K -Ar dating of illite-bearing clays from eight locations in Jenolan Caves yielded ages from 394 Ma (Early Devonian) to 258 Ma (Late Permian) (18 dates of individual size fractions). There were two distinct clusters among the dates. Seven dates ranged from 342 to 335 Ma (Carboniferous, Visean). Three dates ranged from 394 to 389 Ma (Early Devonian). Fission track dating of 11 zircons from one sample yielded pooled ages of 345.9 Ma (nine grains) and 207.2 Ma (two grains). XRD peak width measurements and SEM studies indicated that the clays are well crystallised and showed no signs of transport. This suggests that the clays formed and matured in place in the caves. Sedimentary strata of Visean to Namurian age are not found in the surroundings of the caves. XRD peak width measurements, SEM studies, and additional K -Ar illite dating rule out illite-bearing materials in the immediate catchment of the caves as a source for the Carboniferous clays. The most likely origin for the Carboniferous clays is from volcaniclastics, associated with the emplacement of Carboniferous granites, entering the caves. The volcaniclastics reacted with thermal waters, which had excavated the caves, altering feldspars and glasses to kaolinite and illite. The Early Devonian clays are interpreted as volcaniclastic palaeokarst deposits related to an unconformity at the base of the overlying Lower Devonian volcanics. Whatever their origin, the Carboniferous clays are hundreds of millions of years older than absolute dates of cave deposits reported in recent reviews and appear to set a record for the absolute age of deposits found in currently open caves.
Elsmoreite, WO 3 •0.5H 2 O (IMA 2003-059), is a new mineral species from the Elsmore tin deposit, Elsmore, in the New England region of northern New South Wales, Australia. The name is derived from the locality. It occurs as a white, microcrystalline powder (luster could not be observed) formed as a result of the oxidation of ferberite in the oxidized zone of weakly mineralized granitic pegmatite dykes containing Sn, W, Mo and Bi minerals, hosted in pegmatitic greisen veins in a granite stock. The mineral is cubic, space group Fd3m, with a 10.203(1) Å, V 1062.1(2) Å 3 , Z = 16, D calc 6.025 g cm-3 , using refi ned unit-cell data from natural material and the ideal formula WO 3 •0.5H 2 O. The density of the natural material could not be measured. The seven strongest lines in the X-ray powder diffraction pattern [d in Å(I)(hkl)] are: 5.884(100)(111), 2.944(78)(222), 3.075(62)(311), 1.804(23)(440), 1.964(17)(511), 1.725(14)(531) and 1.538(14)(622). Tungsten was the only cation detected by electron-microprobe analysis. An average of fi ve spot-analyses (W) on individual grains and a single thermogravimetric analysis for H 2 O gave 96.0% WO 3 and 3.3% H 2 O, yielding the formula WO 3 •0.44H 2 O, based on one W atom, and ideally WO 3 •0.5H 2 O. Elsmoreite is identical to the cubic synthetic phase of the same composition, and whose single-crystal structure is known. The structure is based on a defect pyrochlore lattice. Because of the minute grain-size of the natural material, its physical and optical properties were determined on synthetic WO 3 •0.5H 2 O. Microcrystalline octahedral crystals of WO 3 •0.5H 2 O are colorless with a white streak, translucent, and possess an adamantine luster, with a very high index of refraction, 2.24 ± 0.005 (white light). No luminescence was observed. The compatibility index (CI) is-0.164, which is classed as poor. Elsmoreite is brittle, has no apparent cleavage, a splintery fracture and a Mohs hardness of approximately 3. Crystals are octahedral, some of which seem to be twinned on the spinel law. The cubic tungstic acid is closely related to ferritungstite, alumotungstite and jixianite.
Lanthanite-(Nd) occurs in tuffaceous, altered andesitic agglomerate in the Whitianga quarry, Coromandel Peninsula, New Zealand. The usual platy habit is represented, together with more unusual blocky equant crystals. The former show the new forms {201}, {102} and {111}, and the latter, {111}. ICP-MS analyses show that the distribution of REE (and Ga) is consistent with the formulation (Nd 0.63 La 0.59 Ce 0.35 Pr 0.15 Sm 0.10 Gd 0.069 Y 0.06 Eu 0.03 Dy 0.02 Ga 0.01) ⌺2.04 (CO 3) 3 •8H 2 O; the REE sum of 2.04 is due solely to rounding errors. The Þ nd represents the Þ rst occurrence of this rare mineral in New Zealand. The mineral formed under comparatively oxidizing conditions. The REE are probably scavenged by warm waters circulating through underlying greywackes of the Manaia Hill Group. We also characterized the lanthanite-(Nd) by X-ray diffraction (powder method) and Raman spectroscopy.
Blackhead Quarry exploits a small Miocene (~10 Ma) basanitic volcanic centre in the Dunedin Volcanic Group, New Zealand. Vesicles near the quarry top contain Ca– and Na-rich zeolites, abundant calcite and rare pyrite resulting from localized low-T hydrothermal alteration (<100°C). Mineral assemblages were characterized by EDS and laser Raman spectroscopy with the latter the most useful in determining the identity of fibrous zeolite species. Secondary mineral assemblages crystallized during final stages of lava cooling from aqueous solutions enriched in Ca, Na, K, Ba and (CO3)2–leached from surrounding calcareous rocks and basanite. Phillipsite-K (generation I) crystallized first (in some places directly on fresh basanite) followed by the Ca-rich zeolites, chabazite-Ca, calcian phillipsite–K (generation II), gismondine and thomsonite. Later Na-rich fluids crystallized gonnardite and natrolite, and finally calcite from late Ca-rich fluids. Zeolite composition is not reflected by morphology. For example, both phacolitic and pseudocubic chabazite are chabazite-Ca, and although all phillipsite crystals have a similar habit, their composition varies widely. Various lithologies comprising the Blackhead volcanic centre have unique secondary mineral paragenetic sequences controlled largely by the rock structure and solution chemistry.
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