Twenty-two rock samples were taken for shipboard analysis from Holes 1189A and 1189B. The samples from Hole 1189A are highly altered, with the exception of the uppermost sample (193-1189A-1R-1, 0-4 cm), which is a fresh dacite. Most samples analyzed from Hole 1189B are less altered than Hole 1189A samples and represent a different sampling scheme, following a great deal of trial and error with inductively coupled plasma-atomic emission spectroscopy (ICP-AES) methodologies.
A subset of samples obtained from Hole 1189A contains 5-10 wt% total sulfur and was initially measured with the ICP-AES using the sulfur method (see "Geochemistry" in the "Explanatory Notes" chapter). However, the results were found to be mismatched to the standard reference materials for sulfides and these samples were therefore reanalyzed using the method developed for igneous rocks with a dacite-rhyodacite composition (see "Geochemistry" in the "Explanatory Notes" chapter). Despite the high degree of alteration, there was, in general, a much better match with the matrix of the igneous rock standards. In about half of the analyzed rocks from Hole 1189A, the dominant portion of the total measured sulfur is sulfate-sulfur (i.e., anhydrite, barite, and other minor sulfates) and in the other half, the dominant phase is reduced sulfur, predominately in pyrite form. In Hole 1189B, the first two samples have very high sulfur contents with appreciable water-soluble sulfate.
The results of the ICP-AES, nitrogen, carbon, and sulfur (NCS), ion chromatography (IC), and gravimetric analyses of representative samples from Hole 1189A are given in Table T7, and those for Hole 1189B are given in Table T8. The samples are listed by assigned units, in order of increasing depth. Note that the ICP-AES analyses for all samples and standards were conducted on ignited powders as described in "Geochemistry" in the "Explanatory Notes" chapter. Two samples from Hole 1189B, although high in sulfide content, were also measured using the igneous method, and the data should, therefore, be used with caution. The reported ignited powder values are ordered with respect to major element oxides and expressed as weight percent. Values for loss on ignition (LOI) (in weight percent) of the unignited powders follow. The major element data precede the trace element concentrations (in parts per million [ppm]) for the ignited powders. The concentrations of the major elements in the ignited powders were recalculated using the LOI for the original rock composition, including volatiles, and the results are given in the lower half of Tables T7 and T8. In addition, gravimetric determination of soluble sulfate-sulfur in the unignited powder is reported at the bottom of the tables. In Tables T9 and T10, the data for NCS analysis of the unignited (pre-LOI) water and sulfur contents are presented.
As discussed in "Geochemistry" in the "Site 1188" chapter, a representative composite of small fragments (Hole 1189A) was collected from a bag labeled "1189A bulk residue" stored in the core splitter room. This included some off-cuts from sawing, and it is not certain what interval of the hole the fragments represent. The composite is probably biased toward the lower 30-50 m. The sample was sent by helicopter to the Commonwealth Scientific and Industrial Research Organisation (CSIRO) Division of Exploration and Mining, Sydney, Australia, for ICP-AES and neutron activation analysis (NAA) primarily to check the gold content, and the results are presented in Tables T11 and T12.
Owing to the internal inhomogeneity observed in the various units, the bias toward the samples with low sulfide contents, and the limited sample size (due to poor recovery), an interunit comparison should be made with caution. The variation of selected major oxide and trace element compositions with depth are plotted together with bulk mineralogy from XRD and the alteration log in Figure F117. The observed chemical variations are generally less pronounced than at Site 1188; they are consistent with the mineralogy and alteration style observed in thin section and XRD. However, in general, higher Na2O concentrations correspond to the presence of plagioclase observed in thin section, whereas K2O contents correlate with the proportion of illite and K-feldspar observed.
Only one fresh volcanic rock sample was analyzed from Hole 1189A (Unit 1; Sample 193-1189A-1R-1, 0-4 cm). This sample may be classified as a dacite, based on both total alkali vs. silica and using the International Union of Geological Sciences Subcommission on the Systematics of Igneous Rocks (CIPW norm) classification.
Three major alteration types have been identified in the cores from Hole 1189A: (1) GSC, (2) bleached (Bl), and (3) silicification (Sil). For more detailed descriptions of these alteration types, see "Hydrothermal Alteration". Table T7 shows the alteration styles assigned to each sample. Based on chemical composition alone, the three alteration styles do not seem very distinct. In general, the variations observed in the GSC altered rocks correspond to changes in phyllosilicate mineralogy and amounts of silica. The samples from Section 193-1189A-3R-1 (6-10, 59-63, and 70-73 cm, all at ~20 mbsf in Fig. F117) show the variance between the three alteration styles. The GSC altered rock has high water and sulfur contents and shows a clear decrease in Al2O3 and Na2O contents and an increase in CaO and Fe2O3 contents relative to the fresh dacite. In general, the changes in Fe2O3 and total sulfur can be attributed to the formation of pyrite, whereas the changes in Fe2O3 and MgO correspond to the formation of chlorite and clay minerals.
The NAA analyses conducted on the composite sample from Hole 1189A (Table T12) reveal that this sample contains 20 ppb Au, which is higher when compared with the composite samples from Site 1188, but is not anomalous in an economic geology sense.
The upper 100 m recovered from Hole 1189B is extensively altered, and recovery was very low; only two samples were analyzed from this interval. Six samples were analyzed from the lower sequence of Hole 1189B. The variations with depth of selected major oxide and trace element compositions are plotted together with bulk mineralogy in Figure F118. All samples above 147 mbsf are classified as GSC altered, whereas the last two samples represent the silicification rock alteration style. In general, SiO2, CaO, and Na2O contents increase below 100 m, which is in agreement with the increases in plagioclase and quartz contents. The increase in SiO2 is relative, because the first sample (193-1189B-1R-1, 20-30 cm) is an unusually soft, clay-rich alteration product of vesicular dacite, dominated by illite, mixed-layer clays, and pyrite, and is particularly low in silica. The second sample (193-1189B-8R-1, 7-9 cm) is a K-feldspar-bearing, brecciated rock with a stockwork sulfide overprint. Therefore, these two samples are not mineralogically comparable with samples from the lower sequence. They have overall low silica, CaO, and Na2O, high Al2O3 contents, and higher TiO2, Fe2O3, and K2O than the deeper samples. Below 128 mbsf, the water and sulfur contents decrease with depth, and S contents are particularly low, whereas Sr and the Zr/TiO2 ratio (Zr in ppm, TiO2 in wt%) are higher. This latter feature is consistent with the change from aphyric to sparsely porphyritic rock (dacite to rhyodacite parent) (see "Igneous Petrology") at ~100 mbsf.
One water sample was collected by the water-sampling temperature probe (WSTP) in Hole 1189B at 130 mbsf. The in situ measured water temperature was 55°C. Immediately after recovering the sampling tube, the pH, alkalinity, and salinity were determined. The water chemistry was measured using IC and ICP-AES methods (see "Geochemistry" in the "Explanatory Notes" chapter), and the results, as well as the pH, alkalinity, and salinity values, are reported in Table T13. The measured pH and alkalinity are slightly lower and chloride, calcium, strontium, and particularly sulfate are higher than standard seawater. The anomalously high value for manganese (236 µmol/L), which is similar to the first water sample from Hole 1188B (278 µmol/L), reflects leaching from altered host rocks, which tend to be conspicuously depleted in this element.
In comparison with the water data from Site 1188, most ion concentrations are slightly elevated. The pH is lower by ~1, whereas sulfate and strontium values are ~15%-25% higher. In addition, in Hole 1189B, the concentration of lithium is almost five times higher, iron about four to ten times higher, and calcium about two times higher than concentrations in the three samples from Holes 1188B and 1188F, indicating a larger hydrothermal input and possibly also some dissolution of anhydrite (increased sulfate).