Shoshonitic Association Research Articles

Archean cratonization, emergence and red bed development, Lake Shebandowan area, Canada

The Archean sequence of Lake Shebandowan area consists of Keewatin group rocks, overlain with probable unconformity by volcanic and sedimentary rocks of the “Timiskaming’ The Keewatin volcanic rocks are predominantly pillowed metabasalts chemically analogous to modern island arc tholeiites. The Timiskaming consists of calc-alkaline volcanic rocks and alluvial-fluvial rudites and arenites. The Timiskaming volcanic rocks are hornblende and feldspar phyric basalt to rhyolite. Deposits are massive unsorted volcanic breccias and rare graded tuff-breccias. The fragments are calc-alkaline and include a high-K shoshonite association, and, thus, are analogous to calc-alkaline suites of mature island arcs. The Timiskaming sedimentary rocks represent immature detritus from proximal Timiskaming volcanic centres. They were deposited in an alluvial-fluvial environment as evidenced by mudcracks, debris flow, sheet flood and traction deposits. Localized hematitte pigmentation in the Timiskaming strata is interpreted as evidence of red bed development. The Fe 2O 3/FeO ratio is higher in rocks pigmented by hematite than in equivalent samples without pigmentation. This increase in the oxidation state of iron is probably the result of emergence and interaction of Timiskaming strata with interstitial oxidizing fluids analogous to those of contemporary red beds. The transition from Keewatin tholeiitic pillow basalts to an unconformably overlying Timiskaming calc-alkaline volcanic suite suggests progressive cratonization accompanying stratigraphic build-up. The presence of a high-K shoshonite association in Timiskaming volcanic rocks implies that orogeny, crustal thickening and stabilization of a Keewatin basaltic platform occurred prior to Timiskaming volcanism. The eventual emergence and erosion of a landmass led to deposition of alluvial-fluvial sedimentary facies in which red beds subsequently developed.

The subalkaline potassic magmatism of the Ballons massif (Southern Vosges, France): shoshonitic affinity

A systematic geochemical study of the Ballons plutonic complex (Southern Vosges, France) indicates that the border facies of the massif are composed of two continuous differentiation series ranging from gabbros to quartz monzonites and very similar to the shoshonitic associations (high K 2O/Na 2O ratios as well as high Ba, Sr, U and Th contents). The existence of a geochemical discontinuity between the two series and the monzogranite, which is the principal component of the massif, argues against the monzogranite being directly related to the two differentiation series by fractional crystallization. The zoned structure of the monzogranite can be attributed to in situ crystal fractionation.

Geotectonic settings of miocene-quaternary volcanism in and around the eastern Tyrrhenian sea border (Italy) as deduced from major element geochemistry

The volcanic rocks along the south-eastern and eastern Tyrrhenian border of Italy have been classified as converging plate margin magma types by using discriminant functions based on major element patterns. These rocks belong to calc-alkaline and shoshonitic associations (shoshonites, and predominant leucitic rocks) ranging in age from Upper Miocene to, mostly, Quaternary.

Calc-alkaline and shoshonitic lavas from five Andean volcanoes (between latitudes 21° 45′ and 24°30′S) and the distribution of the Plio-Quaternary volcanism of the south-central and southern Andes

The Plio-Quaternary volcanic rocks of the south-central Andes (southward from latitude 18°S) contain two associations: calc-alkaline and shoshonitic which coincide with seismic belts as geographically distinct zones aligned parallel to the oceanic trench. There is a continuous gradation from calc-alkaline to shoshonitic associations. The shoshonitic association appears to the north of latitude 26°S; southwards, the calc-alkaline association directly abuts against the continental (Argentinian) alkaline association. Thirty-one lavas from the Plio-Quaternary calc-alkaline Socompa, Lascar, Sairecabur and Tocorpuri and shoshonitic Sierra de Lipez volcanoes were studied. The lavas are porphyric with abundant glass. The distribution and the nature of the phenocrysts vary according to the chemistry of the calc-alkaline lavas. Petrographic evidence for crystal fractionation has been observed. Occasional phenocrysts of alkali feldspars occur in the shoshonitic lavas. The K 2O and SiO 2 contents increase from calc-alkaline to shoshonitic lavas with distance away from the oceanic trench. In lavas from Socompa, Lascar, Sairecabur and Tocorpuri calc-alkaline volcanoes, K 2O, Li and Rb increase and K/Rb and Sr decrease with increasing SiO 2; Ba increases with decreasing Sr, probably as a result of plagioclase fractionation. In lavas from Sierra de Lípez shoshonitic volcano, SiO 2 is high, K 2O is high and rather constant and Li, Rb, Ba and Sr increase with increasing SiO 2. Bolivian shoshonitic lavas appear to be genetically related to the calc-alkaline suite. The calc-alkaline lavas may be derived by crystal fractionation from a parental magma of andesitic nature that originated in or above the subjacent Benioff zone.

Criticism of generalised models for the magmatic evolution of arc-trench systems

Recent geological and petrological results from the Lesser Antilles island arc and Papua New Guinea, and from other regions of arc-trench-type volcanism, provide notable exceptions to the spatial, volumetric, and temporal relationships claimed for generalised arc models. For example, many alkalic and shoshonitic associations do not appear to be developed over the deepest parts of downgoing slabs, and there are now several well-documented exceptions to the K 2O/SiO 2/depth-to-Benioff-zone relationship. Moreover, the temporal sequence of early tholeiitic → middle calcalkalic → late shoshonitic/alkalic is not well substantiated, although shoshonitic rocks do appear to be developed most commonly in regions with a long history of plate interactions. Exceptions to the generalised arc model are symptomatic of the need to look for the unique features of individual island arcs, rather than just similarities between different ones, so that the major factors controlling arc evolution may be determined.

The volcanic rocks from the Mount Agnello area (Fiemme Valley, Italy): A contribution to the knowledge of the mid-Triassic magmatism of the Southern Alps

Middle Triassic volcanic rock outcrops in the Mount Agnello area (Fiemme Valley, Italy) are examined in this study. Chemical analyses based on main and trace elements (Rb, Sr, Zr, Y, Nb) allow this volcanism to be defined as “shoshonitic”. The amphiboles, which occur with thick opacitic rims, were determined as ferroan pargasites. They were often found in volcanites of calcalkaline and/or shoshonitic associations. Consequently, this volcanism can be associated with a newly orogenized area undergoing stabilization. These data support the more recent studies on the mid-Triassic volcanism in the Southern Alps and underline the particular position of this magmatism in the tectonic evolution of this area.

Comments on “Evolution of Eolian arc volcanism (Southern Tyrrhenian Sea)” by F. Barberi, G. Ferrara, F. Innocenti, J. Keller and L. Villari

Sr-isotopic measurements were performed on samples of each main stage of eruption of the various Eolian islands, coupled with REE and Rb, Sr, U, Th, Hf and Sc determinations. A subcrustal origin is invoked for the older calc-alkaline series related to the subduction zone of the Eolian arc confirming the view of Barberi et al. (1974). A different explanation is given for the shoshonitic association which shows higher 87Sr/ 86Sr values and different REE concentrations, making a direct derivation from the mantle doubtful. Contamination by crustal material or anatexis of the lower crust are considered as possible mechanisms. Finally the significance of a shoshonitic series is questionned.

Petrology of some volcanic rock series of the Aeolian arc, Southern Tyrrhenian Sea: Calc-alkaline and shoshonitic associations

In the Aeolian island arc two different magmatological associations, calc-alkaline andesite series and shoshonites, occur in close vicinity. Although both associations erupted simultaneously during the last glaciation, there is a general tendency for the calc-alkaline rocks to be older. Shoshonitic activity is still going on.

The shoshonitic association in the upper Mesozoic of Tasmania

Abstract During the Late Mesozoic, igneous activity in Tasmania produced a number of small intrusive bodies and swarms of dykes. Typical examples of these rocks are found on the West Coast and around Cape Portland and Cygnet. The rocks belong to a shoshonitic association and they form part of a more extensive petrographic province that extends from Tasmania into eastern Australia. It is proposed that the magmas from which these rocks were derived evolved at depth beneath the stabilised western margin of the New Zealand Geosyncline. The composition of this magma which formed in a relatively stable environment, contrasts with the more basic magma that erupted during the period of crustal tension that accompanied the break up of the Australian segment of Gondwanaland during the past 200 m.y.

Some chemical data on members of the shoshonite association

Summary A number of minerals and residual glasses from absarokites, shoshonites, and latites have been analysed by electron probe. Clinopyroxenes show very little iron-enrichment and these rocks are thus distinguished from tholeiites and alkali basalts. Glasses from this group are also distinct from tholeiites and alkali basalts and occupy a separate field on a CaO-Na2O-K2O diagram.

Late Cainozoic Shoshonitic Lavas from Torres Strait, Papua and Queensland

JOPLIN1,2 has proposed the term shoshonite association to describe certain potash-rich lavas and intrusive rocks known from various parts of the world. These rocks are as alkalic as those of the soda-rich alkali-olivine basalt association, but their K2O : Na2O ratio is near or greater than 1.0 compared with 0.5 for the alkali basalts; magnesium and calcium are higher for equivalent SiO2 values and there is less total-iron and TiO2. In the South-west Pacific region shoshonitic rocks have recently been recognized in Fiji3, in eastern Papua4 and in the Highlands of New Guinea5. During a regional survey in far northern Queensland in 1968, basic rocks with similar shoshonitic tendencies were encountered on several small volcanic islands in Torres Strait, between the Papuan coastline and the Australian mainland.

High potassium calc-alkaline rocks from Cape Nelson, eastern Papua

High-K calc-alkaline rocks from Cape Nelson, eastern Papua are dominated by andesites containing numerous basic inclusions. High-Al basalts and dacites are subordinate. The slight iron enrichment and a systematic variation in K2O/SiO2 correlation observed in these rocks suggests a relationship to nearby rocks of a shoshonite association. The chemical composition of the inclusions illustrates the trends of major and minor element evolution which contradict the idea of complimentariness of high-K calc-alkaline rocks and alpine ultramafic rocks. The chemical character of the lavas (high K, Rb and Ba as well as high Cr and Ni) can be explained by fractional melting involving a mica phase.

The shoshonite association: A review

Abstract The absarokite‐shoshonite‐banakite series described from Yellowstone Park by Iddings and the ciminite‐toscanite series described from western Italy by Washington are compared. In both regions these rocks are associated with leucite‐bearing rocks, potassium‐rich trachytes and with andesitic rocks with above average potassium. A similar association of rock‐types is described from Indonesia and several other regions including the Rift Valley of Africa where, at Bufumbira, Holmes & Harwood have described members of the absarokite‐shoshonite‐banakite, potassium trachytes and leucite rocks. It is concluded that the absarokite‐shoshonite‐banakite series and the ciminite‐toscanite series are parts of a single rock association here called the shoshonite association. Intrusive members, such as monzonites, are also briefly discussed. The relation of the shoshonite association to the tholeiite, alkali basalt, calcal‐kaline and carbonatite associations are examined and an attempt is made to relate these to te...

Italian Petrological Sketches.: III. The Bracciano, Cerveteri and Tolfa Regions

Previous articleNext article FreeItalian Petrological Sketches.: III. The Bracciano, Cerveteri and Tolfa RegionsHenry S. WashingtonHenry S. Washington Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The Journal of Geology Volume 5, Number 1Jan. - Feb., 1897 Article DOIhttps://doi.org/10.1086/607701 Views: 76Total views on this site Citations: 4Citations are reported from Crossref PDF download Crossref reports the following articles citing this article:Davis Young Origin of the American Qantitative Igneous Rock Classification: Part 2, Earth Sciences History 28, no.22 (Nov 2009): 175–203.https://doi.org/10.17704/eshi.28.2.334n7uk31v1060g7Charlotte Clausen, Paul Martin Holm Origin of the acidic volcanics of the Tolfa district, Tuscan Province, central Italy: an elemental and Sr-isotopic study, Contributions to Mineralogy and Petrology 105, no.44 (Sep 1990): 403–411.https://doi.org/10.1007/BF00286828Germaine A. Joplin, E. Kiss, N. G. Ware, Jennifer R. Widdowson Some chemical data on members of the shoshonite association, Mineralogical Magazine 38, no.300300 (Jul 2018): 936–945.https://doi.org/10.1180/minmag.1972.038.300.04Germaine A. Joplin The shoshonite association: A review, Journal of the Geological Society of Australia 15, no.22 (Jan 1968): 275–294.https://doi.org/10.1080/00167616808728699

Absarokite-Shoshonite-Banakite Series

Absarokite-Shoshonite-Banakite Series