![]() Large scale tectonic events uplift these sequences to the surface and emplace them onto the continental crust. Ultramafic rocks are deep-sourced high temperature igneous rocks that tend to form within the earth’s mantle or at the base of sequences of oceanic crust. The nickel in these laterites is sourced from the ultramafic bedrock. Many factors affect the formation of nickel laterites, including the original rock the soil develops from, the climate, the rate in which weathering occurs, drainage of groundwater and the tectonic setting. The saprolite and limonite zones tend to contain the higher grades of Ni and can range from 1.5-3% and 1.2-1.7% respectively. The nickel in the limonite zone is found within the iron oxides such as goethite and hematite. The clay zone is rich in calcium, sodium, magnesium, iron and aluminum also known as smectites which can contain trace amounts of nickel. In the saprolite zone, nickel is contained within a series of mineral groups known as hydrous magnesium silicates, which consist of serpentines (((Mg, Fe) 3Si 2O 5(OH) 4)), chlorite ((Mg,Fe) 3(Si,Al) 4O 10, sepiolite Mg 4Si 6O 15(OH) 2♶H 2O and garnierites (Nickel bearing hydrous Magnesium silicates). The source of the nickel is typically from the mineral olivine (Iron-magnesium silicate), a predominant mineral in peridotites (a common type of ultramafic rock). CCĪs the original nickel bearing rock weathers into a soil, the nickel finds its way into multiple minerals throughout the weathered profile. Ore Minerals A sample of Garnierite, a mixture of nickel bearing minerals. Middle grade Ni deposits contain more than 1.5% Ni and high grade Ni deposits are greater than 1.8%. ![]() The average grade and tonnage of nickel –cobalt bearing laterites is 1.3 % Ni and 0.04% Cobalt at 56 Million tonnes. Economic laterite deposits tend to form in areas of low topographic relief as the difference in elevation can have an effect on the thickness of the deposit. These deposits consist of a predictable weathering profile that includes five “zones”: The un-weathered ultramafic bedrock, the weathered bedrock or “saprolite”, a clay-rich layer, limonite zone and a ferricrust or “iron cap”. These deposits develop from the mechanical and chemical breakdown of high temperature igneous rocks known as ultramafic rocks. Nickel Laterites are composed of long tabular bodies, over several hundred meters, but only tens of meters deep. Deposit Characteristics Physical Characteristics A generalized cross section of nickel laterite deposits A long time ago, bricks were carved out of laterites and used as building material in Asian countries such as India and Cambodia. The name “laterite” is a derivative of the latin word later, or “brick”. Laterites are a type of soil, rich in aluminum, magnesium, iron or in this case nickel that formed through prolonged chemical and mechanical weathering in wet, warm, tropical environments. ![]() With the global consumption of nickel growing at a rate of 4% per year (and increasing), it has now become apparent that new sources of nickel need to be found. In the last 10 years, the production of nickel from magmatic sulfide deposits has slowly decreased and begun to plateau. Over the last 60 years magmatic sulfide nickel deposits produced 60% of the world’s nickel. Although nickel Laterites make up 70% of the world’s nickel reserves, few of them become producing mines. Nickel is found in two types of deposits Nickel laterites and magmatic sulfide deposits.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |