Silicate diagenesis in deep-sea sediments from the Tonga forearc (SW Pacific): a strontium and Rare Earth Elements signature

Abstract

87 Sr/ 86 Sr isotopic ratios, strontium and Rare Earth Element concentrations obtained on volcano-sedimentary rocks and separated clay mineral and zeolite fractions reveal a formation by pore water-volcanic rock interaction for most of the hydrous silicate minerals of the Site 841 ODP collected from the Tonga forearc. Unusual strontium concentrations and isotopic ratios recorded in the Miocene tuffs associated with specific REE patterns indicate that the formation of these hydrous silicates does not follow a simple burial diagenesis model, but was related to the cooling of intruding basaltic sills in the Miocene volcano-sedimentary series. Migration of strontium into the pore water in response to the heat flow induced the formation of Sr-bearing zeolites such as clinoptilolite, heulandite and chabazite. No evidence of any influence of a further thermal pulse in the Eocene rhyolitic tuffs could be found. As recorded by the chemistry of their clay mineral fraction, the rhyolitic tuffs developed a polyphasic diagenetic process, which might have been influenced by a possible circulation of a fluid into structurally weak areas. © 2000 Ifremer/CNRS/IRD/É ditions scientifiques et médicales Elsevier SAS Tonga / silicates / strontium / Rare Earth Elements / diagenesis / heat flow Résumé-Diagenèse des silicates des séries sédimentaires de l'avant-arc Tonga (Pacifique sud-ouest) : étude de la signature en strontium et en terres rares. Les concentrations en strontium et en terres rares, ainsi que les rapports isotopiques 87 Sr/ 86 Sr des roches volcano-sédimentaires et des fractions argileuses et zéolitiques indiquent que la plupart des silicates hydratés du site 841 ODP de l'avant-arc Tonga se sont formés par interaction entre les roches volcaniques et les eaux interstitielles. Les concentrations et rapports isotopiques en strontium inhabituels, enregistrés dans les tufs du Miocène associés à des profils de terres rares spécifiques, indiquent que la formation de ces silicates hydratés ne suit pas un modèle de simple diagenèse d'enfouissement Elle est en relation directe avec le refroidissement d'intrusions de sill basaltiques dans les séries volcano-sédimentaires du Miocène. La migration du strontium dans les fluides interstitiels, en réponse au flux de chaleur, a entrainé la formation de zéolites contenant du strontium, telles que les clinoptilolite, heulandite et chabazite. Dans les tufs rhyolitiques de l'É ocène, aucune influence d'un flux thermique n'a été détectée. La chimie de la fraction argileuse de ces tufs indique qu'ils ont subi une diagenèse polyphasée probablement influencée par la circulation d'un fluide à travers leurs failles.

Nd–Sr isotope and REY geochemistry of metalliferous sediments in a low-temperature off-axis hydrothermal environment (Costa Rica margin)

“…For Sr isotopes, such intermediate compositions in deep-sea sediments are commonly explained by the coexistence of volcanoclastic material with authigenic clays and zeolites (Hoffert et al, 1978;Petzing and Chester, 1979;Lee and Lee, 1998;Vitali et al, 2000). In previous studies it has been shown that authigenesis of clays and zeolites is a result of the interaction of volcanic particles with seawater at the sediment-water interface, and with pore water during early diagenesis (Hay, 1964;Hoffert et al, 1978;Desprairies and Bonnot-Courtois, 1980;Migidisov et al, 1981;Sheppard and Fitzpatrick, 1989;Vitali et al, 2000). The REY patterns of such sediments are similar to those of the reference sediments of the Ticoflux site.…”

Chemical Characteristics for Hydrothermal Alteration of Surface Sediments from Submarine Volcanoes of the Tonga Arc

“…통가열도 지역 해저화산의 표층 퇴적물 내 원소 조성은 다른 열수분출 지역인 동태평양 해령 및 대 서양 중앙해령과 서로 차이를 보인다 (Bender et al, 1971;Bertine, 1974;Hodkinson and Cronan, 1991;Krasnov et al, 1995;German et al, 1999;Daessle et al, 2000;Paropkari et al, 2010 지역에 따라서 차이를 보인다 (Bertine, 1974;Cronan et al, 1986;Hawkins and Helu, 1986;Hodkinson and Cronan, 1991;Bryan et al, 2004 * Some elements were measured below the detection limit due to the dilution rates. (Mooby et al, 1984;Daessle et al, 2000;Paropkari et al, 2010;Cho et al, 2011 (Moorby et al, 1984;Hodkinson and Cronan, 1991;Daessle et al, 2000;Vitali et al, 2000). (Hodkinson and Cronan, 1991;Fouquet et al, 1993;Daessle et al, 2000).…”