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The sedimentary appearance of the thin laminations led to early interpretations that the deposits formed exclusively or mainly by exhalative processes onto the seafloor, hence the term SEDEX. However, recent study of numerous deposits indicates that shallow subsurface replacement is also an important process, in several deposits the predominant ...
For example, sedimentary exhalative deposits (SEDEX), are a class of ore deposit formed on the sea floor (sedimentary) by exhalation of brines into seawater (exhalative), causing chemical precipitation of ore minerals when the brine cools, mixes with sea water, and loses its metal carrying capacity.
Sedimentary exhalative (SEDEX) deposits account for 40% of total world zinc production, 60% of lead and a significant proportion of silver. Despite their economic importance however, sedex deposits are relatively rare. A worldwide compilation of sedex deposits indicates that about 70 are known, of which 24 have been or are being mined.
The aim of sedimentology, studying sediments, is to derive information on the depositional conditions which acted to deposit the rock unit, and the relation of the individual rock units in a basin into a coherent understanding of the evolution of the sedimentary sequences and basins, and thus, the Earth's geological history as a whole.
The key criteria for BHT ore deposits are; [11] Association with major sedimentary packages of sandstone and siltstone protoliths sequences in highly disturbed metamorphic terranes. A Proterozoic age is considered important, as no other major SEDEX lead-zinc deposits of this style are known from the Phanerozoic or Archean.
That is, deposits laid down by volcanism or by deposition of sediment derived from weathering detritus (clays, sands etc.). This includes all its fossil content and the information it yields about the history of the Earth: its past climate , geography, geology and the evolution of life on its surface.
The deposit is one of the world’s highest-grade deposits with more than 40% organic content and 66% conversion ratio into shale oil and gas. The oil shale is located in a single calcareous layer 2.5 to 3 metres (8.2 to 9.8 ft) in thickness and is buried at depths from 7 to 100 metres (23 to 328 ft). [ 6 ]
Sphalerite is a sulfide mineral with the chemical formula (Zn, Fe)S. [5] It is the most important ore of zinc.Sphalerite is found in a variety of deposit types, but it is primarily in sedimentary exhalative, Mississippi-Valley type, and volcanogenic massive sulfide deposits.