Carbon sedimentary

In the northern part of the TCZ, the Chaleurs Group comprises subaerially deposited. Late Silurian bimodal volcanic rocks that overlie early Silurian shallow marine fine- to coarse-grained clastic and carbonate sedimentary rocks. The Chaleurs Group is overlain disconformably by bimodal volcanic rocks and interlayered sandstones and siltstones of the Dalhousie Group. 

A major change was also occurring during this period in the field of carbonate sedimentary petrology where there was an increasing awareness of the need to apply more sophisticated approaches to the study and interpretation of... 

Button (1976) considers the BIF of the Transvaal Supergroup, South Africa, to be the final member of a carbonate sedimentary cycle, when anomalous concentrations of iron, silica, and other elements were produced in restricted basins. 

Button, A., 1976. Iron-formation as an end member in carbonate sedimentary cycles in the Transvaal supergroup. South Africa. Econ. Geol, 71 193-201. 

The input fluxes of various volatile species (Table 10) can now be compared to various output fluxes through arc volcanism (Table 9) to assess the extent of volatile mass balance. At this stage, we ignore possible volatile losses at the back-arc given the large uncertainty in actual values. Also, we note that in the case of subducted carbon, it is important to distinguish between reduced sedimentary carbon, sedimentary carbonate and carbonate of the altered oceanic crust. 

Carbonated sedimentary rocks Limestones, dolomites, and marl Evaporitic sedimendary rocks Rock salt, gypsum, and anhydrite Phosphatic sedimentary rocks Phosphates, phophorites... 

The abrupt changes in depositional environments, styles and tectonic setting of Middle and Late Proterozoic rocks and their associated uranium deposits are significant evidence of extensive changes in supracrustal processes. Calc-alkaline volcanic and ophiolitic oceanic crustal suites are lacking in strata of this age. " Rock sequences are dominated by shallow marine to fluvial arenaceous clastic and carbonate sedimentary strata, and subaerial tholeiitic basalt and related shallow intrusions, all deposited in passively subsiding, rift-controlled basins. Oro-... 

Carbonate sedimentary rocks are dominantly of marine origin. Many limestones are composed of fossilised shell debris in various states of comminution, some fine grained carbonates such as chalk (q.v.) may be entirely composed of sub-microscopic phytoplankton. Algal mats secrete aragonite particles and coral reefs are CeiCO structures which may be preserved, fossilised, intact or degraded to produce other limestones. As discussed above, allochems such as faecal pellets and ooliths may be... 

Oil reservoirs are layers of porous sandstone or carbonate rock, usually sedimentary. Impermeable rock layers, usually shales, and faults trap the oil in the reservoir. The oil exists in microscopic pores in rock. Various gases and water also occupy rock pores and are often in contact with the oil. These pores are intercoimected with a compHcated network of microscopic flow channels. The weight of ovedaying rock layers places these duids under pressure. When a well penetrates the rock formation, this pressure drives the duids into the wellbore. The dow channel size, wettabiUty of dow channel rock surfaces, oil viscosity, and other properties of the cmde oil determine the rate of this primary oil production. 

The commercial grades of calcium carbonate from natural sources are either calcite, aragonite, or sedimentary chalk. In most precipitated grades aragonite is the predominant crystal stmcture. The essential properties of the two common crystal stmctures are shown in Table 1. 

Sedimentary rocks (like sandstone) have a microstructure rather like that of a vitreous ceramic. Sandstone is made of particles of silica, bonded together either by more silica or by calcium carbonate (CaCOj). Like pottery, it is porous. The difference lies in the way the bonding phase formed it is precipitated from solution in ground water, rather than formed by melting. 

Oil and gas are usually associated with sedimentary rocks. The three basic types of sedimentaiy rocks are shales, sands, and carbonates. The shales are the sources of the hydrocarbons while the sands and carbonates act as the conduits and/or the containers. 

Limestone. This is a sedimentary rock that is formed by the accumulation of organic marine life remains (shells or coral). Its main component is calcium carbonate. Cement rock. This is a sedimentary rock that has a similar composition as the industrially produced cement. 

The amounts of the standard isotopic species and the tracer isotopic species are represented by X and X for the sample and the reference material. The reference substance is chosen arbitrarily, but is a substance that is homogeneous, available in reasonably large amounts, and measurable using standard analytical techniques for measuring isotopes (generally mass spectrometry). For instance, a sample of ocean water known as Standard Mean Ocean Water (SMOW) is used as a reference for and 0. Calcium carbonate from the Peedee sedimentary formation in North Carolina, USA (PDB) is used for C. More information about using carbon isotopes is presented in Chapter 11. 

Schidlowski, M. (1988). A 3 800 million year isotopic record of life from carbon in sedimentary rocks. Nature 333,313-318. 

Of the possible substituting ions, COi ion is by far the most important followed by Na, S04 and Mg. The most common form of natural apatite in sedimentary rocks is francolite, a substituted form of carbonate fluorapatite deposited in marine systems. The substitution of col ior>s into the mineral lattice has a substantial effect on apatite solubility (Jahnke, 1984). More studies are required, however, before the effects of all substituting ions are imderstood and an accurate assessment of the solubility of complex, natural apatites can be made. 

---