The three jasperoid samples from Site 1189 are described in Table T1. Figures F2, F3, F4, F5, F6, F7, F8, F9, F10, F11, F13, F14, F15, and F16 illustrate key petrographic characteristics.
The common feature of the jasperoids is the presence of cores clouded by tiny hematite inclusions within dominant quartz (Figs. F3, F4, F9). The cores are sharply bounded, commonly with outlines indicating a former doubly terminated pseudohexagonal prismatic habit. In Sample 193-1189B-11R-1 (Piece 3, 14–17 cm; CSIRO 142714), there are also strange frondlike aggregates (Fig. F12) and possible earlier cavity linings (Fig. F14) of hematite, overgrown by quartz. The hematite flakes are too small to display diagnostic optical properties, but are identified as such by their bright red internal reflections that are particularly strong when observed in reflected light with crossed polarizers. However, some more yellowish brown flakes in the frond structures may be goethite.
Quartz grains vary in overall size between the samples and range from seriate where closely packed to euhedral where separated by open pores or microdrusy cavities. Larger druses, and in one case an open fracture, are lined by well-crystallized quartz generally free of hematite inclusions (implying crystallization from a more reduced fluid). Euhedral pyrite, subordinate overgrowths of anhydrite, and very rare globules of clay also line or fill some cavities. Some disseminated pyrite euhedra and subhedra, most distinctly larger than the jasperoidal quartz, are not so clearly related to drusy structures and may have formed by replacement of quartz matrix after passage of H2S-bearing fluid. There are no distinct boundaries between quartz with hematitic cores in the main body of the jasperoids and quartz lining the cavities, the latter apparently representing a continuation of the same quartz crystallization episode as the margins of jasperoidal grains.
Thin selvages of clear quartz surround wallrock fragments in two of the samples (Figs. F2, F6, F8), although in Core 193-1189B-6R (Fig. F1) they are present in analyzed Piece 5 (Fig. F8) but lacking in sectioned Piece 2 nearby (Fig. F10). These selvages also appear to be continuous outgrowths from the jasperoidal quartz (Fig. F7), but at the immediate contacts they may show grain-scale jagged replacement of wallrock.
Narrow veinlets of selvage quartz (Fig. F7) or, where selvages are lacking, of jasperoidal quartz with varying hematite abundance (Figs. F10, F11) locally cut into or across the wallrock fragments. Adjacent to these there may be some silicification of wallrock by poikiloblasts of quartz (with numerous clay inclusions) that tend to have epitaxial orientations relative to adjacent vein quartz (Fig. F10). One such veinlet fills a dilated microfracture that wedged apart a plagioclase phenocryst in wallrock (Fig. F10).
The shapes of wallrock fragments are very irregular (Figs. F2, F8), too much so to permit their reconstruction as a simple jigsaw-fit hydrothermal breccia. Sample 193-1189B-6R-1 (Piece 2, 13–15 cm) contains a variety of fragments with differing microfabrics, some perlitic, some with more massive fabrics, and some vesicular. Evidently they have been mixed together by brecciation or hydrofracturing from separate, though conceivably adjacent, sources and their outlines modified by solution or replacement. Similar features occur in many sulfide-rich, nonjasperoidal quartz veins or breccia matrixes in adjacent core pieces.
The three jasperoid samples are composed primarily of Si, Fe, and S (Table T2), together with minor Ca attributable to anhydrite and traces of other lithophile (normally "major") elements (Ti, Al, Mg, Na, and K, but not P) likely to be mainly present in small wallrock fragments unavoidably left in the analyzed powders. Manganese contents are particularly low. Table T3 lists normative mineralogy computed by allocating S (after calculating anhydrite abundance from Ca) with Cu and Fe to chalcopyrite then with Fe to pyrite. The abundance of hematite, calculated from residual Fe, is comparatively small in all samples, while quartz is by far the dominant normative component. Normative proportions of pyrite and lesser chalcopyrite in two samples agree with microscope observations. As evident modally, normative anhydrite is most abundant yet still minor in Sample 193-1189B-11R-1 (Piece 3, 14–16 cm; CSIRO 142714). Wallrock contaminants (computed from Al2O3, with reference to nearby wallrock samples) amount to 2–3 wt%.
Detailed discussion of wallrock compositions is not justified given their small contribution, possible analytical errors, and the assumptions made in normative calculations, but their Ti/Al ratio is lower by a factor of ~2 relative to altered volcanic rocks analyzed by the author from nearby cores. This, together with their apparent Cr content, suggests somewhat more mafic dacite parents.
Phosphorous contents are higher than likely wallrock contributions in jasperoid Samples 193-1189A-7R-1 (Piece 17, 99–102 cm; CSIRO 142697) and 193-1189B-11R-1 (Piece 3, 14–16 cm; CSIRO 142714) by a factor of ~50, these being the two samples where trace apatite was noted (Figs. F6, F13). LOI for the single Sample 193-1189A-7R-1 (Piece 17, 99–102 cm; CSIRO 142697), where this was determined, is inexplicably high, more so than expected to arise from wallrock contaminants, misidentification of goethite, rare observable fluid inclusions, or absence of an adjustment for pyrite oxidation, which would cause gain on ignition. Low analytical totals for the other two samples (Table T1) hint at a similar problem.
Applying data obtained from nearby altered wallrock samples to the normative ratios, the lithophile trace elements V, Ga, and Th are explicable by the presence of wallrock contaminants. Li, however, is distinctly enriched (~x500), while Rb (~x5), Cs (~x5 to x10), and, in two samples, the rare earth elements (REE) (see below) are moderately enriched. The mineralogical habitat of apparent excess Li, Rb, and Cs in the jasperoid is undetermined. U is distinctly enriched (~x30) in Sample 193-1189A-7R-1 (Piece 17, 99–102 cm; CSIRO 142697) and ~x200 in Sample 193-1189B-11R-1 (Piece 3, 14–16 cm; CSIRO 142714), and slightly so (~x5) in Sample 193-1189B-6R-1 (Piece 5, 45–55 cm; CSIRO 142707), correlating with P (apatite?) abundance. Though their levels in the jasperoids are low, Sr (~x20) and Ba (~x4) are significantly enriched only in Sample 193-1189B-11R-1 (Piece 3, 14–16 cm; CSIRO 142714) with the higher anhydrite content, but are explicable as wallrock contaminant in the other samples.
Chondrite-normalized REE profiles for the jasperoids (Fig. F17A) show two contrasting patterns. Relative to the other jasperoids, Sample 193-1189B-6R-1 (Piece 5, 45–55 cm; CSIRO 142707) has lower REE abundances and no pronounced Eu anomaly. Altered wallrocks at Site 1189 mostly show distinctly negative Eu anomalies (Fig. F17B), and it is difficult to account for the jasperoid REE patterns by wallrock contaminants in the samples. Bach et al. (2003) report highly variable REE abundances and chondrite-normalized patterns for vein anhydrites, with both positive and negative Eu anomalies. Considering their minor anhydrite content, REE abundances in this mineral do not explain the jasperoid patterns. It appears that the REE in Samples 193-1189A-7R-1 (Piece 17, 99–102 cm; CSIRO 142697) and 193-1189B-11R-1 (Piece 3, 14–16 cm; CSIRO 142714) particularly are contained mainly in another component, possibly apatite.
Apart from Cu, chalcophile trace elements have low and variable abundances in the jasperoids, but Co, Ni, Zn, Ge, As, Mo, In, Sb, Te, Tl, Pb, and Bi contents are, in most cases, all higher than expected from wallrock contributions by factors ranging from x10 to x500. Except for In, which is higher in the chalcopyrite-bearing samples, there is no clear correlation with observed sulfide abundances. Elevated Cd in Sample 193-1189B-11R-1 (Piece 3, 14–16 cm; CSIRO 142714) is accompanied by elevated Zn, possibly arising from sphalerite overlooked under optical microscope.