We have carried out zircon U-Pb SHRIMP dating and Hf isotope determinations as well as geochemical analyses on three plutonic units of Gondwanan magmatism that crop out in NW Argentina. Two episodes of different age and genesis have been identified. The older one includes gabbros and diorites (Río Grande Unit) of 267±3 Ma and granitoids (belonging to the Llullaillaco Unit) of 263±1 Ma (late Permian, Guadalupian); the parent magmas were generated in an intraplate environment and derived from an enriched mantle but were subsequently contaminated by crustal components. The younger rocks are granodiorites with arc signature (Chuculaqui Unit) and an age of 247±2 Ma (middle Triassic-Anisian). Hf isotope signature of the units indicates mantle sources as well as crustal components. Hf model ages obtained are consistent with the presence of crustal Mesoproterozoic (mainly Ectasian to Calymnian (T DM(c)=1.24 to 1.44 Ga-negative εHf m) and juvenile Cryogenian sources (T DM=0.65 to 0.79 Ga-positive eHf (T)), supporting the idea of a continuous, mostly Mesoproterozoic, basement under the Central Andes, as an extension of the Arequipa-Antofalla massif. The tectonic setting and age of the Gondwanan magmatism in NW Argentina allow to differentiate: a. Permian intra-plate magmatism developed under similar conditions to the upper section of the Choiyoi magmatism exposed in the Frontal Cordillera and San Rafael Block, Argentina; b. Triassic magmatism belonging to a poorly known subduction-related magmatic arc segment of mostly NS trend with evidence of porphyry type mineralization in Chile, allowing to extend this metallotect into Argentina.

Se presentan resultados de la geoquímica, dataciones U-Pb SHRIMP y de relaciones isotópicas Lu-Hf de tres unidades plutónicas pertenecientes al magmatismo gondwánico del NW de Argentina. Se identificaron dos episodios de diferente edad y génesis. El más antiguo incluye gabros y dioritas (Unidad Río Grande) de edad 267±3 Ma y granitoides (pertenecientes a la Unidad Llullaillaco) de 263±1 Ma (Pérmico tardío-Guadalupiense) generados en un ambiente de intraplaca a partir de un manto enriquecido y subsecuentemente contaminado con componentes corticales. El evento más joven está representado por la intrusión de granodioritas (Unidad Chuculaqui) de 247±1 Ma (Triásico medio-Anisiense) con características químicas de arco magmático. El comportamiento de los isótopos de Hf de las unidades estudiadas indica la participación de fuentes mantélicas como así también de componentes corticales en su generación. Las edades modelo Hf obtenidas son consistentes con la presencia de fuentes corticales del Mesoproterozoico (principalmente Ectasiano a Calimniano (1,24 a 1,44 Ga-εHf negativo) y juveniles del Criogeniano (T DM=0,65 to 0,79 Ga-εHf m positivo), lo que está de acuerdo con la presencia de un basamento continuo, de ese rango de edades, bajo los Andes Centrales, como una extensión del macizo de Arequipa-Antofalla. El ambiente tectónico y la edad del magmatismo gondwánico en el NW de Argentina permiten diferenciar: a. Un magmatismo pérmico de intraplaca desarrollado bajo condiciones similares a las del magmatismo carbonífero de intraplaca descrito para Cordillera Frontal y Bloque de San Rafael; b. Un magmatismo triásico perteneciente a un segmento de arco magmático de orientación predominante NS con evidencias de mineralización tipo pórfiro en Chile, lo que permite extender este metalotecto en el territorio argentino.

This paper reviews the historical development of a two-dimensional (direction x distance (?)) neural model of defense. It begins with Miller's (1944) analysis, and model, of approach, avoidance and conflict; adds Hinde's (1966) ethological perspective and Flynn's (1967) neural model of fear; and then considers Gray's (1967, 1970) work linking barbiturate action to the hippocampus, McNaughton's (1977) extension of this to other classes of anxiolytics, and Gray & McNaughton's (1983) detailed behavioral comparison of anxiolytics and hippocampal lesions. This work led to Gray's (1982) detailed model of the neuropsychology of anxiety. Rapoport's (1989) model of the control of obsession by the cingulate cortex, and Ledoux's (1994) model of the control of both fear and anxiety to the amygdala, suggested a more complex organisation of defense systems. McNaughton (1989) argued that evolutionary function defines an emotion, and Blanchard and Blanchard (1990) argued for its assessment via ethoexperimental analysis. Graeff (1994) then produced a neural model that mapped defensive distance to neural level, treating all anxiety as being at a greater defensive distance than fear. Seeing this, and the treatment of anxiety as due to uncertainty (which is inconsistent with Miller's data), as being unsatisfactory, Gray and McNaughton (2000) and then McNaughton and Corr (2004) developed the two-dimensional model of defensive systems. This model is clearly incomplete at the present time and its links with neuroeconomics, personality, and stress and greater specification of frontal cortical contributions are suggested as directions for future development.