(Table T2) Integrated intensity (peak area) of matrix minerals of ODP Hole 173-1068A

Mass-wasting deposits characterize the Upper Jurassic(?) to Lower Cretaceous sedimentary record of the Iberia Abyssal Plain. These deposits include olistostromes at Site 897, olistostromes and/or possible rock-fall deposits at Site 899, a breccia succession at Site 1068, slumped and fractured deposits at Site 1069, and a breccia succession at Site 1070. Whereas the exact origin of these deposits is uncertain, the regional common occurrence of middle to upper Mesozoic mass-wasting deposits suggests that they record the early rifting evolution of the west Iberia margin. This data report presents both qualitative and semiquantitative results from XRD analyses of the breccia matrix at Site 1068. In this study the matrix is defined as the fine-grained particles (as viewed through a binocular microscope) plus cement. Results are based on analytical methods that aimed to isolate the desired matrix from larger clast contamination prior to XRD analyses. In addition, the breccia was sampled at a higher resolution than was conducted aboard ship, producing a more complete description of downcore matrix mineralogical changes. The data presented here may be used to (1) further justify the subunit designation of Unit IV made aboard ship, (2) help determine to what degree the matrix and the larger clasts (studied in thin section aboard ship; Shipboard Scientific Party, 1998, doi:10.2973/odp.proc.ir.173.106.1998) are compositionally distinct, (3) help identify the extent of hydrothermal fluid migration in the breccia, and (4) support the proposed shipboard hypothesis that the Site 1068 breccia succession resulted from multiple mass-wasting.

(Table 1) Peak intensity of minerals in ODP Hole 126-793B

Sediments and rocks recovered during Ocean Drilling Program Leg 126 at Sites 792 and 793 in the Izu-Bonin forearc basin are described with a primary focus on clay mineralogy. Evidence for diagenetic hydrothermal alteration processes is present in the upper Oligocene to lower Miocene sediments at these sites. The vitric and pumiceous sand/sandstone and pumiceous gravel contain high concentrations of smectites, zeolites, and gypsum. Microscopic observations show that the volcanic glass and feldspars have been altered to smectites and zeolites. The authigenic mineral assemblages indicate that these minerals resulted from precipitation from circulating fluids, as well as from the alteration of glass and feldspar under temperature conditions that may have reached 200°-300°C. Mineral assemblages in microfractures display thermal gradients that possibly reflect cooling effects.

Evolução diagenética e caracterização dos reservatórios da seção devoniana na Bacia do Rio do Peixe-Nordeste do Brasil

The Rio do Peixe Basin represents a main basin of northeastern Brazil and pioneering work positioned the rocks of this basin in the Early Cretaceous. However, a recent study, based on integrated pollen analysis from three wells, found an unprecedented siliciclastic sedimentary section, in the region, of early Devonian age. Therefore, the present study aims a detailed petrographic and petrological analysis of this devonian section, in the Rio do Peixe Basin and proposes a diagenetic evolution, to understand the characteristics of the porous system, identify the main reservoir petrofacies with the main factors impacting on the quality of these rocks as reservoirs and a quick study on the provenance of this section. The petrographic study was based on samples obtained from subsurface and surface. The diagenetic evolution of petrofacies and its identification were based only on subsurface samples and the study of provenance was based on surface samples. The thin sections were prepared from sandstones, pelites and sandstones intercalated with pelites. The original detrital composition for this section is arcosean and the main diagenetic processes that affected these rocks occur in various depths and different conditions, which resulted in extensive diagenetic variety. The following processes were identified: early fracture and healing of grains; albitization of K-feldspar and plagioclase; siderite; precipitation of silica and feldspar; mechanical infiltration of clay and its transformation to illite/esmectite and illite; autigenesis of analcime; dissolution; autigenesis of chlorite; dolomite/ferrous dolomite/anquerite; apatite; calcite; pyrite; titanium minerals and iron oxide-hidroxide. The occurrence of a recently discovered volcanism, in the Rio do Peixe Basin, may have influenced the diagenetic evolution of this section. Three diagenetic stages affected the Devonian section: eo, meso and telodiagenesis. This section is compositionally quite feldspathic, indicating provenance from continental blocks, between transitional continental and uplift of the basement. From this study, we observed a wide heterogeneity in the role of the studied sandstones as reservoirs. Seven petrofacies were identified, taking into account the main diagenetic constituent responsible for the reduction of porosity. It is possible that the loss of original porosity was influenced by intense diagenesis in these rocks, where the main constituent for the loss of porosity are clays minerals, oxides and carbonate cement (calcite and dolomite)