Análisis de las muestras de arcilla industrial

Chemical compositions of the Fe-Mn±Si–rich rocks from Bukit Botol and Bukit Ketaya deposits were determined to assess their origin (Tables 5.1 and 5.2), because diagnostic elemental assemblages of major, minor and trace elements can be used to distinguish Fe-Mn deposits that are formed under different geological environments. The analysed samples were from outcrops that include five samples from the Bukit Botol deposit and twelve samples

CHAPTER 5 MINERALISATION AND ALTERATION

117

from the Bukit Ketaya deposit. Methods are described in section 5.2, and sampling details are listed and shown in Appendix II.

Table 5.1. Major and trace elements of Fe-Mn layer from the Bukit Botol deposit, Central Peninsular Malaysia.

Bukit Botol

Element 405 301[a] 301[b] 302[a] 302[b] wt% SiO2 2.96 4.95 4.91 3.68 4.66 TiO2 0.099 0.054 0.064 1.13 1.14 Al2O3 5.58 3.76 3.84 2.56 2.62 Fe2O3 1 46.41 35.72 35.82 72.96 73.2 MnO 25.36 32.67 32.87 5.52 5.56 MgO 0.06 0 0 0.1 0.12 CaO 0 0.02 0.04 0.02 0.02 Na2O 0.03 0.1 0.12 0.02 0.04 K2O 0.21 0.29 0.31 0.02 0.02 P2O5 0.193 0.112 0.112 0.204 0.204 BaO 3.53 2.30 2.30 0.560 0.562 CuO 0.204 0.206 ZnO 0.809 0.258 0.256 PbO 5.60 5.61 1.47 1.50 Loss inc.S- 14.30 12.32 12.70 9.33 9.19 Total 99.54 98.35 99.16 97.58 98.84 S 0.10 0.16 0.15 0.25 0.25 ppm DL2 Sc 8.8 5.3 6.1 8.5 7.6 1.5 Ba 31617 20600 20600 5016 5034 4 V 18.1 47.5 43.9 194.9 197.7 3 Cr 7.1 4.6 5.2 44.5 44.3 1 Ni 7.8 9.6 8.3 <1 <1 1 Cu 290 1630 1645 1293 1283 1 Zn 6500 2073 1655 782 783 1 As 135 386 391 3696 3787 3 Rb 5.2 4.5 3.9 1 1.2 0.5 Sr 52.9 22.9 22.1 5.7 5.4 1 Y 13.9 32.2 33.9 106 105 1 Zr 42.6 13.3 13.6 287 293 1 Nb 0.8 <0.5 <0.5 16.0 18.4 0.5 Sn 6.7 16.3 13.6 11.7 12.6 1 Pb 668 51987 52079 13646 13925 1 Bi <2 8.4 10 42.7 42.4 2 U 2.0 9.8 12.2 4.4 8.3 2 Th 2.0 2.0 2.0 2.0 2.0 2 La 30.1 72.2 72.0 28.8 28.6 4 Ce BDL3 _{BDL BDL BDL BDL 6} Nd BDL BDL BDL BDL BDL 4

Notes: Major elements: XRF, trace elements: ICP-MS methods

1_{Total Fe as Fe} 2O3 2

DL = Detection limits (ppm)

3

BDL = Below detection limits (ppm)

At Bukit Botol, the Fe-Mn variety contains high concentrations of iron (Fe2O3 = 35–73 wt %),

manganese (MnO = 6–33 wt %) and alumina (Al2O3 = 2.6-5.6 wt %) but are silica poor, with

low contents of all other elements (i.e., rarely exceed 1 wt % with the exception of wt. percent of BaO and PbO in some Ba- and Pb-rich samples). However, some elements still have higher ranges in concentration relative to crustal abundances, notably Cu (290 to 1645 ppm), Pb

CHAPTER 5 MINERALISATION AND ALTERATION

118

(between 600−52000 ppm), Zn (782−6500 ppm) and Ba (5016−20600 ppm). In addition, all samples have also relatively high As (135−3787 ppm) and U (2−12.2 ppm) contents.

Table 5.2. Major and trace elements Fe-Si layers from the Bukit Ketaya deposit, Central Peninsular Malaysia.

Bukit Ketaya

Element BK02 BK03 BK04 FeMn1-KNN FeMn2 BK05 BK05a BK13 BK13a BK13b FeMn3 Mn1 wt% SiO2 90.12 90.18 96.10 64.49 65.05 5.11 2.58 19.53 6.61 13.07 7.98 16.48 TiO2 0.30 0.23 0.42 0.277 0.601 0.25 0.28 0.12 0.10 0.11 0.351 0.405 Al2O3 3.67 6.78 1.43 0.44 1.68 0.13 0.12 0.25 0.50 0.19 0.12 1.77 Fe2O31 4.22 0.43 0.93 33.98 31.29 68.45 73.33 79.71 92.87 85.53 91.23 78.42 MnO 0.00 0.00 0.01 0.001 0.001 0.01 0.02 0.01 0.01 0.01 0.005 0.01 MgO 0.03 0.04 0.01 0.03 0.04 0.01 0.02 0.01 0.01 0.01 0.03 0.06 CaO <0.01 0.01 <0.01 0.01 0.02 0.09 0.10 0.07 0.05 0.08 0.08 0.07 Na2O 0.15 0.26 0.08 0.03 0.12 0.13 0.13 0.03 0.03 0.03 0 0.01 K2O 0.52 0.59 0.16 0.02 0.22 <0.01 <0.01 0.01 0.02 <0.01 0.01 0.02 P2O5 0.02 0.02 0.03 0.014 0.034 0.03 0.03 0.05 0.02 0.01 0.015 0.127 BaO 0.041 0.062 0.013 16.51 15.32 0.043 0.094 0.574 0.141 CuO ZnO 0.000 0.000 0.000 0.002 0.002 0.002 0.004 0.002 PbO 0.002 0.001 0.002 0.064 0.053 0.011 0.021 0.016 Loss inc.S- 1.00 1.52 0.51 0.27 0.40 0.99 0.68 0.18 0.35 0.49 0.27 1.68 Total 100.07 100.12 99.68 99.57 99.45 91.79 92.64 99.98 100.62 100.07 100.23 99.05 S 0.01 0.01 0.02 0.03 0.04 3.61 3.37 0.06 0.06 0.21 0.10 0.20 ppm DL2 Sc 7.8 6.2 6.3 3 11.6 4 4 4 4 4 11.2 7.2 1.5 Ba 364 553 121 37.8 324 148000 137000 388 841 5140 321 504 4 V 3 4 8 16.7 29.2 32 38 8 16 20 29.5 14.1 3 Cr 1.5 1.7 3.3 1.5 10.5 2.0 2.0 3.4 7.8 5.9 9.1 1 1 Ni 2 4 3 2.1 4.7 13 8 <4 <4 <4 4.5 2.3 1 Cu 15 15 35 148 217 72 67 272 214 232 217 4.2 1 Zn 2 1 1 6.4 8.6 16 17 16 29 19 7 1.4 1 As 4 3 4 70.7 57.4 228 243 70 162 177 56.2 <3 3 Rb 25 25 6.9 1.5 8.2 2.8 2.7 1.6 2.3 1.3 8 39.8 0.5 Sr 67 52 58 14.3 58.9 1576 1472 23 25 55 58.3 51.6 1 Y 14.1 13.7 12.8 15.0 30.6 3.6 6.2 6.5 2.0 6.0 29.8 25.5 1 Zr 280 234 278 222 649 63 112 72 20 62 651 337 1 Nb 10.5 9.5 9.6 10.8 13.8 0.9 2.0 3.6 2.0 3.8 13.9 15.4 0.5 Sn 7 2 19 11.8 135 98 89 15 44 126 136 19.7 1 Pb 21 11 18 30.4 85.8 595 492 106 195 149 86.6 9.3 1 Bi 4 <2 3 <2 15.1 84 119 75 101 18 15.2 5.8 2 U 4.0 2.9 5.6 2.5 7.8 4.0 4.0 4.0 4.0 4.0 7.7 3.4 2 Th 11.3 7.7 9.8 11.1 14.4 2.0 2.0 2.0 2.0 2.0 13.3 12.9 2 La 18 22 29 12.0 29.0 BDL BDL 10 <4 5 29.9 30.1 4 Ce 34 46 63 10.0 61.5 BDL BDL 4 <6 BDL 59.4 72.5 6 Nd 12 16 28 10.7 33.3 BDL BDL 10 <6 <6 33.4 28.7 4

Notes: Major elements: XRF, trace elements: ICP-MS methods

1

Total Fe as Fe2O3 2

DL = Detection limits (ppm)

3

BDL = Below detection limits (ppm)

The Fe-Si layers of Bukit Ketaya are geochemically distinct from the Fe-Mn layer of Bukit Botol. Two varieties are distinguished based on their chemical compositions, and these correspond with the field divisions (Fig. 5.6). The massive hematite-silica layer (Table 5.2) has high Fe2O3 contents (68 to93 wt %) and has a lower silica composition (SiO2 = 3-20 wt %).

CHAPTER 5 MINERALISATION AND ALTERATION

119

silica (SiO2 = 65-96 wt %), iron (Fe2O3 = 1-34 wt %) and alumina (Al2O3 = 0.5-6.8 wt %).

MnO contents are uniformly low (<0.1 wt %) with all other constituent elements less than 1 wt % in both types. In contrast to the Bukit Botol, all Fe-Si layers constitute uniformly low to moderate Cu, Pb and Zn content, whereas concentrations of Ba, As, U are relatively high. However, the massive hematite-silica layer has slightly lower concentrations of these elements than the microbreccia Fe-oxyhydroxide textures.

A ternary diagram in terms of Al, Fe, and Mn shows the relative contributions of hydrothermal (Fe, Mn) and detrital (Al) material to the Fe-Mn and Fe-Si samples at both the Bukit Botol and Bukit Ketaya deposits, together with well-defined fields of hydrothermal, non-hydrothermal sediments after Böstrom and Peterson (1969) and modern chemical precipitates or metalliferous sediments from Böstrom (1973) and Hein et al. (2005) (Fig. 5.13). As shown in the diagram, the Fe-Si samples are considerably more enriched in hydrothermal material, except for a few samples from the Bukit Ketaya deposit that plot towards the Al join due to their high detrital content. In comparison, the Fe-Mn samples at Bukit Botol deposit exhibit a similar compositional range to modern hydrothermal chemical sediments of the East Pacific Rise.

CHAPTER 5 MINERALISATION AND ALTERATION

120

Fig. 5.13. Al-Fe-Mn (wt%) ternary diagram showing the composition of Fe-Mn and Fe-Si samples from both the Bukit Botol and Bukit Ketaya deposits relative to the compositional fields of hydrothermal and non- hydrothermal sediments. Fields of hydrothermal and non-hydrothermal sediments are from Böstrom and Peterson (1969), EPR sediments, metalliferous hydrothermal sediments and Fe-Mn crusts from Böstrom (1973) and Hein et al. (2005). Annotation: EPR = East Pacific Rise.

The SiO2 - Al2O3 diagram (Fig. 5.14A) is useful to distinguish hydrothermal deposits from

hydrogenous deposits (Bonatti, 1975; Wonder et al., 1988). In the SiO2 - Al2O3 discrimination

diagram of Wonder et al. (1988), the data from the Bukit Botol, Fe-Mn samples fall in the area for hydrogenous field and deep sea sediments, whereas the Bukit Ketaya, Fe-Si samples are clearly plotted in the hydrothermal field (Fig. 5.14A)

CHAPTER 5 MINERALISATION AND ALTERATION

121

Fig. 5.14. Discrimination diagrams of Fe-Mn and Fe-Si samples from both the Bukit Botol and Bukit Ketaya deposits. A. SiO2-Al2O3 diagram showing the Bukit Botol Fe-Mn samples fall in the hydrogenous area, whereas

the Bukit Ketaya Fe-Si samples are plotted on the hydrothermal field. B. Composition of Fe-Mn and Fe-Si samples in term of Fe/Ti vs. Al/(Al+Fe+Mn). Curve represents the ideal mixing line between hydrothermal sediments with terrigenous or pelagic sediment (modified from Barrett, 1981; Wonder et al., 1988).

Although the Bukit Botol samples are hydrogeneous, a hydrothermal origin cannot be ruled out as the SiO2-Al2O3 diagrams do not consider the possibility of in-situ subsurface

replacement and infill, an origin which has been demonstrated for the Tetsusekei of Japan (e.g., Kalogeropoulus and Scott, 1983). Regarding the presence of clastic constituents that are

CHAPTER 5 MINERALISATION AND ALTERATION

122

incorporated in some samples, the Al is primarily considered to be a measure of detrital or clastic grain abundance (Crerar et al., 1982).

The Fe/Ti vs. Al/ (Al + Fe + Mn) diagram (Fig. 5.14B) is efficient in testing the presence of hydrothermal chemical sediment compositions (Barrett, 1981). Pure hydrothermal chemical sediments contain high Fe/Ti ratio and less Al whereas contamination of these sediments by addition of detrital or volcanic material dilutes the Fe/Ti and enriches the proportion of Al with respect to the hydrothermal elements, Fe and Mn (e.g., Barrett, 1981; Wonder et al., 1988). In this diagram, the Fe-Mn and Fe-Si samples from Bukit Botol and Bukit Ketaya deposits plot on an ideal mixing line between modern metalliferous seafloor hydrothermal sediments (e.g., Red Sea and East Pacific Rise) and pelagic or terrigenous sediments (e.g., Pacific Ocean). In fact this data suggests that Pacific Ocean clay is not extreme enough in terms of Al/ (Al + Fe + Mn) to comprise an end member in the Bukit Ketaya deposit. Thus, this pattern reveals a major input of hydrothermal source for the formation of the Fe-Mn±Si layers in both the Bukit Botol and Bukit Ketaya deposits. Additionally, the trends towards the pelagic or terrigenous sediment implies that both the Bukit Botol and Bukit Ketaya Fe-Mn and Fe-Si layers had significant clastic input although they do not allow differentiation between host rock replacement and mixing with detrital material.