Neotethyan Late Cretaceous volcanic arc hydrothermal vent fauna

Abstract

The barite-polymetallic ore zone of the Late Cretaceous Madneuli volcanogenic massive sulfi de (VMS) deposit in the Republic of Georgia contains large tube worm fossils that represent the fi rst ancient hydrothermal vent fauna to be identifi ed from a volcanic arc setting and very likely the shallowest ancient example yet found. The fossil tube walls are formed of an unusual quartz, barite, pyrite, and galena mineral assemblage, rather than only pyrite as in other vent fossils; this probably refl ects the low-temperature, high-salinity vent chemistry at the time of preservation, as deduced from fl uid inclusion analyses. The Madneuli vent fauna is one of three examples that occurred over a time span of ~6 m.y. in an area of the Neotethyan Ocean that was as tectonically complex as the present-day west Pacifi c. The ancient and modern vent faunas appear to occur in a similar range of tectonic settings and bathymetry.

Mineralization of Alvinella polychaete tubes at hydrothermal vents

“…Worm tube fossils with diverse morphologies are known from vent sites in the geological record back to the early Silurian period,~430 million years ago (Little et al, 1998(Little et al, , 1999(Little et al, , 2004(Little et al, , 2007Hil ario et al, 2011), but little is known about the animals that formed them. Although some have been assigned to extant vent polychaete groups, morphological identifications are not generally consistent with estimates of molecular divergence (Little & Vrijenhoek, 2003;Vrijenhoek, 2013) and there is potential confusion with morphologically similar polychaete tubes (Kiel & Dando, 2009).…”

Review of Late Cretaceous volcanogenic massive sulfide mineralization in the Eastern Pontides, NE Turkey

“…Tube worm fossils are also characteristic of seafloor sulfide accumulations (e.g., Haymon, 1983;Qudin and Constantinou, 1984;Jonasson and Perfit, 1999;Doyle and Allen, 2003) and are evidence of Paleo seafloor hydrothermal vents in the Pontides (Revan et al, 2014). These tubular worm-like fossils can be considered ancestral forms of the unusual vent communities on the modern seafloor (Haymon et al, 1984;Banks, 1986) and have been assigned by several researchers (Kuznetsov and Sobetskii, 1988;Maslennikov, 1991;Little et al, 1997Little et al, , 2007Shpanskaya et al, 1999;Revan et al, 2010Revan et al, , 2014 to tube worms based on the following criteria: 1) similar geoecological conditions, 2) consistent associations with chimney fragments in massive orebodies, and 3) similarity to other ancient examples in the Urals, Cyprus, Oman, and Georgia in terms of their shapes and partially their sizes and contents.…”

Late Cretaceous hydrothermal vent communities from the Troodos ophiolite, Cyprus: systematics and evolutionary significance

“…1985; Boirat & Fouquet 1986; Little et al . 1997, 1998, 1999 a , b , c , 2007; Revan et al . 2014; Georgieva et al .…”

“…From the Madneuli VMS of Georgia are three smooth‐walled tubes that are considerably larger than any of the Cypriot tubular fossils, being between 6.8 and 11.9 mm in diameter (Little et al . 2007). The Lahanos and Killik VMS of Turkey contain tubular fossil‐like structures that are even larger than the Madneuli tubes, being 20–25 mm in diameter (based on Revan et al .…”