Sedimentary processes

As in the case of igneous processes, the sedimentary processes of rock formation lead to the formation economic mineral deposits. Many valuable mineral deposits of iron, manganese, copper, phosphorus, sulfur, zirconium, the rare Earths, uranium and vanadium owe their origin to sedimentary processes. Some of these constitute special types of sedimentary rocks, while others form important constituents of sedimentary rocks. 

Sanchez JA, Coloma P, Perez A (1999) Sedimentary processes related to the groundwater flows from the Mesozoic Carbonate Aquifer of the Iberian Chain in the Tertiary Ebro Basin, northeast Spain. Sediment Geol 129 201-213... 

These studies introduce and utilize a natural biogeochemical tracer of sedimentary processes. The use of 210Pb to trace deep ocean currents where flocculent material is transported in one region and deposited in another may provide valuable information on deep sea transport. However, more work is required to verify these initial findings. Additional work also is needed to evaluate mechanisms responsible for the differences in diffusion of certain elements in sediments compared to lead and to identify if two types of biological mixing may indeed be responsible for the high sedimentation rates found in the deep ocean. 

The radionuclides which are commonly used for determining the chronology of deep-sea sedimentary processes are given in Table 1. The principal pathways of introduction of these nuclides into the... 

Table 1. Common Chronometers of Deep-Sea Sedimentary Process. ...

Once the radionuclides reach the sediments they are subject to several processes, prime among them being sedimentation, mixing, radioactive decay and production, and chemical diagenesis. This makes the distribution profiles of radionuclides observed in the sediment column a residuum of these multiple processes, rather than a reflection of their delivery pattern to the ocean floor. Therefore, the application of these nuclides as chrono-metric tracers of sedimentary processes requires a knowledge of the processes affecting their distribution and their relationship with time. Mathematical models describing some of these processes and their effects on the radionuclide profiles have been reviewed recently [8,9,10] and hence are not discussed in detail here. However, for the sake of completeness they are presented briefly below. 

The advent of new techniques to collect undisturbed sediment cores, with well preserved sediment - water interface has brought into sharper focus the various deep sea sedimentary processes, their rates and their effects on the preserved records. As mentioned earlier, recent studies have shown that the record contained in sediments is not a direct reflection of the delivery pattern of a substance to the ocean floor as has so far been assumed the record is modified as a result of several complex physical, chemical and biological processes. Therefore, information on the temporal variations in the tracer input to oceans, if sought, has to be deciphered from the sediment-residuum. In the following we consider one specific example of retrieval of information from the sediment pile the application of deep sea sediments to obtain historical records of cosmic ray intensity variations. 

Most of the heavy metal contaminants associated with mining or agricultural practices are released from less common mineral phases, some of which are primary (i.e., formed initially by an igneous, metamorphic, or sedimentary process) and some of which are secondary (i.e., formed by chemical alteration of the primary minerals). Table 7.4 lists some of the more common contaminant ions and the mineral phases with which they are associated in economic mineral deposits or weathered zones associated with these deposits. 

McLennan, S.M. (1989) Rare earth elements in sedimentary rocks influence of provenance and sedimentary processes. In Reviews in Minerology. Vol. 21. Geochemistry and MinerologyofRare Earth Elements (eds Lipin, B.R. and McKay, G.A.). Society of America, Washington, DC. 

Equation (8.6) represents magmatic crystallization, eq. (8.7) metamorphic recrystallization, eq. (8.8) sedimentary processes and eq. (8.9) gas-phase deposition. 

Oxidation of transition metal ions in sedimentary processes Under the relatively oxidizing environments existing near the Earth s surface provided by aerated aqueous solutions in contact with the atmosphere, several... 

Factors similar to those in sedimentary processes are involved in metamorphic reactions. The susceptibility of a cation in a mineral to dissolution and recrystallization in a new phase depends on the relative stability of the ion in each crystal structure and the ease of removal of the ion from the structure. Thus, kinetic and thermodynamic factors again determine the fractionation of... 

Metamorphic geochemistry. Since element fractionation during metamorphism probably involves intergranular aqueous and saline solutions, factors similar to those in sedimentary processes operate during metamorphic recrystallization. Cations with highest CFSE that are least susceptible to substitution reactions (e.g., Cr3+, Ni2+) are the ones showing relative enrichments in remnant precursor minerals. 

Distribution and Sedimentary Processes within Estuarine Types... 

Pyroclastic ejected by volcanic emption Radiolarians a protozoon having a sihca skeleton Sedimentary processes whereby rocks (minerals) are formed from materials derived from other rocks by weathering, erosion, and transportation... 

Zeolites arise naturally by broadly two routes, one predominantly at low temperatures (below 40 °C) and associated with sedimentary processes, with the second being at higher temperatures and linked to volcanic and associated thermal processes. 

Relationship of volcanic and sedimentary processes in the formation of the banded iron-formations... 

In examining the particulars of the distribution, migration, and deposition of iron and silica in natural waters it is advisable to distinguish normal sedimentary processes and volcanic sedimentary processes. By normal sedimentary processes we mean the cycle weathered layer-transport-deposition in a sedimentary basin. The main distinguishing feature of volcanogenicsedimentary processes is the endogenetic source of the material and ex-ogenetic method of its deposition. 

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