POR FISIÓN; DATACIÓN POR HELIO; DATACIÓN POR PLOMO ; en el am- biente acuático. datación por potasio-argón Método para determinar la edad. Request PDF on ResearchGate | Cronologia potasio-argón del Complejo Efusivo Copahue-Caviahue, Provincia del Neuquén Potassium-Argon chronology of. d Kalium e potasio potassium-ammonium chloride; potazote () argon d Kalium – Argon Alterbestimmung e datación con potasio – argón
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Evidence for this thrusting, cited by de Cserna, comes from the area under investigation in this report.
The pre-Mesozoic geologic history of Mexico, particularly that of the Precambrian and Early Paleozoic, is poorIy known. Two-point maxima are obtained, suggesting two episodes of foIding. The largest and best exposured outcrop of metaconglomerate appears to be in fault contact with the interbedded quartzite and phyllite.
Rocks of Units C and F contain a fracture cleavage consisting of microscopic fractures which disrupt and offset the primary cleavage. It occurs in the groundmass with plagioclase and as stubby, subhedral to anhedral microphenocrysts. In light of this, this report will concentrate of the Mesozoic vatacion and metamorphic rocks ofthe region. Few geologic studies have been made of the Sierra de Zacatecas in spite of the great argn importance of the area.
The premetamorphic lithologies were limestones and quartzarenites, both of which contained aluminous clays. In as much as the diorite is almost always altered and weathered, classification of this op. In thin section the major phases, quartz and sericite, are accompanied by alkali feldspar, plagioclase, iron oxides and hydroxides, and minor biotite.
It occurs in the groundmass as very fine 0. Epidote 1 percent and clinozoisite 1 percent vatacion accessory minerals in all phyllites, increasing in abundanee in rock 6 in which reclystallization in the coarser portions of the rock appears to be more complete. Thicknesses were estimated with a five foot Jacob staff.
Datación Potasio-Argón (K-Ar)
In northern Oaxaca a granitc-schist-pegmatite complex way also be of Precambrian age. Hypogene mineralization within the metasediment, the diorite, and the intrusive rhyolite appear to have occurred not long after the intrusion of the rhyolite. Finally, there is no substantial evidence that agon Upper Triassic rocks referred to by de Cserna op. The Paleozoic tectonic history is particularly difficuIt to unravel since the data is scanty and has been amassed from locations separated by considerable distances.
Unit D is unique in its appearance and limited extent.
The late Paleozoic age assigned to the lowermost La Pimienta phyllite by Burckhardt op. Reconnaissance work to the south of Zacatecas shows that these flows are also present in this direction.
Midland, West Texas Geol. Bioclasts or even recrystallized bioclasts potasiio to be absent in the foliated and nonfolialed marble. Quartz 50 percent and fine-grained muscovite 35 percent predominate, but relict plagioclase and lithic fragments 10 to 12 percentepidote 1 percentand opaques 2 to 4 percent occur in lesser amounts.
Boletín de la Sociedad Geológica Mexicana
Schweiz, Mineral Petrograph, v. Lenses of marble with exposures ranging in size from a few square meters to approximately 20 m 2 occur conformably within the phyllite of Unit C. Sericitization typically obscures fragment borders and makes primary mineralogy unrecognizable. The thickness of these layers ranges from 1 to 4 cm. A detailed stratigraphic sequence present in the La Pimienta Phyllite is discussed below.
Subordinate amounts of quartz, potaio epidote are also presento The Zacatecas conglomerate is exposed only to the south of the Veta La Cantera where it unconformably overlies the Las Pilas Diorite.
Term Bank – potasio – Spanish English Dictionary
Quartz and sericite compose approximately 50 and 40 percent of the rocks respectiveIy, with minor tale, chIorite, and epidote accounting for the remaining datzcion percent. Further evidence of a shallow intrusive origen for the diorite are its generally massive nature, its phaneritic grain size and the presence of isolated remnants of La Pimienta Phyllite found in and overIying the diorite Barr, op.
Sample 52 is light gray in hand specimen datafion consists primarily of large mm plagioclase phenocrysts. During the Middle Jurassic-Early Cretaceous interval, tectonic activity was limited to the subsidence of northern Mexico, and inundation of northeastern Mexico was completed by the end of the Early Cretaceous. Age and structural relationships indicate xrgon the intrusion of the Las Pilas Diorite was concurrent with the deformation an metamorphism of the La Pimienta Phyllite.
Microscopic examination reveals the presence of quartz and pyrite in addition to calcite. Lithic fragments are large 0. This member is also a very fine-grained 0. This orogeny, which is probably equivalent to a phase of the Nevadan orogeny, appears to correspond well with the first period of deformation and metamorpbism determined by our study of the rocks near Zacatecas. As there is no evidence for an unconformity within the La Pimienta Phyllite, it is believed that the entire sequence is of late Triassic-Jurassic?
Datación potasio-argón (K-Ar)
Also if pyrophyIlite aargon less than ten percent of the rack, it would be difficultto detect by whole-rock X-ray diffraction. Groundmass quartz is usually interspersed with sericite, and grains show slight elongation, with long axes subparallel to the long axes of sericite flakes. Zoltan de Cserna and Fernando Ortega G. Diorite dikes cutting through the quartzite are prevalent. Petrochemistry and petrogenesis Analyses of 16 samples of igneous and metamorphic rock Tables 3 and 4 were performed by X-ray spectrography and atomic absorption spectrometry.
Bibliography Amador, Manuel G.