Gneiss, marbres, prasinites en coussins et polymetamorphisme dans la partie sud-occidentale du massif Dora-Maira (Alpes cottiennes piemontaises)

1961 ◽  
Vol S7-III (4) ◽  
pp. 345-354
Author(s):  
Andre Michard ◽  
P. Vialon
Keyword(s):  
White Mica ◽  
Igneous Rocks ◽  
Metamorphic Rocks ◽  
Retrograde Metamorphism ◽  
Po River ◽  
Alpine Metamorphism

Abstract Igneous rocks of the Dora-Maira massif in the Po river headwater region in the Cottian Alps of Piedmont, Italy, are surrounded, and in many places surmounted, by gneiss, marble, and other associated metamorphic rocks of controversial age. The evidence is considered conclusive that the age of the rocks ranges from Permo-Carboniferous to Triassic. Criteria for discrimination of successive periods of metamorphism, including retrograde metamorphism, are reviewed. Carbonatized rocks and phengitic conglomeratic quartzite serve as "metamorphic thermometers" useful locally for discriminating successive periods of metamorphism. Cataclastic effects are also useful for determining time relationships, as are also optical peculiarities of quartz, feldspar, white mica, and biotite in various rocks. It is concluded that the region has been subjected to two major periods of metamorphism, and that the Alpine metamorphism in general was less intensive, and in certain aspects was retrograde compared with the pre-Alpine metamorphism.

Potassium–Argon Age Determinations of Metamorphic and Plutonic Rocks in the Yukon Crystalline Terrane

1975 ◽  
Vol 12 (11) ◽  
pp. 1895-1909 ◽  
Author(s):  
D. J. Tempelman-Kluit ◽  
R. K. Wanless
Keyword(s):  
Volcanic Rocks ◽  
Igneous Rocks ◽  
Metamorphic Rocks ◽  
Retrograde Metamorphism ◽  
Acid Volcanic ◽  
Quartz Monzonite ◽  
Plutonic Rocks ◽  
Dyke Swarms ◽  
Age Determinations

Forty-four new potassium–argon age determinations on minerals of metamorphic and igneous rocks from the Yukon Crystalline Terrane define the timing of the three most recent thermal events affecting this region. The oldest, 160 to 170 Ma ago, involved weak retrograde metamorphism of igneous and metamorphic rocks and coincides with the intrusion of batholiths of pink quartz monzonite. The next event, 90 to 100 Ma ago, reflects the emplacement of batholiths of the Coffee Creek quartz monzonite suite. The youngest thermal episode, 50 to 60 Ma ago, marks the time when the Nisling Range alaskite, with its porphyry dyke swarms and explosive acid volcanic rocks, was emplaced and when the K–Ar system of the Ruby Range Batholith was thermally reset. The data provide a younger limit to the age of the oldest Mesozoic plutonic rocks, the Klotassin suite, but they do not define its time of emplacement.

40Ar/39Ar age constraints for an early Alpine metamorphism of the Sakar unit, Sakar–Strandzha zone, Bulgaria

2020 ◽  
Vol 157 (12) ◽  
pp. 2106-2112
Author(s):  
Nikolay Bonev ◽  
Richard Spikings ◽  
Robert Moritz
Keyword(s):  
White Mica ◽  
Upper Permian ◽  
Metamorphic Rocks ◽  
Cooling History ◽  
Aegean Region ◽  
Metasedimentary Rocks ◽  
Facies Metamorphism ◽  
History Of ◽  
Alpine Metamorphism ◽  
Age Constraints

AbstractWe investigated the Sakar unit metamorphic rocks of the Sakar–Strandzha zone in Bulgaria, using 40Ar/39Ar dating of amphibole from the polymetamorphic basement and white mica in the overlying upper Permian metasedimentary rocks of the Paleokastro Formation. The amphibole and white mica revealed plateau ages of 140.50 ± 1.75 Ma and 126.19 ± 1.29 Ma, respectively, indicating an Early Cretaceous cooling history of the regional amphibolite-facies metamorphism to greenschist-facies conditions. Similar metamorphic grades and cooling histories of the Sakar unit share evidence with the nearby Rhodope Massif for the northern Aegean region-wide early Alpine tectonometamorphic event.

Revised stratigraphy of the Mesozoic rocks of southern Cyprus

1980 ◽  
Vol 117 (6) ◽  
pp. 547-563 ◽  
Author(s):  
R. E. Swarbrick ◽  
A. H. F. Robertson
Keyword(s):  
Oceanic Crust ◽  
Continental Margin ◽  
Late Cretaceous ◽  
Sedimentary Cover ◽  
Igneous Rocks ◽  
Late Triassic ◽  
Metamorphic Rocks ◽  
Southern Cyprus

SummaryRecent resurgence of interest in the Mesozoic rocks of SW and southern Cyprus necessitates redefinition of the Mesozoic sedimentary and igneous rocks in line with modern stratigraphical convention. Two fundamentally different rocks associations are present, the Troodos Complex, not redefined, a portion of late Cretaceous oceanic crust, and the Mamonia Complex, the tectonically dismembered remnants of a Mesozoic continental margin. Based on earlier work, the Mamonia Complex is divided into two groups, each subdivided into a number of subsidiary formations and members. The Ayios Photios Group is wholly sedimentary, and records the evolution of a late Triassic to Cretaceous inactive continental margin. The Dhiarizos Group represents Triassic alkalic volcanism and sedimentation adjacent to a continental margin. Several other formations not included in the two groups comprise sedimentary mélange and metamorphic rocks. The Troodos Complex possesses an in situ late Cretaceous sedimentary cover which includes two formations of ferromanganiferous pelagic sediments, radiolarites and volcaniclastic sandstones. The overlying Cainozoic calcareous units are not redefined here.

Evidences of talc-white mica assemblage in low-grade metamorphic rocks from the internal zone of the Rif Cordillera (N Morocco)

2020 ◽  
Vol 195 ◽  
pp. 105723
Author(s):  
Mª. Dolores Rodríguez-Ruiz ◽  
Isabel Abad ◽  
María Bentabol ◽  
Mª. Dolores Ruiz Cruz
Keyword(s):  
White Mica ◽  
Metamorphic Rocks ◽  
Low Grade ◽  
Internal Zone

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.

scholarly journals APATITE-ALBITE METASOMATITES (ACEITES) OF THE EASTERN ALDAN-STANOVOY SHIELD

2021 ◽  
Vol 40 (5) ◽  
pp. 59-73
Author(s):  
V.E. Kirillov ◽  
Keyword(s):  
Rare Earth ◽  
Structural Control ◽  
Earth Element ◽  
Rare Metal ◽  
Igneous Rocks ◽  
Metamorphic Rocks ◽  
Intrusive Rocks ◽  
Characteristic Features ◽  
Metasomatic Zoning ◽  
Geochemical Specialization

The paper summarizes the findings of research on Riphean ore-bearing apatite-albite metasomatites (aceites) identified in metamorphic, volcanic and intrusive rocks in the eastern Aldan-Stanovoy shield. The characteristic features of lithological and structural control of aceites, their mineral and petrochemical composition, geochemical associations, ontogeny, metasomatic zoning, and geochemical specialization are outlined. Aceites in metamorphic rocks are assigned to the albite-chlorite-apatite facies and in igneous rocks to the albite-apatite facies. Apatite-albite metasomatites host mineralization of two types: uranium (in aceites after metamorphic rocks) and uranium – rare earth element – rare metal (in aceites after volcanic and intrusive rocks).

scholarly journals Pétrographie characterization of rocks from the Mirabello bay region, Crete, and its application to Minoan archaeology: the provenance of stone implements from Minoan sites

2007 ◽  
Vol 40 (4) ◽  
pp. 1768 ◽  
Author(s):  
H. M. Dierckx ◽  
B. Tsikouras
Keyword(s):  
Raw Materials ◽  
Igneous Rocks ◽  
Metamorphic Rocks ◽  
Rock Samples ◽  
Rock Types ◽  
Source Regions ◽  
Time Period

The Minoans of East Crete used a variety of igneous and metamorphic rocks as stone implements. These were probably procured in dry riverbeds and beaches located in a region along the Bay of Mirabello or from an onlap conglomerate, which geologically dominates that region and contains rock types of igneous, metamorphic and sedimentary origin. Several rock samples were collected for pétrographie investigation to examine and confirm the source for the igneous rocks. Detailed pétrographie description of natural samples provides the identification of the rocks employed by Minoans and confirms the source of their origin. Apparently the Minoans were able to evaluate the hardness of the stones procured according to the desirable usage and their expected fatigue, thus avoiding unnecessary timeconsuming treatment. The identification of the variable lithotypes used for these implements and the verification of their source regions reveal the time it took to procure the raw materials as well as the time period during which the rocks were employed.

scholarly journals Rock Types Classification and Distribution on Anabanua Village, Barru Regency, South Sulawesi

2020 ◽  
Vol 8 (1) ◽  
pp. 1-8
Author(s):  
Muhammad Resky Ariansyah ◽  
Muhammad Fawzy Ismullah Massinai ◽  
Muhammad Altin Massinai
Keyword(s):  
Sedimentary Rocks ◽  
Research Area ◽  
Igneous Rocks ◽  
The Other ◽  
Metamorphic Rocks ◽  
Geological Process ◽  
Rock Types ◽  
South Sulawesi ◽  
Geological Conditions ◽  
Limestone Sand

Anabanua Village, Barru Regency is one of the areas in South Sulawesi that has quite unique geological conditions. This condition inseparably comes from the complicated geological process that took place during the formation of the island, Sulawesi. In Anabanua Village, there are many types of rocks such as sedimentary rocks, metamorphic rocks and igneous rocks. This paper aims to map and classify the types of rock by taking samples on different places in the research area. Then we observe the samples physical properties. The results showed, from taking 10 rock samples in different places, they have various characteristics. 8 of them were sedimentary rocks, they are Limestone Quartz, Limestone Sand, Shale, Sandstone, Coal, Limestone Bioturbation, Breccia, and Chert Stone. The other 2 samples were metamorphic rocks, they are Greenschist and Quartzite.

scholarly journals Chemical Analyses of Igneous and Metamorphic Rocks of Denmark, the Faeroes and Greenland. (To and including 1940)

1942 ◽  
Vol 68 ◽  
pp. 1-105
Author(s):  
Sole Munck ◽  
Arne Noe-Nygaard
Keyword(s):  
Comparative Study ◽  
Igneous Rocks ◽  
Geological Survey ◽  
Metamorphic Rocks ◽  
Chemical Analyses ◽  
The Past ◽  
De Quervain ◽  
Set Up ◽  
The Comparative Study

The past ten years or so have seen the publication of collections of chemical rock analyses which, as a result of their clear form of set-up, in many ways faciliate the comparative study of the chemistry of the rocks and their mutual relationships. Among these publications there are: P. Niggli, F. De Quervain & R. U. Wintherthalter: Chemismus schweizerischer Gesteine. Bern 1930, and the analyses publish ed by the Geological Survey of Great Brita in: Chemical Analyses of Igneous Rocks, Metamorphic Rocks and Minerals. London 1931. Similar publications are available from two neighbouring countries, i.e. from Sweden: W. Larsson: Chemical Analyses of Swedish Rocks (Bull. Geol. Inst., Uppsala 1932) and from Finland : L. Lokka: Neuere Chemische Analysen von Finnisch en Gesteinen (Bull. Comm. Geol. de Finlande No. 105. Helsingfors 1934).

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