Características composicionales del Complejo Volcánico Sur I de Fuerteventura (Islas Canarias)

The Southern Volcanic Complex I consists mainly of basalts with scarce felsic members. On the basis of chemical and mineralogical compositional features two groups could be considered. 80th groups are alkaline, the first normal alkaline (in the Cofete Area) and the second one more alkaline (in the Mungía Area). When the proportions of crystallizing phases are estimated, these two groups show different behaviour. The first group is controlled by olivine and c1ynopiroxene and the second one by these two phases plus plagioclase and magnetite. These two different evolution paths culminate with also two different more differentiated members. The basic rocks in the Cofete Area are related to the trachytes of Montaña Azufrá whilst these in the Mungía Area are connected to the felsic rocks of Cofete Islet

Edad de los domos sálicos de la isla de La Gomera

The new radiometric data from felsic domes on La Gomera allow to separate two different felsic both intrusive and extrusive episodes on the island. The early one, upper Miocene in age, includes the domes on the eastern sector of the island as well as the radial and the conical dikes cropping out on the north. Within this early episode of felsic magmatism, the domes on the eastern sector and the so called eastern radial dike-swarm seem to be contemporaneous and slightly older (8.6-7.9 Ma) than the western radialdike swarm and the con e-sheet complex, a structure which also includes some related domes (7.5-6.4 Ma). A later felsic episode, lower Pliocene in age (4.5-3.9 Ma),includes all the rest of existent domes on La Gomera which are less alkaline and peralkaline than the older ones

Edificios volcánicos en la Serie I de Fuerteventura: Rasgos generales del edificio central

The Old Basaltic Series in Fuerteventura is formed by three main edifices: Northern, Central and Southern (or jandíaJ Edifices. The Central Edifice, a shield volcano, extends from El jable towards Valles Ortega area forming a semicircular shape around a large adjacet basin. The edifice is built up by dipping outwards thick basaltic flows piles in which pyroclastic are scarce. Three different subseries, can be distinguished within these piles: Lower, Medium and Upper Series, all separated by unconformities. A fourth active episode, the Late Series, filled the inner basin, and was clearly emitted after a large tectonic graben took place

Serie Basáltica Antigua Inferior en el sector de Hermigua. Isla de la Gomera

Lower Old Basaltic Series had only been described W of the Basal Complex in Alojera-Tazo area but it is also well exposed in other zones on Gomera as in Hermigua area E of the Basal Complex. Here, the basaltic lava flows alternate with poligenetic agglomerates. The lowermost lavas show some submarine features. Their chemicaI a ffin ity is mildly a Ikaline and their age is about 9-7 O M.y

Características generales del Edificio Norte de la Serie I de Fuerteventura

The North Edifice is one of the three main edifices identified in the Old Basaltic Series of Fuerteventura. This edifice is formed by Lower, Intermedium and Upper Series. The oldest one crops out on the low western side of the structure where the materials - thick basaltic lava flows- are densely crossed by a complex dyking and are normally fractured, showing a clastic appearence. The Intermedium Series is formed by a thick (up to 750m) agglomerate with some interlayered basaltic lava flows. The Upper Series constitued an incomplete shield volcano now separated in long and high "cuchillos". The younger two series show a simple radial trend of dykes pointing to an area situated east of Los Molinos

El edificio sur (Jandía) de la serie I de Fuerteventura: rasgos generales

The Jandia is one of the three main edifices identified in the Old Basaltic Series of Fuerteventura. It shows now a semicircular shape with a nortwards facing opening. This large volcano built up by lava flows and pyroclastics corresponding to three successive subseries: Lower, Medium and Upper Series all separated by unconformities. The jandia Lower Series is probably equivalent to the Lower Series which has been identified in the Central Edifice farther to the north-east. A fourth period of activity (Late Series) which formed a low table land, took place west of the present semicircular edifice

Edad de los diques sálicos del Norte de la isla de La Gomera

Several trachytic and phanalitic, radial and canical dyke-swarms crap out an the La Gomera narthern regian. The first age data abtained situate the intrusian episades coinciding in time with the extrusian af the Old Basalts. The earlier dykes shaw a radial pattern, centred in Tamargada. They have been dated in 8.0 Ma and 7.9 Ma. The canical swarm centred farther west, in Vallehermasa, has a slightly more recent age, between 7.5 Ma and 6.4 Ma. A third dyke-swarm is spatially assaciated with the canical structure and has likely a similar age

Características composicionales y procesos de evolución magmática en el Complejo Volcánico Central (I y II) de Fuerteventura (Islas Canarias)

The Central Vólcanic Complex I (CVC-I) consists maihly of mildly alkaline basalts, many of them ankaramitic. The compositional differences observed are explained by fractíonation and extraction (rates between 20% and 30%) of clinopyroxene (60%), olivine (20-25%) and titanomagnetite. The CVC-II shows two different stages. The lower one of mildly alkaline affiníty has an age comprised between 20 and 22 Ma, the more alkalic: upper orle has a mote recent age about 18Ma. The crystallization models for the lower stage are different depending on the composition considered to be the most primary or less differentiated magma. The crystallization rates are comprised between 20 and 30%. The compositional variation observed in the basalts from the upper stage may be due to crystallization rates from 20-25%, mainly olivine (50c70%) and clinopyroxene. The transition to trachyandesites, both in the CVC-I and the CVC-II¡ supposes a change in crystallization which is then dominated by cilinopyroxene and plagioclase. The further transition to trachytes is a process controlled by plagioclase extraction