We present a synthesis of some 20,504 mineral analyses of ~500 Hole 735B gabbros, including 10,236 new analyses conducted for this paper. These are used to construct a mineral stratigraphy for 1.5-km-deep Hole 735B, the only long section of the lower crust drilled in situ in the oceans. At long wavelengths, generally >200 m, there is a good chemical correlation among the principal silicate phases, consistent with the in situ crystallization of three or four distinct olivine gabbro bodies, representing at least two major cycles of intrusion. Initial cooling and crystallization of these bodies must have been fairly rapid to form a crystal mush, followed by subsequent compaction and migration of late iron-titanium-rich liquids into shear zones and fractures through which they were emplaced to higher levels in the lower crust where they crystallized and reacted with the olivine gabbro host rock to form a wide variety of ferrogabbros. At the wave lengths of the individual intrusions, as represented by the several olivine gabbro sequences, there is a general upward trend of iron and sodium enrichment but a poor correlation between the compositions of the major silicate phases. This, together with a wide range in minor incompatible and compatible element concentrations in olivine and pyroxene at a given Mg#, is con-., 2002.Primary silicate mineral chemistry of a 1.5-km section of very slow spreading lower ocean crust: ODP Hole 735B, Southwest Indian Ridge. In Natland, H.J.B. DICK ET AL. PRIMARY SILICATE MINERAL CHEMISTRY 2 sistent with widespread permeable flow of late melt through these intrusions, in contrast to what has been documented for a 600-m section of reputedly fast-spreading ocean crust in the Oman Ophiolite. This unexpected finding could be related to enhanced compaction and deformation-controlled late-stage melt migration at the scale of intrusion at a slow-spreading ocean ridge, compared to the relatively static environment in the lower crust at fast-spreading ridges. H.J.B. DICK ET AL. PRIMARY SILICATE MINERAL CHEMISTRY 3basis of clear textural and mineralogic differences. This breakdown did not generally include intervals of less than ~4 cm, and further subdivision of the core could be made. With the analytical data set estimated to represent ~500 discrete samples, it remains inadequate to describe the core in anywhere near its entirety. ANALYTICAL METHODSThe data sets reported in Tables T1, T2, T3, T4, and T5, other than those collected by the first author and his colleagues at Massachusetts Institute of Technology (MIT), were collected by investigators using different analytical schemes, techniques, and standards. They describe these in papers in the Leg 118 and Leg 176 volumes Hebert et al., 1991;Natland et al., 1991; Niu et al., Chap. 8, this volume;Ozawa et al., 1991; Robinson et al., Chap. 9, this volume). The new data collected at the MIT Electron Microprobe Facility used a JEOL JXA-733 Superprobe. The operating conditions included a 15-keV accelerating voltage, 10-nA probe current, 10-µm spot si...

Mineral carbonation of ultramafic rocks provides an environmentally safe and permanent solution for CO(2) sequestration. In order to assess the carbonation potential of ultramafic waste material produced by industrial processing, we designed a laboratory-scale method, using a modified eudiometer, to measure continuous CO(2) consumption in samples at atmospheric pressure and near ambient temperature. The eudiometer allows monitoring the CO(2) partial pressure during mineral carbonation reactions. The maximum amount of carbonation and the reaction rate of different samples were measured in a range of experimental conditions: humidity from dry to submerged, temperatures of 21 and 33 °C, and the proportion of CO(2) in the air from 4.4 to 33.6 mol %. The most reactive samples contained ca. 8 wt % CO(2) after carbonation. The modal proportion of brucite in the mining residue is the main parameter determining maximum storage capacity of CO(2). The reaction rate depends primarily on the proportion of CO(2) in the gas mixture and secondarily on parameters controlling the diffusion of CO(2) in the sample, such as relative saturation of water in pore space. Nesquehonite was the dominant carbonate for reactions at 21 °C, whereas dypingite was most common at 33 °C.

New U-Pb zircon ages from nine samples of igneous and sedimentary rocks in the Aspy terrane, Cape Breton Island, show that Neoproterozoic rocks form a major part of the terrane and confirm that the terrane was affected by a major Silurian-Devonian tectonothermal event. A rhyolitic crystal tuff, a leucotonalite pluton and a felsic sheet yield ages of 618.8 ؎ 0.6 Ma, 619.7 ؎ 0.9 Ma and 573.5 ؎ 2.7 Ma, respectively. A metasedimentary unit contains zircon ranging in age from ca. 546 to ca. 1520 Ma. A diorite has an age of 428.6 ؎ 1.9 Ma, and another diorite unit and a quartz porphyry also have probable Late Silurian ages. A third diorite yields an age of 373.0 ؎ 0.5 Ma, part of a widespread bimodal igneous event represented by both volcanic and plutonic rocks throughout the Aspy region. Geochronological results and field relationships indicate that the Neoproterozoic rocks are similar to those in the Bras d'Or terrane and form the basement to the (Ordovician-)Silurian rocks in the Aspy terrane, and that the Aspy terrane is probably correlative with rocks in the Hermitage flexure of southern Newfoundland where Silurian metasedimentary and metavolcanic rocks lie unconformably on similar Neoproterozoic rocks. Likely correlative rocks also occur in the Kingston terrane of southern New Brunswick. The results of this study support the idea that the Aspy-Kingston terrane is part of Ganderia and that Neoproterozoic rocks in the Bras d'Or terrane and correlative rocks in southwestern Newfoundland and elsewhere represent exposed basement to Ganderia in the Canadian Appalachians.

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