Formation of modern and Paleozoic stratiform barite at cold methane seeps on continental margins

Abstract

Stratiform (bedded) Paleozoic barite occurs as large conformable beds within organicand chert-rich sediments; the beds lack major sulfide minerals and are the largest and most economically significant barite deposits in the geologic record. Existing models for the origin of bedded barite fail to explain all their characteristics: the deposits display properties consistent with an exhalative origin involving fluid ascent to the seafloor, but they lack appreciable polymetallic sulfide minerals and the corresponding strontium isotopic composition to support a hydrothermal vent source. A new mechanism of barite formation, along structurally controlled sites of cold fluid seepage in continental margins, involves barite remobilization in organic-rich, highly reducing sediments, transport of barium-rich fluids, and barite precipitation at cold methane seeps. The lithologic and depositional framework of Paleozoic and cold seep barite, as well as morphological, textural, and chemical characteristics of the deposits, and associations with chemosymbiotic fauna, all support a cold seep origin for stratiform Paleozoic barite. This understanding is highly relevant to paleoceanographic and paleotectonic studies, as well as to economic geology. Figure 1. A: Locations of cold seep barite deposits. B: Barite columns (3 m high) on seafloor at sites of fluid seepage along San Clemente fault.

Laser Raman spectroscopy as a technique for identification of seafloor hydrothermal and cold seep minerals

“…Naehr, et al (2000) hypothesized that the site was the result of a sediment slump exposing barium-rich pore waters to sulfate-rich seawater. This site is similar to other cold-seep barite sites observed along continental margins (Torres et al, 2003) (e.g., at the San Clemente Fault (Lonsdale, 1979) and in the Sea of Okhotsk (Greinert et al, 2002)). …”

Geochemical characteristics of the barite deposits at cold seeps from the northern Gulf of Mexico continental slope

“…The distinct characteristics of the seep-related barites makes it possible to identify their ancient analogs, such as the studies performed by Torres et al (2003) and Johnson et al (2009). Based on a comparison with δ 34 S versus δ 18 O patterns of modern seep-related barite, Johnson et al (2009) argued that several of the Paleozoic barite deposits are seeprelated although many of these deposits are carbonate-free.…”

“…These observations indicate that barite deposition might be an important process along many continental margins and may have affected the global marine barium cycle in the geological past (e.g. Castellini et al, 2006;Dickens, 2001;Dickens et al, 2003;McQuay et al, 2008;Snyder et al, 2007;Torres et al, 1996aTorres et al, ,b, 2002Torres et al, , 2003.…”

Geochemistry and Fuid-Inclusion Microthermometry of the Farsesh Barite Deposit, Iran

“…9A). Therefore, the occurrence of hydrothermal barite in the Frasesh deposits points at low to intermediate temperatures (150-250°C), at the sea bottom near hydrothermal plumes (Hein et al, 2007), where they were accompanied by minor amounts of base-metal sulphides (Torres et al, 2003). As shown in Figure 9B, there is a non-similarity between the REE distributions of the Farsesh barite deposit and the REE patterns of marine barite (Guichard et al, 1979).…”