Rivers, carbonate deposition

Thirty-two soil samples on a N-S traverse were collected from the brunisolic B-horizon (20 cm average depth) in May, 2008 over the drill-defined Northeast Zone of the Gay s River carbonate hosted massive sulfide (CHMS) Zn-Pb deposit, Stewiacke, Nova Scotia. This mineral target is buried by up to 10 m of exotic till and c. 10 m of gypsum, and so represents an ideal location to evaluate the exploration performance levels of partial digestions designed to extract labile elements from soil particle surfaces. 

Ion Ocean Inventory (10 mol) River Input Atmospheric- Evaporite Cycling S Ion Exchange Hydrothermal Activity Pyrite Burial or Other Carbonate Deposition ... 

Sedimentary lamination is also caused by the deposition of calcium carbonate and is important in most freshwater lakes where the clastic input from rivers is low. Carbonate deposits may be chemical or biogenic (see Box 1.1). As with phytoplanktonic production, the abiogenic (chemical) precipitation of calcium carbonate is seasonal, occurring during the warmer months. During this period carbon dioxide is removed from the water by planktonic photosynthesis, which causes water acidity to decrease and calcium carbonate to precipitate. From the equilibrium in Eqn 3.9c (Box 3.12) it can be seen that if the amount of C02(aq) decreases, more C02(aq) and carbonate are produced from bicarbonate, which increases the concentration of carbonate and promotes its precipitation. Subsequently, the water becomes more acidic and no longer supersaturated with respect to calcite (the main form of crystalline calcium... 

The above process, coupled with the fact that most carbonate-secreting organisms only thrive in clear waters — remote from rivers carrying significant amounts of solids washed from the land — accounts for the remarkably high purities of many carbonate deposits, which often exceed 98% of calcium plus magnesium carbonates. 

In the Changjiang River Estuary, the enormous primary production increased from west to east. Abundant matter from the Changjiang River was deposited here, where the sedimentation is faster, at about 2.0 cm/yr. In addition, the not too strong wave, tide, and coastal current are favorable for sedimentation. So there is a strong ability to fix carbon in the Changjiang River Estuary. Sedimentation flux can be used to assess the strength of sinking. 

Calcium carbonate (such as calcite, siderite, dolomite, and aragonite) is typically present in marine deposits and Pleistocene sediments deposited in river-banks and practically absent in deposits from ancient rivers and deposits of Miocene age. Calcium is generally the dominant exchangeable cation (56-82%) followed by magnesium (6-26%). An important parameter for behavior during aquifer transport is the calcite saturation index (SI = log[Ca ][C03 J/KcacOj)-... 

River terrace deposits are similar in character to those found in river channels. The pebbles of terrace deposits may possess secondary coatings due to leaching and precipitation. These are frequently of calcium carbonate that does not impair the value of the deposit, but if they are siliceous, then this could react with alkalies in high-alkali cements and therefore could be detrimental to concrete. The longer the period of post-depositional weathering to which a terrace deposit is subjected, the greater is the likelihood of its quality being impaired. 

The metro route of Lyublinsko-Dmitrovskaya line within the section from Petrovsko-Razumovskaya station to Mar ina Roshcha station is located in the northern part of Moscow within the moraine and fluvioglacial plains in the interfluvial area between the Moscow River and its tributary Yauza River. The surface levels immediately along the projected line vary from 160 to 1654 m a.s.l. In the geological cross-section, the roof of Carboniferous terrigenous carbonate deposits occur at a depth of 30-40 m. These deposits are overlain by Mid- and Upper Jurassic clay of 5-15 m thick, above which the 30-35-m-thick... 

The results for all sites are given in Table 5.1, and are best considered by dividing sites into three groups according to isotopic nature of the matrix (i) sites with most isotopically emiched matrix carbonates (Die Kelders and Swartkrans), (ii) sites with rather less enriched carbonates (Klasies River Mouth and Makapansgat), and finally (iii) a site with depleted deposit values (Border Cave). This is summarized in Fig. 5.5. The division also fortuitously provides a range of age depths in two categories. As indicated in Table 5.1, many of these data have been published elsewhere, but the purpose for which they are considered in combination here has not been previously attempted. 

These sites have deposit carbonates slightly less enriched than the previous group -3.2 2.1%o at Klasies River Mouth (where matrix values are... 

Class 5 (the least sensitive) soil include Kashtanozem, Brown soil and Sierozem soil zones in the Plateau of Inner Mongolia and the Loess Plateau, Desert soil zones in He-xi-zou-lang and the Talimu River Basin, Subalpine Steppe soil, Alpine Steppe soil and Alpine Desert soil in the Plateau of Tibet. These kinds of soils, belonging to the soil class of Xerosol or Alpine soil, consist of easy weathering minerals such as carbonate. They show alkaline reactions, with weak leaching and sparse vegetation. Those kinds of soils are insensitive to acid deposition. 

Petroleum is formed under the earth s surface by the decomposition of organic material. The remains of tiny organisms that lived in the sea and, to a lesser extent, those of land organisms were carried down to the sea in rivers along with plants that grow on the ocean bottoms combined with the fine sands and silts in calm sea basins. These deposits, which are rich in organic materials, become the source rocks for the formation of carbon and hydrogen, i.e., natural gas and crude oil. 

Reference materials that represent the primary deep-sea and coastal depositional environments and biological materials would solve many of the problems that radiochemists face in analysis of sediments from these settings. Radiochemists require reference materials comprising the primary end member sediment and biological types (calcium carbonate, opal, and red clay from the deep-sea and carbonate-rich, silicate-rich, and clay mineral-rich sediments from coastal environments and representative biological materials). Additional sediment reference material from a river delta would be valuable to test the release of radionuclides that occurs as riverine particles contact seawater. 

Table 4.6 (opal, carbonate and aluminosilicate) were chosen to provide end members for matrix analysis. These samples also could be blended to produce any mixture desired. Sampling sediments from well-studied depositional regions such as MANOP Site R in the North Pacific (for open-ocean red clay) and Florida Bay (for carbonate sediments) would offer a variety of supplemental information that is already available. In addition, the (Atchafalaya) river sediment would provide a useful link between those studying terrestrial and marine processes. 

Considerable geographic variability exists in the distribution of the source rocks contributing salts to river and groundwaters. As shown in Table 21.3, most of the evaporites, which are the dominant natural source of Na and Cl in river water, lie in marginal and endorheic (internal) seas. Some of these subsurfece evaporite deposits dissolve into groundwaters, which eventually carry Na and Cl into the ocean. Carbonates are the prevalent rock type between 15°N and 65°N. Precambrian-age crustal rocks and meta-morphic minerals predominate between 25°S and 15°N and north of 55°N. Shales and sandstones represent on average 16% of the terrestrial surfece lithology. 

Geological Setting The XY deposit is a stratiform Zn-Pb-dominated massive sulfide SEDEX orebody (Goodfellow 2004). It is situated near the base of the Duo Lake Formation within the Road River Group (Morganti 1979). The Duo Lake Formation is comprised predominantly of carbonaceous, sulfidic shales, with subsidiary cherty and phosphatic components in the strata immediately surrounding the ore horizon (Goodfellow et al. 1983). The Duo Lake Formation is underlain by carbonates of the Rabbitkettle Formation, which outcrop in parts of the valley in... 

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