jurassic age) into pelitic and calcareous host rocks has produced metamorphic rocks in the hamedan area (cheshin village). on the basis of the dominance of calcite/dolomite, silicate and ore minerals, the calc...
Analogue and computational models principally provide our present understanding of the mechanisms of prograde metamorphism and orogenesis, yet, due to the difficulty of linking prograde age information with the pressure–temperature (P–T) evolution of a rock, these models for the most part remain untested. Here, we describe an approach that allows multiple prograde pressure–temperature–time (P–T...
The calc-silicate xenoliths, within the Shir-Kuh batholith are characterized by melilite, garnet, vesuvianite, and wollastonite mineral assemblage. On the basis of paragenetic relations, prograde and retrograde metamorphism are involved in the formation of these minerals. Melilite, wollastonite and diopside formed during progressive metamorphism which was accompanied by thermal peak shocking a...
Recent work in Barrovian metamorphic terranes has found that rocks experience peak metamorphic temperatures across several grades at similar times. This result is inconsistent with most geodynamic models of crustal over-thickening and conductive heating, wherein rocks which reach different metamorphic grades generally reach peak temperatures at different times. Instead, the presence of addition...
Siah-Kamar hornfalses and skarns are located about 5Km east of Dehsalm and 85Km west of Nehbandan city, southeast of Birjand Province and east of Lut Block. This Skarn formed by injected Rigi granitoid (Eocene age) into limestone and sandstone (Upper Cratacious). Rigi Mountain is mainly granodiorite in composition and contains plagioclase, quartz, hornbelend and biotite minerals. Geochemistry ...
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