scholarly journals The ammonium content in the Malayer igneous and metamorphic rocks (Sanandaj-Sirjan Zone, Western Iran)

2011 ◽  
Vol 62 (2) ◽  
pp. 171-180 ◽  
Author(s):  
Vahid Ahadnejad ◽  
Ann Hirt ◽  
Mohammad-Vali Valizadeh ◽  
Saeed Bokani
Keyword(s):  
Colorimetric Method ◽  
Igneous Rocks ◽  
Granitic Rocks ◽  
Metamorphic Rocks ◽  
Low Grade ◽  
High Concentration ◽  
Western Iran ◽  
Metasedimentary Rocks ◽  
Sanandaj Sirjan Zone ◽  
External Sources

The ammonium content in the Malayer igneous and metamorphic rocks (Sanandaj-Sirjan Zone, Western Iran)The ammonium (NH4+) contents of the Malayer area (Western Iran) have been determined by using the colorimetric method on 26 samples from igneous and metamorphic rocks. This is the first analysis of the ammonium contents of Iranian metamorphic and igneous rocks. The average ammonium content of metamorphic rocks decreases from low-grade to high-grade metamorphic rocks (in ppm): slate 580, phyllite 515, andalusite schist 242. In the case of igneous rocks, it decreases from felsic to mafic igneous types (in ppm): granites 39, monzonite 20, diorite 17, gabbro 10. Altered granitic rocks show enrichment in NH4+(mean 61 ppm). The high concentration of ammonium in Malayer granites may indicate metasedimentary rocks as protoliths rather than meta-igneous rocks. These granitic rocks (S-types) have high K-bearing rock-forming minerals such as biotite, muscovite and K-feldspar which their potassium could substitute with ammonium. In addition, the high ammonium content of metasediments is probably due to inheritance of nitrogen from organic matter in the original sediments. The hydrothermally altered samples of granitic rocks show highly enrichment of ammonium suggesting external sources which intruded additional content by either interaction with metasedimentary country rocks or meteoritic solutions.

Significance of “gneissic” rocks in the Liscomb Complex, Nova Scotia

2010 ◽  
Vol 47 (6) ◽  
pp. 927-940 ◽  
Author(s):  
J. V. Owen ◽  
R. Corney ◽  
J. Dostal ◽  
A. Vaughan
Keyword(s):  
Igneous Rocks ◽  
Metamorphic Rocks ◽  
Low Grade ◽  
High Grade ◽  
Peraluminous Granite ◽  
Isotopic Signatures ◽  
Conventional View ◽  
Basement Rocks ◽  
Mineral Assemblages ◽  
Intrusive Rocks

The Liscomb Complex comprises Late Devonian intrusive rocks (principally peraluminous granite) and medium- to high-grade metamorphic rocks (“gneisses”) that collectively are hosted by low-grade (greenschist facies) metasediments of the Cambro-Ordovician Meguma Group. The conventional view that these “gneisses” contain high-grade mineral assemblages and represent basement rocks has recently been challenged, and indeed, some of the rocks previously mapped as gneisses, particularly metapelites, have isotopic compositions resembling the Meguma Group. Amphibole-bearing enclaves in the Liscomb plutons, however, are isotopically distinct and in this regard resemble xenoliths of basement gneisses in the Popes Harbour lamprophyre dyke, south of the Liscomb area. Metasedimentary enclaves with Meguma isotopic signatures can contain garnets with unzoned cores (implying high temperatures) that host high-grade minerals (prismatic sillimanite, spinel, and (or) corundum) and are enclosed by retrograde-zoned rims. These features are interpreted here as having formed during and following the attainment of peak temperatures related to Liscomb magmatism. The amphibole-bearing meta-igneous rocks described here contain cummingtonite or hornblendic amphibole and occur as enclaves in granodioritic to tonalitic plutons. They are mineralogically, texturally, and isotopically distinct from Meguma metasediments and at least some of the plutonic rocks that enclose them, so remain the most likely candidate for basement rocks in the Liscomb Complex.

Fe-Mn phosphate associations as indicators of the magmatic-hydrothermal and supergene evolution of the Jálama batholith in the Navasfrías Sn-W District, Salamanca, Spain

2012 ◽  
Vol 76 (1) ◽  
pp. 1-24 ◽  
Author(s):  
T. Llorens ◽  
M.C. Moro
Keyword(s):  
Hydrothermal Fluids ◽  
Granitic Pegmatite ◽  
Metamorphic Rocks ◽  
Low Grade ◽  
Magmatic Differentiation ◽  
Metasedimentary Rocks ◽  
Quartz Veins ◽  
Ore Minerals

AbstractThe residual melts that remained after the consolidation of the Jálama batholith crystallized to form a group of intra-granitic pegmatite dykes, which are hosted by its outermost facies (the External Unit), and the most evolved residual melts migrated through fractures to form the Cruz del Rayo field of pegmatite dykes, which are hosted by pre-Ordovician low-grade metasedimentary rocks. The increasing activity of phosphorus as magmatic differentiation took place led to the crystallization of primary phosphates, including members of the triplite–zwieselite and the amblygonite–montebrasite series. A strong albitization of the granitic and pegmatite rocks led to the replacement of the primary assemblage by other phosphates such as alluaudite. The influx of post-magmatic hydrothermal fluids, produced quartz veins, gave rise to the crystallizationof ore minerals and triplite, and altered the granites, aplites and pegmatites, replacing some of the phosphate minerals and feldspars and depositing goyazite, montebrasite and childrenite–eosphorite. The interaction of the residual hydrothermal fluids with those from the surrounding metamorphic rocks during later alteration events resulted in the influx of large quantities of Ca and Mg, and produced phosphate assemblages enriched in those elements. Finally, late goyazite, hydroxylapatite and an unidentified Fe-rich phosphate were formed as a result of supergene alterationby percolating meteoric waters, which added Ca, Sr and other elements into the system, and increased fO2.

Petrology of a supra-subduction zone ophiolite (Elaz1g, Turkey)

2000 ◽  
Vol 37 (10) ◽  
pp. 1411-1424 ◽  
Author(s):  
Melahat Beyarslan ◽  
A Feyzi Bingöl
Keyword(s):  
Upper Cretaceous ◽  
Middle Eocene ◽  
Volcanic Rocks ◽  
Island Arc ◽  
Granitic Rocks ◽  
Late Triassic ◽  
Geochemical Data ◽  
Metamorphic Rocks ◽  
Low Grade ◽  
Magmatic Suite

The Elaz1g region in eastern Taurus, Turkey, exposes Paleozoic-Tertiary metamorphic, magmatic, and sedimentary units. Contacts between the different units are mostly tectonic, but there are also primary sedimentary, and intrusive contacts. The metamorphic rocks of the Elaz1g region are the Bitlis-Pütürge and Keban-Malatya massifs, which are a single tectonostratigraphic unit that has been tectonically disrupted and fragmented during the Upper Cretaceous. Magmatic rocks in the region are represented by ophiolitic units, magmatic arc products, and young volcanic rocks. The sedimentary units are represented by Upper Cretaceous - Tertiary marine and lacustrine sedimentary rocks. In the study area, the metamorphic units are represented by the Paleozoic Pütürge metamorphic rocks composed of phyllite, slate, mica schist, quartz-muscovite schist, calc-schist, and low-grade metamorphite. The ophiolite that is described in this paper is composed of wehrlite-pyroxenite, gabbro, diabase dykes, and dykes cutting gabbro. These units are cut by the granitic rocks of the Upper Cretaceous Elaz1g magmatic suite. The lithological and geochemical data on the rocks of Kömürhan ophiolite indicate that these rocks were derived from crystallization of an enriched mid-ocean ridge basalt (MORB)-type magma. The Kömürhan ophiolite formed in a supra-subduction spreading zone during the Cretaceous; related to this event is the north-dipping subduction of the southern branch of Neo-Tethys ocean, which began spreading in the Late Triassic. The crust was thickened by the development of an island arc and by the thrusting of the Pütürge metamorphic rocks onto this island arc in response to north-south compression during the Late Cretaceous. The magma formed by partial melting of the subducted slab giving rise to granitic rocks that cut the upper parts of the ophiolite. The ophiolite and the Elaz1g magmatic suite attained their present position after the Middle Eocene.

scholarly journals Provenance of Paleozoic very low- to low-grade metasedimentary rocks of South Tisia (Slavonian Mountains, Radlovac Complex, Croatia)

2013 ◽  
Vol 64 (1) ◽  
pp. 3-22 ◽  
Author(s):  
Vanja Biševac ◽  
Erwin Krenn ◽  
Fritz Finger ◽  
Borna Lužar-Oberiter ◽  
Dražen Balen
Keyword(s):  
Heavy Mineral ◽  
Age Dating ◽  
Heavy Minerals ◽  
Low Grade ◽  
High Concentration ◽  
Depositional History ◽  
Metasedimentary Rocks ◽  
Rock Types ◽  
Mineral Assemblages ◽  
Insight Into

Abstract Monazite age dating, detrital heavy mineral content and whole-rock geochemistry provided insight into the provenance, depositional history and paleogeological setting of the Radlovac Complex very low- to low-grade metasedimentary rocks (South Tisia, Slavonian Mountains, Croatia). Electron microprobe based Th-U-Pb dating of detrital monazite indicates a Variscan age of the protolith (330 ± 10 Ma). The detrital heavy mineral assemblages of representative metasedimentary rocks are dominated by apatite, zircon, tourmaline and rutile accompanied by minor quantity of epidote/zoisite, monazite and titanite. Judging from the heavy mineral assemblage, felsic igneous rocks served as the source material. This is consistent with the major and trace element spectrum of studied metasedimentary rocks characterized by high concentration of Th, high L + MREEs and high ratios of La/Sc, Th/Sc, La/Co, Th/Co and Th/Cr. The occurrence of magmatic monazite, zircon and xenotime and the absence of metamorphic heavy minerals suggest that granitoids, migmatites and migmatitic gneisses served as one major source for the metapsammites. Such rock types are commonly exposed in the Papuk Complex of the older surrounding complexes, while the Psunj Complex also contains metamorphic rocks. This is in good correlation with the monazite ages presented here which fits better with ages of Papuk Complex representative rocks than with those of the Psunj Complex known from the literature. Overall, data show that the Radlovac Complex represents the detritus of the local Variscan crust characterized by granitoid bodies, migmatites and migmatitic gneisses typical for the Papuk Complex.

Some observations on the use of zircon U-Pb geochronology in the study of granitic rocks

1992 ◽  
Vol 83 (1-2) ◽  
pp. 447-458 ◽  
Author(s):  
Ian S. Williams
Keyword(s):  
Igneous Rocks ◽  
Granitic Rocks ◽  
Metamorphic Rocks ◽  
Ion Microprobe ◽  
Zircon Population ◽  
Metamorphic History ◽  
Ion Probe ◽  
Isotopic Analyses ◽  
Single Zircon

ABSTRACTIn situ, microscale, U-Pb isotopic analyses of zircon using the SHRIMP ion microprobe demonstrate both the potential and the limitations of zircon U-Pb geochronology. Most zircons, whether from igneous or metamorphic rocks, need to be considered as mixed isotopic systems. In simple, young igneous rocks the mixing is principally between isotopically disturbed and undisturbed zircon. In polymetamorphic rocks, several generations of zircon growth can coexist, each with a different pattern of discordance. A similar situation exists for igneous rocks rich in inherited zircon, as these contain both melt-precipitated zircon and inherited components of several different ages. Microscale analysis by ion probe makes it possible to sample the record of provenance, age and metamorphic history commonly preserved within a single zircon population. It also indicates how the interpretation of conventionallymeasured bulk zircon isotopic compositions might be improved.

Hornblende geobarometry of the Nelson Batholith, southeastern British Columbia: tectonic implications

1991 ◽  
Vol 28 (12) ◽  
pp. 1982-1991 ◽  
Author(s):  
E. D. Ghent ◽  
J. Nicholls ◽  
P. S. Simony ◽  
J. H. Sevigny ◽  
M. Z. Stout
Keyword(s):  
British Columbia ◽  
Middle Jurassic ◽  
Pressure Difference ◽  
Country Rock ◽  
Granitic Rocks ◽  
Metamorphic Rocks ◽  
Low Grade ◽  
The South ◽  
Tectonic Implications ◽  
Model Combining

Hornblende geobarometry has been applied to granitic rocks of the Middle Jurassic Nelson Batholith, British Columbia, locally containing magmatic epidote. Geobarometry suggests equilibration pressures of less than 4.5 kbar (1 kbar = 0.1 GPa) in the northern part of the batholith, which lacks magmatic epidote. This part of the pluton shows clear magmatic intrusive relations, and the contact metamorphic rocks contain andalusite, which suggests that the equilibration and emplacement pressures are compatible.In the southern part of the batholith, granitic rocks containing magmatic epidote have equilibration pressures of 4.8–6.4 kbar. South and west of Nelson, there is a distinct contrast in pressure between the pluton and the country rock. Both the contact metamorphic rocks and the low-grade regional metamorphic rocks suggest pressures in the 2–3 kbar range.The pressure difference of about 2 kbar across the southwestern contact and the variation in pressure within the batholith can be explained by a model combining a late postequilibration upsurge (diapiric) of a deeper part of the pluton in the south, with a much later rotation and tilting of the batholith, associated with Eocene motion on the upper listric portion of the Slocan Lake Fault. The late diapiric (?) upsurge may account for the pressure contrast across the southwestern contact.

scholarly journals Mid-Cenozoic SHRIMP U-Pb detrital zircon ages from metasedimentary rocks in the North Patagonian Andes of Aysén, Chile

2021 ◽  
Vol 48 (1) ◽  
pp. 54
Author(s):  
Paulo Quezada ◽  
Francisco Hervé ◽  
Mauricio Calderón ◽  
Mark Fanning ◽  
Robert Pankhurst ◽  
...  
Keyword(s):  
High Energy ◽  
Detrital Zircons ◽  
Metamorphic Rocks ◽  
Low Grade ◽  
Metasedimentary Rocks ◽  
The North ◽  
Metamorphic Basement ◽  
Facies Variation ◽  
Detrital Zircon Ages ◽  
Patagonian Andes

Previously undated low-grade metamorphic rocks from the Puerto Cisnes-Queulat area (44°30’ S) contain detrital zircons of mid-Oligocene age (ca. 28 Ma). Their outcrops represent the easternmost occurrence of the late Oligocene to early Miocene marine volcano-sedimentary Traiguén Formation; previous correlation with the Paleozoic metamorphic basement of this sector of the North Patagonian Andes is thus refuted. A similar age and provenance were obtained for a paraconglomerate bed of the La Junta Formation ca. 80 km to the north, which is thought to represent a high-energy lateral facies variation of the Traiguén Formation. Miocene plutonic rocks of the North Patagonian Batholith intruded these metasedimentary rocks, generating a contact metamorphic aureole that reaches biotite grade and overprints a previous metamorphic fabric probably formed during closure of the Traiguén Basin. Similar young ages for metamorphic rocks located immediately west of the Liquiñe-Ofqui Fault Zone 300 km north, near Ayacara, suggest a regional pattern of earliest Neogene metamorphism and rapid exhumation in this segment of the Patagonian Andes.

scholarly journals V.—Metamorphic Rocks of Scotland and Galway

1871 ◽  
Vol 8 (84) ◽  
pp. 263-268
Author(s):  
G. H. Kinahan
Keyword(s):  
Igneous Rocks ◽  
Granitic Rocks ◽  
Metamorphic Rocks ◽  
History Of ◽  
Granitoid Rocks

It appears evident from the history of the metamorphic, granitoid, and granitic rocks of Scotland, written exactly halfa century ago by MacCulloch, that those rocks are very similar to rocks of the same classes in West Galway, Ireland. This acute observer evidently examined the Scotch rocks most minutely, as the groups, sub-groups, and varieties of his “primary rocks” are carefully classed and described. Still, however, his arrangement seems to require modification, as many of the rocks he has put among his granites seem not to be true granites, but rather granitoid rocks, due to the metamorphism of igneous rocks.

U–Pb Ages for Sphene from Early Precambrian Igneous Rocks in Northeastern Minnesota – Northwestern Ontario

1971 ◽  
Vol 8 (10) ◽  
pp. 1319-1324 ◽  
Author(s):  
E. J. Catanzaro ◽  
G. N. Hanson
Keyword(s):  
Hydrofluoric Acid ◽  
Igneous Rocks ◽  
Granitic Rocks ◽  
Low Grade ◽  
Early Precambrian ◽  
Grade Metamorphism ◽  
Northwestern Ontario ◽  
Good Agreement

Five sphene concentrates from early Precambrian igneous granitic rocks in northeastern Minnesota and northwestern Ontario give 207Pb–206Pb ages of 2680–2750 m.y., which are in good agreement with discordant U–Pb ages for zircon and whole-rock Rb–Sr ages (λβ = 1.39 × 10−11y−1) from these rocks. Three of the sphene concentrates give concordant ages, two discordant.Although the rocks have undergone at least one low-grade metamorphism, which has affected some of the K–Ar and Rb–Sr mineral ages from the region, the 207pb–206pb ages for sphene do not appear to have been affected.An electroplating technique was employed for recovering the lead from the sphenes after decomposition in perchloric and hydrofluoric acid.

TEM/AEM characterization of fine-grained clay minerals in very-low-grade rocks: Evaluation of contamination by empa involving celadonite family minerals

1996 ◽  
Vol 54 ◽  
pp. 694-695
Author(s):  
Gejing Li ◽  
D. R. Peacor ◽  
D. S. Coombs ◽  
Y. Kawachi
Keyword(s):  
Electron Microscopy ◽  
Volcanic Rocks ◽  
Analytical Electron Microscopy ◽  
Metamorphic Rocks ◽  
New Mineral ◽  
Chemical Compositions ◽  
Low Grade ◽  
Fine Grained ◽  
Depth Analysis ◽  
Mineral Aggregates

Recent advances in transmission electron microscopy (TEM) and analytical electron microscopy (AEM) have led to many new insights into the structural and chemical characteristics of very finegrained, optically homogeneous mineral aggregates in sedimentary and very low-grade metamorphic rocks. Chemical compositions obtained by electron microprobe analysis (EMPA) on such materials have been shown by TEM/AEM to result from beam overlap on contaminant phases on a scale below resolution of EMPA, which in turn can lead to errors in interpretation and determination of formation conditions. Here we present an in-depth analysis of the relation between AEM and EMPA data, which leads also to the definition of new mineral phases, and demonstrate the resolution power of AEM relative to EMPA in investigations of very fine-grained mineral aggregates in sedimentary and very low-grade metamorphic rocks.Celadonite, having end-member composition KMgFe3+Si4O10(OH)2, and with minor substitution of Fe2+ for Mg and Al for Fe3+ on octahedral sites, is a fine-grained mica widespread in volcanic rocks and volcaniclastic sediments which have undergone low-temperature alteration in the oceanic crust and in burial metamorphic sequences.

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