Origin of fluids and related barite deposits at vent sites along the Peru convergent margin

Abstract

The venting at the northern Peru convergent margin, unlike at other margins, has produced large barite deposits, which have not been observed outside the vents. The 87 Srf6Sr isotopic ratios of the fluids are more radiogenic than seawater. To explain these elevated values, we propose either the influence of a fluid characterized by a more radiogenic signature originating from the continent, or a reaction between seawater and the underlying continental metamorphic basement. The presence of this nonlocal radiogenic component is marked more strongly on the 87 Sr/" 6 Sr ratios measured in the barite deposits. We assume that the fluid sampled at the venting site and the fluid responsible for the barite deposit sampled at the same site originated from the same source, i.e., the Paleozoic metamorphic basement of the Andean continental margin.

The effect of dissolved barium on biogeochemical processes at cold seeps

“…In this case, barium comes in contact with bottom waters and barite precipitates above the sediment-water interface. Barite chimneys ascribed to this process have been described from the San Clemente Basin (Torres et al, 2002), the Peru Margin (Dia et al, 1993;Aquilina et al, 1997;Torres et al, 1996a), the Monterey Canyon (Naehr et al, 2000), the Gulf of Mexico (Fu et al, 1994) and the Sea of Okhotsk (Greinert et al, 2002). Although the conceptual model proposed by Torres et al (1996a) and Aquilina et al (1997) likely provides a correct qualitative description of this complex diagenetic system, a quantitative understanding of the biogeochemical processes involved is lacking.…”

Slope instabilities at an active continental margin: large-scale polyphase submarine slides along the northern Peruvian margin, between 5 °S and 6 °S

“…are associated with the two species of Calyptogena (01~ et al, 1994a,b). Geochemical analysis of the fluids inside these barite concretions suggest an interaction with the Paleozoic basement (Dia et al, 1993). On several locations of the margin, the Paleozoic outcrops reveal E-W and N-S trending fault system: Along the Bayovar and Amotapes massifs on the coastal plain, onshore Paita and along the Chiclayo canyon (Sosson et al, 1994), to the south, offshore Paita (Fig.…”

“…The westernmost scarp (trench scarp: TS), however, shows a linear trend. This scarp was named subduction scarp (SS) by Dia et al (1993), and marks the boundary between the Nazca and the South American plates ( . .…”

Geochemical Evidence of Continental Fluid Circulation in the Peru Subduction Zone

“…The fluid samples are characterized by common chemical features wherever they are coming from: elevation of the chloride and the Ba contents as well as the S7Sr/a6Sr ratios as compared to seawater local references and IAPSO seawater standard (Dia et al, 1993). We suggest that the deep fluids recovered off northern Peru originated from a mixing between a basinal brine and meteoric waters which circulated in the metamorphic basement.…”