Boron contents of serpentinites and metabasalts in the oceanic crust: Implications for the boron cycle in the oceans
TL;DR: Boron is preferentially partitioned into the liquid phase in high-temperature reactions of basaltic rocks and sea-water as mentioned in this paper, and it is used to prevent peridotite serpentinization.
About: This article is published in Earth and Planetary Science Letters.The article was published on 1970-03-01. It has received 100 citations till now. The article focuses on the topics: Oceanic crust & Boron.
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TL;DR: In this paper, samples collected by the deep submersible Alvin from four hot spring fields (T = 3 − 13°C) on the crest of the Galapagos spreading ridge show pronounced and varied compositional anomalies.
897 citations
TL;DR: Basalts cored on legs 2 and 3 of the Deep-Sea Drilling Project (DSDP) range in sea floor spreading age from 18 to 67×106 yr as discussed by the authors.
Abstract: Basalts cored on legs 2 and 3 of the Deep-Sea Drilling Project (DSDP) range in sea floor spreading age from 18 to 67×106 yr. Although many of the basalts are highly altered, fresh glass is usually present. Except for site 2–10 the fresh glasses are petrographically and geochemically similar to mid-Atlantic ridge (MAR) axial basalts. There are no systematic compositional differences as a function of distance from the MAR axis. Two sites contain basalts with olivine (Fo90) phenocrysts, high Mg/Mg + ΣFe, high Ni and Cr abundances, and very low large ion lithophile (LIL) element abundances. These basalts are the best candidates for primary magma recovered from the sea floor; fractional crystallization of such basalt may yield the more evolved basalts typical of the MAR. More fractionated basalts with clinopyroxene phenocrysts occur at twp other sites, but they retain low LIL element abundances. Site 2-10 contains titaniferous augite and is relatively enriched in LIL elements. It is unlikely that this basalt was derived by fractional crystallization from LIL element depleted tholeiites; instead, the site 2-10 basalt requires a different mantle source. These results imply that the upper Atlantic Ocean basement is dominantly LIL element depleted tholeiite.
549 citations
TL;DR: In this article, a large scale boron exchange between seawater and the oceanic crust has been demonstrated at both high and low temperature, and the B content of altered whole rocks correlates strongly with δ18O, and increases with degree of alteration.
531 citations
TL;DR: In this paper, the authors propose a method for the detection of asteroids in the Earth and Planetary Sciences (EPSS) domain. Ph.D., Massachusetts Institute of Technology.
510 citations
Cites background from "Boron contents of serpentinites and..."
...Previous studies of boron in oceanic basalts (Thompson and Melson, 1970) suggested that low temperature weathering, at ambient bottom water temperatures, resulted in uptake of boron, but that hydrothermally altered basalts may be depleted in this...
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TL;DR: A review of the geochemistry of serpentinites, based on the compilation of ~900 geochemical data of abyssal, mantle wedge and exhumed serpentinite after subduction, is presented in this paper.
499 citations
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TL;DR: For example, this article showed that the amount of CO 2 in the atmosphere and ocean has remained relatively constant throughout much of the geologic past, and that it is likely that only a small fraction of the total volume of volatiles was ever present at one time in the early atmosphere and oceans.
Abstract: Paleontology and biochemistry together may yield fairly definite information, eventually, about the paleochemistry of sea water and atmosphere. Several less conclusive lines of evidence now available suggest that the composition of both sea water and atmosphere may have varied somewhat during the past; but the geologic record indicates that these variations have probably been within relatively narrow limits. A primary problem is how conditions could have remained so nearly constant for so long. It is clear, even from inadequate data on the quantities and compositions of ancient sediments, that the more volatile materials—H 2 O, CO 2 , Cl, N, and S— are much too abundant in the present atmosphere, hydrosphere, and biosphere and in ancient sediments to be explained, like the commoner rock-forming oxides, as the products of rock weathering alone. If the earth were once entirely gaseous or molten, these “excess” volatiles may be residual from a primitive atmosphere. But if so, certain corollaries should follow about the quantity of water dissolved in the molten earth and the expected chemical effects of a highly acid, primitive ocean. These corollaries appear to be contradicted by the geologic record, and doubt is therefore cast on this hypothesis of a dense primitive atmosphere. It seems more probable that only a small fraction of the total “excess” volatiles was ever present at one time in the early atmosphere and ocean. Carbon plays a significant part in the chemistry of sea water and in the realm of living matter. The amount now buried as carbonates and organic carbon in sedimentary rocks is about 600 times as great as that in today9s atmosphere, hydrosphere, and biosphere. If only 1/100 of this buried carbon were suddenly added to the present atmosphere and ocean, many species of marine organisms would probably be exterminated. Furthermore, unless CO 2 is being added continuously to the atmosphere-ocean system from some source other than rock weathering, the present rate of its subtraction by sedimentation would, in only a few million years, cause brucite to take the place of calcite as a common marine sediment. Apparently, the geologic record shows no evidence of such simultaneous extinctions of many species nor such deposits of brucite. Evidently the amount of CO 2 in the atmosphere and ocean has remained relatively constant throughout much of the geologic past. This calls for some source of gradual and continuous supply, over and above that from rock weathering and from the metamorphism of older sedimentary rocks. A clue to this source is afforded by the relative amounts of the different “excess” volatiles. These are similar to the relative amounts of the same materials in gases escaping from volcanoes, fumaroles, and hot springs and in gases occluded in igneous rocks. Conceivably, therefore, the hydrosphere and atmosphere may have come almost entirely from such plutonic gases. During the crystallization of magmas, volatiles such as H 2 O and CO 2 accumulate in the remaining melt and are largely expelled as part of the final fractions. Volcanic eruptions and lava flows have brought volatiles to the earth9s surface throughout the geologic past; but intrusive rocks are probably a much more adequate source of the constituents of the atmosphere and hydrosphere. Judged by the thermal springs of the United States, hot springs (carrying only 1 per cent or less of juvenile matter) may be the principal channels by which the “excess” volatiles have escaped from cooling magmas below. This mechanism fails to account for a continuous supply of volatiles unless it also provides for a continuous generation of new, volatile-rich magmas. Possibly such local magmas form by a continuous process of selective fusion of subcrustal rocks, to a depth of several hundred kilometers below the more mobile areas of the crust. This would imply that the volume of the ocean has grown with time. On this point, geologic evidence permits differences of interpretation; the record admittedly does not prove, but it seems consistent with, an increasing growth of the continental masses and a progressive sinking of oceanic basins. Perhaps something like the following mechanism could account for a continuous escape of volatiles to the earth9s surface and a relatively uniform composition of sea water through much of geologic time: (1) selective fusion of lower-melting fractions from deep-seated, nearly anhydrous rocks beneath the unstable continental margins and geosynclines; (2) rise of these selected fractions (as granitic and hydrous magmas) and their slow crystallization nearer the surface; (3) essentially continuous isostatic readjustment between the differentiating continental masses and adjacent ocean basins; and (4) renewed erosion and sedimentation, with resulting instability of continental margins and mountainous areas and a new round of selective fusion below.
590 citations
TL;DR: In this paper, a series of U.S. Geological Survey (USGS) rock samples were used for determining major and minor constituents and 57 trace elements reported by analysts throughout the world.
421 citations
TL;DR: In this article, an analysis of waters from many New Zealand hydrothermal areas (both volcanic and non-volcanic) is presented for discussion, and the natural hot-water compositions are compared with those resulting from the experimental interaction of water at 150-350°C with volcanic rocks and a greywacke from the central part of the North Island of New Zealand.
412 citations
TL;DR: In this article, the authors show that the trend of decreasing K/Rb with increasing K content is a probable result of later alteration, both during low grade metamorphism and during exchange with sea water.
249 citations
TL;DR: The petrology of the mid-Atlantic ridge between 22° and 23°N latitude may be typical of those portions of the ridge characterized by a linear topography parallel to the axis, a well-developed median valley, and an absence of volcanic cones.
Abstract: The petrology of the mid-Atlantic ridge between 22° and 23°N latitude may be typical of those portions of the ridge characterized by a linear topography parallel to the axis, a well-developed median valley, and an absence of volcanic cones. Submarine basalt lavas dredged at fifteen stations on the crest of the ridge are of three eruptive facies, all derived from essentially identical magmas; (1) pillow lavas, (2) sideromelane-rich tuffs, and (3) massive, mainly holocrystalline basalts. This association is well known from continental exposures of ancient submarine lavas. Chemically, the lavas are oceanic tholeiites and thus support the view that these low-potassium olivine basalts are by far the dominant eruptive on the deep-sea floor. In the 22° area, they are probably the product of voluminous fissure eruptions. The oceanic tholeiite is evidently the counterpart of the continental flood basalts, but it differs compositionally from these, especially in a lower potassium content. As a further characterization of the basalts, seven new analyses of major, minor, and trace elements are presented. Post-cooling hydrothermal metamorphism under some overburden has transformed some of these basalts into greenschists and lower-grade metamorphic rocks. New data indicate that faulting and shearing along the median valley combined with the introduction of hot, probably saline solutions were major agents in the metamorphism.
240 citations