Turbidite

For example, the many deepwater fields located in the Gulf of Mexico are of Tertiary age and are comprised of complex sand bodies which were deposited in a deepwater turbidite sequence. The BP Prudhoe Bay sandstone reservoir in Alaska is of Triassic/ Cretaceous age and was deposited by a large shallow water fluvial-alluvial fan delta system. The Saudi Arabian Ghawar limestone reservoir is of Jurassic age and was deposited in a warm, shallow marine sea. Although these reservoirs were deposited in very different depositional environments they all contain producible accumulations of hydrocarbons, though the fraction of recoverable oil varies. In fact, these three fields are some of the largest in the world, containing over 12 billion barrels of oil each ... 

Fig. 2.49. Map of pre-Neogene tectonic division of northern Japan and locations of the Shimokawa and the Hitachi mines. 1 Abukuma Belt, 2 South Kitakami Belt, 2h Hayachine Structural Belt, 3 North Kitakami Belt, 4 Iwaizumi Belt, 5 Taro Belt, 6 Ishikari Belt, 7 Kamuikotan Belt, 8 Hidaka Belt (a Hidaka Western Greenstone Belt, b Greenstone-Chert-Turbidite Facies Belt, c Hidaka Metamorphic Belt, d Turbidite Facies Belt), 9 Tokoro Belt, 10 Nemuro Belt (Mariko and Kato, 1994).

In the control area, Lombador, the phosphorus, an essential element in plants nutrition, presents, in the relationsoil-plant, a different behavior from the other areas. This can be related to the substratum rock in the Lombador area which is composed of metassediments (turbidites) and are not included in Volcano Sedimentary Complex as the other areas where mining works have occurred. 

The first modem publication of Li isotope data from sediments came from Chan et al. (1994a), who reported the isotopic compositions of unaltered turbidites from DSDP Hole 477 and All A, from the Gulf of California. These samples have been reanalyzed (LH Chan, written communication 2003), yielding lighter values. Similarly, Chan and Frey (2003) suggested a range for marine clastic sediments (5 Li = -1 to +5.6) based on new data and re-analysis of samples previously considered to be isotopicaUy heavy. 

Sediments ranging from clay-rich to carbonate-rich from ODP Sites 1039 and 1040, outboard of Costa Rica, had variable isotopic compositions, unrelated to their bulk chemistry (5 Li = +9.5 to +23.3 Chan and Kastner 2000). Turbidites and underlying ash-rich mudstones at ODP Site 808, southwest of Japan, defined a similarly large range in isotopic compositions (5 Li = -1 to +8 You et al. 1995). James et al. (1999) reported 8 Li for variably altered sandy to silty turbidites to hemipelagic muds from ODP Site 1038, off the coast of northern California (-0.5 to +5.6). 

James et al. (2003) performed laboratory experiments in which aqueous fluids were reacted with natural samples of unaltered MORE (5 Li = +4.6) and a quartzofeldspathic mud/turbidite mixture (5 Li = +1.3). The starting fluids had elemental compositions generally intermediate between seawater and hydrothermal fluids, and were isotopically light (5 Li = -5.5). The initial fluid/solid was 4. Fluid samples were extracted as the experiments were raised to 350°C over 400-500 h, and then during cooling (c. 740 h total). In both experiments Li was removed from solution at low temperatures, but the isotopic composition of the fluids... 

Clastic sediments from oxic environments (loess, turbidites, grey shales) 1 ... 

Many turbidites found on the continental margins are characterized by graded bedding 13.8). This type of particle sorting is produced by the sequential deposition... 

Since these sediments contain only clay- and silt-sized particles, the graded bedding in these deposits is not as pronounced as in the nearshore turbidites. 

Turbidite The sedimentary deposit created by turbidity currents. The latter are underwater mudslides common to the continental slope and rise. 

Turbidity current An underwater mudslide common to the continental slope. The particles deposit at the foot of the slope to form the continental rise. The resulting deposit is often referred to as a turbidite. 

Ramsay, W.R.H., Bierlein, F., Parne, D.C., Vanderberg, A.H.M. 1998. A review of turbidite-hosted gold deposits, central Victoria. Regional setting, styles of mineralisation and genetic constraints. Ore Geology Reviews, 13, 131-151. 

Country rocks in the Cantung mine area consist of rocks typical of the Selwyn Basin, including turbiditic sandstone, deepwater limestone, chert, shale, and dolostone. Two ore-bearing calcareous units of the Sekwi Formation are bound by argillaceous rocks. In mine terminology, the Swiss Cheese Limestone (SCL) is a calcareous siltstone with chert nodules. The Ore Limestone (OL) conformably overlies the SCL, and is a pure, coarsely crystalline marble up to 50m thick. 

Floyd, P.A. Leveridge, B.E. 1987. Tectonic environment of the Devonian Gramscatho basin, south Cornwaii framework mode and geochemicai evidence from turbiditic sandstones. Journal of the Geological Society of London, 144, 531-542. 

The Elura deposit (45 Mt (g 8.5% Zn, 5.3% Pb, 69 ppm Ag) is located 43 km north-northwest of Cobar in western New South Wales (Lorrigan 2005). The deposit is hosted by weakly metamorphosed and deformed turbiditic sedimentary rocks of the Early Devonian Cobar Basin. It consists of a series of vertical, pipe-like sulfide concentrations composed of varying proportions of pyrrhotite, pyrite, sphalerite, galena and accessory sulfide... 

This study has shown that there are important differences in the alteration effects observed in the fine and coarse fractions of the host turbidite units. It is critical to examine and analyse these end members separately as many of the key lithogeochemical features of the alteration would be obscured in bulk samples. 

The Late Cretaceous Pebble deposit is located within the southern part of the Late Jurassic to Early Cretaceous Kahiltna terrane, which is bounded to the southeast by the Peninsular terrane (Late Triassic to Late Jurassic) and to the northwest by flysch of the Kuskokwim Group (middle to Late Cretaceous) (Fig. 1). The southern Kahiltna terrane consists predominately of Jurassic to Cretaceous turbidite deposits and can be divided into two major lithologic units the Koksetna River sequence and the Chilikadrotna Greenstone (Wallace etal. 1989). The... 

LOVELL (J.P.B.), 1969. Tyle formation undeformed turbidites and their lateral equivalents mineralogy and paleogeography. Bull. Geol. 

The probable absence of any pre-Martinsburg carbon concentrations precludes a clastic origin for the nodules. In any case, they are found in the uniform gray slate (originally mud), which was precipitated in the deep, still basin very slowly and are not associated with the clastic debris of the turbidite sequences. Turbulent conditions would have been needed for transport of such pebbles into the environment. 

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