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Sample I.D SiO 2 CaO FeO ThO 2 MnO UO 2 PbO Na 2O Y 2O 3 P 2O 5 Total<br />

Chemical<br />

Pb age<br />

C29-217B-28 1.03 2.96 0.25 0.06 0.25 83.60 5.66 0.24 0.64 0.10 95 420<br />

C29-217B-29 0.44 2.35 0.27 0.06 0.25 84.03 6.28 0.34 0.62 0.07 95 464<br />

C29-217B-30 0.50 2.19 0.25 0.03 0.21 82.86 5.60 0.32 0.80 0.09 93 419<br />

C29-217B-31 2.65 4.91 0.10 0.02 0.58 81.79 3.84 0.12 0.56 0.08 95 291<br />

Table 4.1. Results of the electron microprobe analyses for uraninite occurrences in the<br />

Coronation Hill deposit with average chemical composition and calculated chemical Pb age.<br />

The composition is reported in weight percent and the age in Ma.<br />

4.5.2.1.2. Chlorite crystal chemistry<br />

Pre-ore Chl 1<br />

chlorite is Mg-rich with a calculated structural formula of<br />

Mg 3.04 Al 2.53 Fe 0.47 (Si 3.3, Al 0.7 )O 10 (F 0.1 Cl 0.01 (OH) 7.89 ), corresponding to clinochlore (Deer et<br />

al., 1992). Formation temperatures are near 160°C (Table 4.2), based on site occupancy<br />

(Cathelineau, 1988). Syn-ore Chl 2 chlorite is similar in composition to pre-ore Chl 1 chlorite<br />

with a structural formula of Mg 3.26 Al 2.52 Fe 0.89 (Si 3.03, Al 0.97 )O 10 (F 0.16 Cl 0.01 (OH) 7.73 , but with<br />

formation temperatures near 250°C (Table 4.2). Post-ore Chl 3 chlorite has a structural<br />

formula of Mg 2.67 Al 2.52 Fe 0.49 (Si 3.03 Al 0.97 )O 10 (F 0.16 Cl 0.01 (OH) 15.8 ) and records formation<br />

temperatures near 100°C (Table 4.2). Chl 1 , Chl 2 and Chl 3 chlorites are low-Fe chlorite with<br />

low Fe/Fe+Mg ratios (0.14 to 0.21) and high Si contents (Table 4.2), likely reflecting the<br />

chemistry of the felsic quartz-feldspar porphyry host rock with which the hydrothermal<br />

fluid has reacted. The composition of these chlorites includes trace amounts of Mn, F, and<br />

Cl. Syn-ore Chl 2 chlorites have higher F contents (0.16 wt %; Table 4.2).<br />

Coronation Hill Deposit<br />

El Sherana Deposit<br />

Pre-Ore Chl 1 Ore Stage Chl 2 Post-Ore Chl 3 Pre-Ore Chl 1 Ore Stage Chl 2<br />

Oxides Wt % n=16 n=53 n=8 n=22 n=61<br />

SiO2 33.48 30.76 35.64 26.11 28.44<br />

TiO2 0.01 0.01 0.01 0.02 0.02<br />

Al2O3 21.78 21.78 21.88 18.67 17.55<br />

162

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