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
|Published (Last):||19 September 2005|
|PDF File Size:||12.92 Mb|
|ePub File Size:||12.51 Mb|
|Price:||Free* [*Free Regsitration Required]|
Chemical analysis of metamorphic rock types. The name diorite is used herein chiefly because of the instrusive nature of the rock and its intermediate composition. Argob de Derechos al uso Exclusivo No. Rock samples from Table 6 plotted on ACF and A’KF diagrams for the quartz-albite-moscovite-chlorite subfacies of the greenschist facies of Barrovian-type regional metamorphism. This unit consists of a very fine-grained 0. Porphyritic diorite sample 53 was crushed and the plagioclase dattacion were removed.
AIl the samples plot near the plagioclase low curve, indicating that the plagioclase is ordered, probably as a result of slow cooling. Petrographic Summary of Igneous Rock Types.
Term Bank – argon – Spanish English Dictionary
Two periods of folding are supported, however, by lenses of marble occurring conformably within the phyllites of Arroyo Talamantes, which show two directions of folding within a single hand specimen.
Rhyolite flows blanket the tops of large mesas south of the city of Zacatecas and overlie the Las Pilas Diorite and the Zacatecas Conglomerate. This very fine-grained calcite may coarsen to blocky, sparry calcite, and veins ofsecondary sparry calcite are abundant. X-ray diffraction patterns were run for all the plagioclase. The quartzite is hard and massive and is similar to the quartzite layers contained in member iii of Unit B but it contains less cIay than the quartzite of the interlayered member.
Silicified rhyolite also crops out northwest of and within the city of Zacatecas in the form of large enlongated dikes which cut the La Pimienta phyllite and the Las Pilas Diorite and typically cap the tops of peakes and ridges. Additional plagioclase was separated by heavy liquid from twelve other powdered dibritc samples whose An content had been previously determined on the universal stage in order to determine their structural states.
It occurs in the groundmass as very fine 0. The true thickness of this unit is impossible to determine since it is the uppermost metasedimentary unit.
The most abundant metamorphic rocks in the field area are phyllites, some of which have slaty or schistose affinites. The Las Satacion Diorite has the charachteristics of a hypabyssal intrusion.
Summary of stratigraphic units defined in the La Pimienta Phyllite. Another important aspect of the structure of this area concerns the rather marked difference in structural complexity between Arroyo Talamantes and Arroyo del Alamo. The rock is characterized by uniform texture and mineralogy, and very fine grain size 0. The cleavage consistently strikes approximately north-south and dips to the east at ootasio angles. Minor chlorite 3 percent and epidote 2 percent also are present.
Relict sedimentary plagioclase feldspars An displaying albitc twinning are abundant as are irregularly shaped masses of iron oxides and hydroxides. The structural state of the plagioclase and the field relations, taken together, strongly suggest an intrusive origin for the diorite Ranson et al.
Other phenocrysts were wrapped in platinum foil and heated in a graphite crucible with an oxygen-acetylene torch, producing a datacio glass. Ranson 1Louis A. Morphotectonic units of Mexico after Dengo, The only sedimentary rock exposed in the region is a red conglomerate composed chiefiy of metamorphic and dioritic rock fragments.
For a more detailed description of the Zacatecas Conglomerate see Edwards op.
Datación Potasio-Argón (K-Ar)
Recognition of the alkali feldspar is potaio because of its close association with plagioclase, and its alteration to sericite. Schweiz, Mineral Petrograph, v.
Pods and lenses of metaconglomerate, which are characteristic of member iii, occur both conformably and in fault contact with the interbedded phyIlite and quartzite. The area of study is part of the Mesa Central morphotectonic province of central Mexico. Both the grayish-purple and the grayish-orange phyIlite possess bedding-plane cleavage and consists of very fine-grained 0.
K–Ar dating – Wikidata
In the case of quartz, porphyroblasts begin to form. Second, the Zacatecas “greenstones” do not appear to be volcanics but, instead, intrusive diorite related to a shallow pluton that intruded the Triassic metasedirnents. Unit D is unique in its appearance and limited extent.
The few structural orientations obtained for bedding-plane cleavage are in accord with the general structural trend of the surrounding units.
The topographic map, which served as a base for the general geologic map of the region, has a scale too small 1: Hematite 1 to 2 percent is less abundant than limonite and occurs as elongated, feathery masses, Iying optasio to planes of foliation.
In Figure 9a stable mineral assemblages, with the addition of quartz and albite, are: The duration of the Laramide orogeny in Mexico is not yet known, but with the start of the Eocene, volcanism became more widespread in northeast and south-central Mexico.
Groundmass plagioclase, accompanied by mafic minerals, fills the interstices between microphenocrysts of pyroxene and plagioclase.
Further study, centered around the chemistry of individual mineral phases, is necessary before the detail of these reactions can be successfully learned. 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.
The concentration of water was determined for selected samples by a modification of the Penfield method Shapiro and Brannock, America Abstracts with Programs, V. Both are present in the groundmass and as small porphyroblasts. Homogeneous, fine-grained, medium-dark-gray, slaty phyllite; contains metaquartzite tenses.
Evidence for this thrusting, cited by de Cserna, comes from the area under investigation in this report. Intrusion of a relatively dry diorite arhon into a sequence of sedirnents undergoing greenschist facies metamorphism would probably result in the production of hot aqueous solution in amounts sufficient to have produced the pervasive autometamorphism of diorite.
In order to better illustrate the textural and mineralogical characteristics of the metamorphic rocks, the detailed datafion of a representative phyllite and marble is presented below.