geoscience.net logo
+ Resolve Article
+ Follow Us
Follow on FacebookFollow on Facebook
Follow on TwitterFollow on Twitter

+ Translate
+ Subscribe to Site Feed
GeoScience Most Shared ContentMost Shared Content

An Early Cretaceous volcanic arc/ marginal basin transition zone, Peninsula Hardy, southernmost Chile


, : An Early Cretaceous volcanic arc/ marginal basin transition zone, Peninsula Hardy, southernmost Chile. Journal of Volcanology and Geothermal Research 63(1-2): 33-58

The Hardy Formation represents a latest Jurassic-Early Cretaceous volcanic arc that was located along the Pacific margin of southern South America. It was separated from the continent by a marginal basin floored by portions of an ophiolite sequence (the Rocas Verdes ophiolites). The transition between the arc and marginal basin occurs on Peninsula Hardy, southernmost Chile, where there is a lateral facies transition from arc deposits of the Hardy Formation into proximal marginal basin fill of the Yahgan Formation. Interfingering of arc and marginal basin sequences demonstrates that subduction-related arc magmatism was concurrent with marginal basin formation. The lateral facies transition is reflected in the geochemistry of volcanic rocks from the Hardy and Yahgan formations. Basalts, andesites and dacites of the arc sequence follow a calc-alkaline differentiation trend whereas basalts from the marginal basin follow a tholeiitic differentiation trend. Estimates of temperature and oxygen fugacity for crystallization of the arc andesites are similar to values reported for other calc-alkaline andesites. It is suggested that water activity influenced the early or late crystallization of Ti-magnetite and this controlled the style of differentiation of the magmas erupted on Peninsula Hardy. Magmas with high water contents evolved along the calc-alkaline differentiation trend whereas those with low water contents evolved along the tholeiitic differentiation trend. Some rhyolites are differentiated from the calc-alkaline andesites and dacites, but most appear to be the products of crustal anatexis on the basis of trace-element evidence. The arc basalts and some marginal basin basalts show relative enrichment in LILE, relative depletion in HFSE, and enrichment in LREE. Other marginal basin basalts are LREE depleted and show small relative depletions in HFSE. Basalts with both calc-alkaline and tholeiitic affinities can also be recognized in the Rocas Verdes ophiolites, where their eruption is correlated with temporal changes in the evolution of the marginal basin. Geochemical data are consistent with derivation of all basalts from a mantle source that is a mixture of MORB-like mantle and variable proportions of a subduction-related component. Basalts with calc-alkaline affinities were erupted initially in the marginal basin, when the locus of back-arc magmatism was near the active arc and the upper mantle source region was strongly influenced by components released from the subducted slab. MORB-like tholeiitic basalts were erupted at a later stage in the wider parts of the basin, when the angle of subduction had increased, the trench had rolled back, and the basin had widened. These MORB-like tholeiitic magmas reflect partial melting of mantle dominated by upwelling asthenosphere containing only a minor component, if any, derived from the subducted slab.

US$19.90

DOI: 10.1016/0377-0273(94)90017-5


Other references

Peris, SJ.; Martin, A.; Velasco, JC., 1994: Age, growth and reproduction of the cyprinid Tropidophoxinellus alburnoides Stephanidis, 1974 in river Agueda, west-central Spain. Age, growth and reproduction of the T. alburnoides population of the River Agueda, Duero basin are analysed. Females dominated all age classes and lived up to 6 years (5+) while males only reached 4 years (3+). The growing season extended from Mar...

Takamatsu, S.; Rho, M.-Chual; Masuma, R.; Hayashi, M.; Komiyama, K.; Tanaka, H.; Omura, S., 1994: A novel testosterone 5-alpha-reductase inhibitor, 8',9'-dehydroascochlorine produced by Verticillium sp. FO-2787. A new testosterone 5-alpha-reductase inhibitor, 8',9'-dehydroascochlorin, was isolated from the cultured mycelium of Verticillium sp. FO-2787. This compound (M.W.: 402, C-23H-27ClO-4) consists of 5-chloroorcylic aldehyde and 2,3,4-trimet...

Uzan, M.; Favre, R.; Brody, E., 1988: A nuclease that cuts specifically in the ribosome binding site of some T4 mRNAs. We have identified a nucleolytic activity in Escherichia coli infected by bacteriophage T4 that introduces cuts in the ribosome binding site of at least two T4 mRNAs. Cutting takes place specifically in the GGAG sequences that are complementary to...

Bolden Watson, C.; Watson, M.; Richelson, E., 1993: Effect of the neurotensin receptor antagonist SR48692 on the expression of neurotensin and neurotensin receptor mRNA in rat brain. Society for Neuroscience Abstracts 19(1-3): 1184

Shaffer, T.E., 1963: Misconceptions In Athletics And Physical Education. Journal of School Health 33: 346-350

Van Gerpen, J.A.; Wider, C.; Broderick, D.F.; Dickson, D.W.; Brown, L.A.; Wszolek, Z.K., 2008: Insights into the dynamics of hereditary diffuse leukoencephalopathy with axonal spheroids. To report a new American family with hereditary diffuse leukoencephalopathy with spheroids (HDLS), including serial, presymptomatic and symptomatic, cranial MRIs from the proband. We report clinical and genealogic investigations of an HDLS family,...

Murphy, J.W.; McDaniel, D.O., 1982: In vitro reactivity of natural killer (NK) cells against Cryptococcus neoformans. The level of NK reactivity of the effector cell pools (unstimulated murine nylon wool-nonadherent splenic cells) using a 4 h 51Cr-release assay with YAC-1 targets correlated with the ability of effector cells to limit the growth of C. neoformans....

Serajuddoula M.; Banik R.L., 1988: Vegetative propagation of bamboos through branch cutting. Vegetative propagation of three commerically important species of bamboos, Bambusa vulgaris Schard, Bambusa polymorpha Munro and Melocanna baccifera Trin was carried out through branch cuttings in a semi-controlled temperature and humidity propaga...

García Jalón, E.Guiomar.; Lennon, S.; Peoples, L.; Murphy, S.; Lowe-Strong, A., 2013: Energy conservation for fatigue management in multiple sclerosis: a pilot randomized controlled trial. To develop and test the feasibility of an energy conservation programme to manage fatigue in multiple sclerosis.>A pilot randomized controlled trial.>Community setting.>People with multiple sclerosis reporting fatigue.>An energy conser...

Althoff, C.E.; Hermann, K.G.; Braun, J.; Sieper, J., 2006: Ankylosierende Spondylitis. Aktueller Stand der bildgebenden Verfahren einschlieBlich Scoring-Methoden. Conventional radiography and magnetic resonance imaging (MRI) are currently the most widely used imaging methods for the initial diagnostic evaluation and follow-up of patients with ankylosing spondylitis (AS). Scintigraphy, computed tomography (...