Size Fraction in Stream Sediment
The size fraction of stream sediment samples in geochemical exploration in
Iran is generally -80 mesh and in some cases is -40 mesh.
Geochemical Signatures of Ore Deposits:
Elements have different paragenesis in different deposits, so geochemical
of every deposit are different from other deposits. For example, Pb-Zn skarn
deposits show Pb, Zn, Ag, Cu, Mn, As, Bi, W, Sn, F, Mo, Co, Sb, Cd, Au
geochemical anomalies but Irish type Pb-Zn deposits show Pb, Zn, Cu, Ag, Mn
geochemical anomalies. In this regard, two deposits with same mineralization
but different deposit models have different elemental paragenesis. Elemental
paragenesis in some deposits is totally different and in some cases is
similar. Arsenic accompanies many elements in their deposits including Cu,
Ag, Au, Zn,Cd,Hg, U, Sn, Pb, P, Sb, Bi, S, Se, Te, Mo, W, Fe, Ni, Co, and
PGE. Gold, same as arsenic,accompanies many elements in their deposits. In
summery, paragenesis relationships between elements are affected by geologic
characteristics of a region, deposit type, and the mechanism of ore forming,
so these relationships must be interpreted in regards of these parameters.
Heavy minerals are indicator of special elements, for example scheelite and
rutile are indicator of W and Ti respectively, so that heavy minerals show
paragenesis relationships same as elements. Some minerals such as ilmenite,
sphene, leucoxene, anatase, rutile, and brokite represent Ti mineralization.
Pyrite, pyrite oxide, chalcopyrite, cinnabar, orpiment, sphalerite, galena,
native copper, and native lead are the paragenesis of gold. Sphalerite,
galena, mimetite, native lead, cerrusite, barite, and fluorite show the Pb-Zn
ineralization.Some mineralization such as hematite, limonite, jarosite,
chlorite, epidote, biotite, and other altered minerals represent the
existence of altered area in the upstream of heavy mineral sample. The
existence of jarosite shows the existence of alunite, so that the
probability of epithermal mineralization will be increased. Tourmaline shows
the mineralization of Sn-W skarn types, shear zone-hosted gold, and etc. It
is important to keep in mind the presence of one particle of some ore
minerals such as gold, cinnabar, scheelite, cassiterite, sphalerite, and etc
in heavy mineral samples are valuable.