An overview of vis-nir-swir field spectroscopy - Spectral International
An overview of vis-nir-swir field spectroscopy - Spectral International
An overview of vis-nir-swir field spectroscopy - Spectral International
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The minerals include<br />
iron oxide (magnetite and hematite), iron carbonate (siderite and<br />
ankerite) and iron silicate (chlorite and amphibole, in particular grunerite<br />
and hastingsite).<br />
IRON STAGE<br />
Figure 66 - The iron stage <strong>of</strong> alteration shows<br />
biotite, iron-chlorite, cummingtonite, ankerite,<br />
siderite, hematite, and magnetite.<br />
Potassic Alteration<br />
The main ore stage is associated with potassium-iron alteration zones in which<br />
either sericite (at Olympic Dam and Prominent Hill) or K-feldspar (most common)<br />
prevail as the potassic-bearing phase.<br />
K-feldspar-biotite-pyrite-chalcopyrite<br />
At Olympic Dam,<br />
Potassic alteration occurs with hematite, sericite, chlorite, carbonate ± Fe-Cu<br />
sulphides ± uraninite, pitchblende and REE (bastnaesite) minerals prevail. It is<br />
locally superimposed on a magnetite-biotite alteration (Reynolds, 2000; Skirrow<br />
et al., 2002). The intense chloritization destroys the biotite. Quartz, fluorite,<br />
barite, carbonate, orthoclase, epidote and tourmaline can also be present.<br />
Titanite, monazite, perovskite and rutile may occur. The main uranium mineral is<br />
uraninite (pitchblende) with lesser c<strong>of</strong>finite and brannerite.<br />
52<br />
POTASSIC ALTERATION<br />
Figure 67 - Potassic is the most<br />
complex <strong>of</strong> the alteration phases. It<br />
includes tourmaline, biotite, iron-chlorite,<br />
epidote, REE-carbonate, monazite,<br />
muscovite, calcite, hematite, quartz.
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