scholarly journals Rb−Sr and Ar−Ar systematics of Malani volcanic rocks of southwest Rajasthan: Evidence for a younger post-crystallization thermal event

1996 ◽  
Vol 105 (2) ◽  
pp. 131-141 ◽  
Author(s):  
S S Rathore ◽  
T R Venkatesan ◽  
R K Srivastava
Keyword(s):  
Volcanic Rocks ◽  
Thermal Event

Problème de la limite Précambrien–Cambrien: étude radiochronologique par la méthode U–Pb sur zircons du volcan du Jbel Boho (Anti-Atlas marocain)

1977 ◽  
Vol 14 (12) ◽  
pp. 2771-2777 ◽  
Author(s):  
J. Ducrot ◽  
J. R. Lancelot
Keyword(s):  
Volcanic Rocks ◽  
Lower Paleozoic ◽  
Thermal Event

A 534 ± 10 Ma age has been obtained on zircons from Jbel Boho volcano by the U–Pb method; previous assumptions of older ages for the Anti-Atlas Infracambrien (Morocco) cannot be maintained. This formation belongs to the lower Paleozoic. A slight thermal event has affected the volcanic rocks during Variscan (or Hercynian) times and induced opening of the K–Ar and Rb–Sr systems; but the U–Pb system of the zircons has not been affected. These U–Pb data are further reasons to raise the Precambrian – Cambrian boundary to an age of 550–560 Ma.

U–Pb ages of some crystalline rocks from the Burlington Peninsula, Newfoundland, and implications for the age of Fleur de Lys metamorphism

1977 ◽  
Vol 14 (10) ◽  
pp. 2316-2324 ◽  
Author(s):  
James M. Mattinson
Keyword(s):  
Volcanic Rocks ◽  
Primary Crystallization ◽  
Early Carboniferous ◽  
New Age ◽  
Crystalline Rocks ◽  
Thermal Event ◽  
Early Ordovician ◽  
Early Stages ◽  
Intrusive Rocks ◽  
Show Evidence

U–Pb measurements on minerals from the Burlington Peninsula indicate that volcanic rocks of the Grand Cove Group and the probably cogenetic Cape Brule porphyry have primary crystallization ages of 475 ± 10 Ma (Early Ordovician). Later intrusive rocks, including the Dunamagon granite, the Burlington granodiorite and the Seal Island Bight syenite were intruded between 445 and 435 Ma ago. The Grand Cove Group and the Cape Brule porphyry completely predate deformation and metamorphism of the eastern division of the Fleur de Lys Supergroup; the Seal Island Bight syenite, Burlington granodiorite, and Dunamagon granite were evidently emplaced during the early stages of this orogeny. The new age results therefore suggest that the orogeny is Taconic in the classic sense. Some of the isotope systems show evidence of a strong thermal event about 340 Ma ago (Early Carboniferous, Acadian). This event may have caused resetting of some of the Rb–Sr isochron ages recently reported for this area.

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.

Author response for "Sequence and petrogenesis of the volcanic rocks from the middle Sanjiang Tethys Orogen, SW China: Implications for the Sanjiang Paleo‐Tethyan evolution"

2020 ◽  
Author(s):  
Lifei Yang ◽  
Changming Wang ◽  
Bin Du ◽  
Qi Chen ◽  
Zhicheng He ◽  
...  
Keyword(s):  
Volcanic Rocks ◽  
Author Response ◽  
Sw China
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