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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Microscopic examination reveals the presence of quartz and pyrite in addition to calcite.

Diorites displaying this subtle foliation and concordant contacts, have previously been interpreted as “greenstone lavas which are penecontemporaneous with sediments” Burckhardt and Scalia, op. Evidence for this thrusting, cited by de Cserna, comes from the area under investigation in this report. The close association in time of the metamorphism and the intrusion suggests that the temperatures necessary for greenschist facies metamorphism were attained at shallow depths in the crust.

Datación Potasio-Argón (K-Ar)

In places the diorite intrudes the La Pimienta Phyllite whereas in other areas, paticularly to the north and east of the field area, it overlies the metasediments. Groundmass quartz is usually interspersed with sericite, and grains show slight elongation, with long axes subparallel to the long axes of sericite flakes. Alkali feldspar is present in most ofthe diorites, but in amounts less than 10 percent.

Lithic fragments occur in phyllites which have been incompletely recrystallized.

Método Potasio – Argón by on Prezi

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.

GeneralIy porphyritic, these rhyolite flows contain phenocrysts of quartz, sanidine, and biotite set in a mesostasis of glass or its devitrification products. For reasons of simplicity and clarity, the stratigraphic units which were recognized in the La Pimienta Phyllite are designated by letters rather than names. Groundmass plagioclase, accompanied by mafic minerals, fills the interstices between microphenocrysts of pyroxene and plagioclase.


Chemical and petrographic features of the metamorphic rocks indicate that a relatively dry system may not have allowed relic sedimentary minerals to enter into metamorphic reactions, thus resulting argom disequilibrium assemblages. McGehee in his study of the La Pimienta metamorphics has also failed to find evidence of a major unconformity. Further study, centered around datacon chemistry of individual mineral phases, is necessary before the detail of these reactions can potaeio successfully learned.

Fine-grained calcite forms a mosaic texture that composes the matrix in which the larger grains reside. Other phenocrysts were wrapped in platinum foil and heated in a graphite crucible with an oxygen-acetylene torch, producing a plagioclase argoj.

Petrographic data, reported in a subsequent section of this paper also suggest two periods of folding for this region. Photomicrograph of hydrothermally deuterically altered diorite sample No. Both minerals are fine grained and occur with sericite. Bioclasts or even recrystallized bioclasts appear to be absent in the foliated and nonfolialed marble. In addition, exposures of this metaconglomerate are smaller and more prevalent.

Stable mineral assemblages in Figure 9a include: In hand specimen angular quartz grains are set in a fine-grained 0. Adjacent to the contact, Ienses of diorite less than 1 m in length occur concordantly within the phyllite. Magmatism continued into the Late Tertiary with the extrusion of rhyolite flows, tuffs, and volcanic breccias. Rock samples from Table 6 plotted on the AFM projection plane.

Term Bank – argon – Spanish English Dictionary

The Paleozoic tectonic history is particularly difficuIt to unravel since the data datcaion scanty and has been amassed from locations separated by considerable distances. The contortion and weathering make accurate structural measurements difficult lo obtain, but generally the foliation strikes north-south with moderately steep dips to the east and to the west.


Since that time potazio names andesite, diabase, gabbro, and spilite have been applied. Since there is no contact metamorphism associated with the diorite sill, it is reasonably certain that the ages for the phyllite represent the actual time of metamorphism, rather than the time of argon loss due to the heat produced by the intrusive. Relict minerals and textures suggests that some minerals did not react completely during metamorphisrn.

Reconnaissance work to the agon of Zacatecas shows that these flows are also present in this direction.

Two-point maxima are obtained, suggesting two episodes of foIding. Most of the folding encountered in Arroyo Talamantes occurs in units C and D. Examination of the thin section reveals that some parts of the slide exhibit intergranular texture, with chlorite, fibrous amphiboles, and rarely pyroxene filling the interstices between plagioclase laths Figure 7.

The quartzite lacks obvious follation, but exhibits a crystalloblatic texture and is very hard.

Prior to the late ‘s, published works consisted mainIy of reconnaissance studies dealing with the entire State of Zacatecas, with only brief mention being made of the region in the vicinity of the city of Zacatecas Burkart, ; Amador, ; Burckhardt, ; Flores ; Bastin, In Figure 9a stable mineral assemblages, with the addition of quartz and albite, are: Since the dagacion are much more extensive south of this area and are the focus of another study Brown, op.