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Petrology and geochemistry of basalt at DSDP Hole 66-487
No full textMajor oxide and trace element determinations of the composition basalts from the bottom of Hole 487, together with microprobe analyses of their minerals (olivine, magnesiochromite, salite, and plagioclase), prove that they are depleted oceanic tholeiites
Resolución UNRN N° 487/2009. Contratar personal temporario.
No full textFil: Universidad Nacional de Río Negro (U). Universidad Nacional de Río Negro. Río Negro, ArgentinaResolución UNRN N° 487/2009. Contratar personal temporario.fals
(Table 1) Geochemistry of Cocos Plate hemipelagic-pelagic sediments in DSDP Hole 66-487
No full textThe sedimentary sequence recovered from Hole 487 documents northeast seafloor spreading on the Cocos Plate. A basal 65-meter unit of upper Miocene-Pliocene brown clay was deposited on the subsiding east flank of the East Pacific Rise. The overlying 105-meter unit of gray hemipelagic silt and mud was deposited when Site 487 drifted within reach of terrigenous sediment derived from the Mexican continental margin.
Analyses of 21 elements in 45 samples, taken at regular intervals up Hole 487, give a geochemical profile which shows metal enrichment in basal sediment similar to that observed in previously recovered basal sediment sections in the Eastern Pacific (e.g., von der Borch & Rex, 1970; von der Borch et al., 1971). This verifies that the basalt cored at the base the hole is oceanic basement, since the first sediment to be deposited on newly formed ocean crust is characteristically enriched in metals, particularly Fe and Mn. The metals precipitate from circulating hydrothermal-exhalative solutions which are an integral part of active ridge volcanism (summary in Jenkyns, 1978). In this chapter I discuss the geochemistry of the basal metalliferous sediment from Hole 487.
The geochemical data may also prove useful in studies of onshore volcanism: mass-balance calculations show that much (possibly all) of the incoming Cocos Plate sediment has been subducted since the Miocene (Watkins et al., this volume). It may have contributed to the genesis of magmas erupted in the Mexican volcanic ar
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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