El origen del salitre de Chile

• Autores: B. Fiestas Contreras
• Localización: Boletín de la Real Sociedad Española de Historia Natural. Actas, ISSN 0583-7499, Nº. 64, 1966, págs. 46-56
• Idioma: español
• Texto completo no disponible (Saber más ...)
• Resumen
  • English

    Saltpetre exploted in Chilean deserts and most of the salts existing in the pampas or deserts of the Peruvian coast, have the same origin. In Peru, as in Chile, the nitrates exist with other salts, chloride, sulfate, etc.

    The genesis of all these salts has been owing to the action of acidic emanations over the rocks in situ where we find now the deposits.

    The eruption of acidic clouds propagated along the Pacific coast that forms the salt deposits, took place in the counter forts of the Andes near Arequipa, at 2.500 m. over sea level, from a fissure of 35 Km. in the slopes of Chachani Mount.

    The effusion gave rise to the Arequipa Formation(sillar,Kaolin, salts).

    The Arequipa Formation is the most recent one known in the region and it could coexist with a glacial formation. There are evident marks of previous and later glaciations, specially later, not being strange that the eruption could occur during a period of intense glaciation.

    The dominating salts are chlorides and sulfates. Nitrates keep the same quantitative relation with borates. The actual difference is that borates remain in the rocks as insoluble salts of boronatrocalcite while nitrates were washed by rains, or where it existed vegetation, have disappeared.

    The zone of maximun concentration of salts is near the eruptive focus, south Arequipa in the pampas of Huagri, Cachendo, PampaRosadaand Clemensi desert.

    The sulfates are more concentrated near the place of eruption.

    The acids acting on the rocks left free the sand or silica and kaolin with re-mains of unattacked rock. Where the action was intense, a conglomerate was formed resembling the riolites that constitute thesillar.

    Coastal winds have exerted influence in the distribution of acids, consequently to the relation in which they are in the saltt.

    Beside the cinerite, white kaolin also existed forming a great part of the deposits, being observed easily on the mountains around Arequipa reaching 100 Km. to the southwest. This white mantle, like snow, marks the acids rute when someone is flying.

    Nitrates quantity existting in the flat basing in insufficient to initiate acomercialexplotation by the techniques known up to date. A good concentration was verified in Chile in gently slopes of places non affected- by rains. II was also found in the same way commercial saltpetre in some plans ofPerú,although in less proportion.

    The eruptive whitesillarof Arequipa is the final product as a result of the silicic acid attack and other mineral acids on the andesite that spreads very widely.

    Jointly to the Arequipa formation, whitesillar,rosesillarand kaolin exist, hat we could name, the intrusive primarysillar,determinated in the right side of Caplina River, Tacna. The beds position of this intrusivesillaris inverse to effusivesillar.

    Deposits of sodic, potassic and caleic carbonates existing in small basins at the higher parts of the Andes Belt, can be attributed to the combined action of sulfuric and nitric acids over the vegetation when the eruption was produced.

    The acids influence reached along he coast 2.000 Km. northward and the the same distance southward, from the eruption place.

    Salts concentration in the deposits is inversely proportional to the distance of the eruptive center, so in the northern limit corresponding to Sechura desert, the total thickness of salts was indicated to be 10 cm. while in Arequipa was more than 1 m., increasing to 1,50 m. southward, to decrease again disappearing to the final end of Chilean deposits, thant is in Copiapo, south Talcal.

    The region between the coastal provincees ofPerúand Chile with salt deposits, constitute a petrographical province of maximun oxidation incompatible with oil existence. The salisphare zone reaches 2.500 m. high over sea level.

  • français

    On fait l'étude des formations salines de la zone a coté de l'Ocean Pacific et leurs limites en Perú et Chile.

    On afirme l'origin unique des sels qui ont été formées in situ par l'action des emanations acides sur les terrains.

    On traite de fixe lesconditions par les quelles les nitrates ont été concentrés pour former les gisements du salitre.

    On dit que la pluie des acidesa été correlative á l'erupcion de la riolite qui forme le sillar en Arequipa.