| Budget Amount *help |
¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1992: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1991: ¥1,600,000 (Direct Cost: ¥1,600,000)
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| Research Abstract |
In this report, consideration is given to the chemical behavior of several elements and constitute minerals according to their depth in the weathering profile of the pulot, Rio Tuba and Hinatowan nickel deposits in the Philippines.
In order to present the profile of the ore deposit in a model, on the basis of mineralogical charter, it can be divided into two layers from surface to bed rock, i. e., the upper part is compose of oxidized red laterite ore and the lower one, so-called garnieritic ore, actually saprolite or decomposed serprntinite.
A clear difference exists between the chemical composition and constitute minerals in the upper and lower layers. The principal minerals are goethite in the upper layer and serpentine is most common in the lower one with small amount of clay minerals. In some cases, a thin secondary silica layer is intercalated near the boundary.
It has been revealed that there is an increase of element Fe_2O_3 together with a decrease of elements SiO_2 and MgO, of w
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hich phenomenon is characterized by respective alternating stage in the bed rock - saprolite- laterite sequence. Minor elements show no difference between saprolite and laterite.
Iron in laterite occurs mainly as hydrated oxide (goethite), but due to progressive dehydration, higher gravity oxides chromite and hematite and maghemite may appear in increasing amount toward the surface. The iron content decrease toward the lower part of laterite zone. Nickel is concentrated with goethite in laterite and partly with hydrous nickel-iron- magnesium silicates in the saprolite layer.
In the ores, chemical components are closely related to the particle size of the constitute minerals. In the laterite - transitional-saprolite- sequence, a common variation range and tendency in chemical composition (both major and minor components) for each particle size can be seen. However, taking samples with the same particle size the chemical composition obviously differed, representing the characteristics of the components for each zone. This fact indicates the zone of each characteristic layer corresponding to the depth and the degree of size reduction which depends on the dissolution-residual of the mother rock component occurring in the formation process of weathering (lateritization). Less
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