Secondary Minerals in Some Basaltic Rocks from Deep Sea Drilling Project Legs 52 and 53, Hole 418A

Scarfe, Christopher M.

doi:10.2973/dsdp.proc.515253.149.1980

Cited by 5 publications

(6 citation statements)

References 13 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The white (K-Al-Si)-rich devitrified zones described here are similar in size, shape, geological context, and chemical composition to light coloured K-rich zones documented in a previous study of DSDP 418A basaltic glasses [186], where they were also found to occur in basaltic glass along some fractures and as rims around some plagioclase phenocrysts and interpreted as poorly crystalline, secondary K-feldspar.…”

Section: White (K-supporting

confidence: 78%

Discovery of Naturally Etched Fission Tracks and Alpha-Recoil Tracks in Submarine Glasses: Reevaluation of a Putative Biosignature for Earth and Mars

French

Blake

2016

International Journal of Geophysics

View full text Add to dashboard Cite

Over the last two decades, conspicuously “biogenic-looking” corrosion microtextures have been found to occur globally within volcanic glass of thein situoceanic crust, ophiolites, and greenstone belts dating back to ~3.5 Ga. These so-called “tubular” and “granular” microtextures are widely interpreted to representbona fidemicrobial trace fossils; however, possible nonbiological origins for these complex alteration microtextures have yet to be explored. Here, we reevaluate the origin of these enigmatic microtextures from a strictly nonbiological standpoint, using a case study on submarine glasses from the western North Atlantic Ocean (DSDP 418A). By combining petrographic and SEM observations of corrosion microtextures at the glass-palagonite interface, considerations of the tectonic setting, measurement of U and Th concentrations of fresh basaltic glass by ICP-MS, and theoretical modelling of the present-day distribution of radiation damage in basaltic glass caused by radioactive decay of U and Th, we reinterpret these enigmatic microtextures as the end product of the preferential corrosion/dissolution of radiation damage (alpha-recoil tracks and fission tracks) in the glass by seawater, possibly combined with pressure solution etch-tunnelling. Our findings have important implications for geomicrobiology, astrobiological exploration of Mars, and understanding of the long-term breakdown of nuclear waste glass.

show abstract

Section: White (K-supporting

confidence: 78%

Discovery of Naturally Etched Fission Tracks and Alpha-Recoil Tracks in Submarine Glasses: Reevaluation of a Putative Biosignature for Earth and Mars

French

Blake

2016

International Journal of Geophysics

View full text Add to dashboard Cite

show abstract

“…Oxidative alteration by both cold seawater processes and hydrothermal circulation decreases dramatically with increasing depth in the upper 70 m of Site 597 basement. The relatively shallow zone of intense alteration contrasts with the much deeper zone of low-temperature alteration at DSDP Sites 332B and 418A (Scarfe, 1980); the contrast reflects the low porosity and permeability of the Site 597 massive seafloor basalts. In addition, a zone of oxidative alteration became shallower with time as the precipitation of secondary minerals filled available fracture spaces.…”

Section: K-ar Dating Of Celadonite In Fracture Fillings In Site 597 Bmentioning

confidence: 91%

Sequence and Longevity of Basalt Alteration at Deep Sea Drilling Project Site 597

Peterson¹,

Duncan²,

Scheidegger³

1986

Initial Reports of the Deep Sea Drilling Project

View full text Add to dashboard Cite

Preliminary studies of hydrothermally altered massive basalts formed at the fast-spreading Mendoza Rise and recovered from DSDP Holes 597B and 597C indicate the presence of three secondary mineral assemblages which formed in the following order: (1) trioctahedral chlorite and talc, (2) goethite and smectite, and (3) calcite and celadonite. The sequential precipitation of these mineral assemblages denotes high wateπrock ratios and time-varying conditions of temperature (early >200°C to late <30°C) and state of oxidation (early nonoxidative to late oxidative). A decrease in the relative proportion of oxidative mineral assemblages with depth to 70 m in Site 597 basement indicates a zone of oxidative alteration that became shallower with time as the deeper, more constricted fracture systems were filled by secondary mineralization. In this report we present the first results of the K-Ar dating of celadonite formation age; celadonite formation reflects end-stage hydrothermal alteration in Site 597 basement. Three celadonite dates obtained from Site 597 samples include 13.1 ± 0.3 m.y. from 17 m basement depth (Hole 597B), 19.9 ± 0.4 m.y. from 18 m basement depth (Hole 597C), and 19.3 ± 1.6 m.y. from 60 m basement depth (Hole 597C). The age of host rock crystallization (28.6 m.y.) and the K-Ar dates of celadonite formation establish that hydrothermal alteration in the upper 70 m of Site 597 basement continued for at least 10 m.y. and possibly as long as 16 m.y. after basalt crystallization at the ridge crest. Assuming a half-spreading rate of 55 km/m.y., we calculate that hydrothermal circulation was active in shallow basement at a distance of at least 550 km off ridge crest and possibly as far as 1000 km off ridge crest.

show abstract

“…Oxygen-isotope analyses indicate that alteration occurred under low-temperature conditions. Scarfe (1980) reported 5 8 0 values of 17.1%o and 18.1%o in two clay samples from Hole 418A, which are indicative of low temperatures of formation. Isotopic analyses of basalts, carbonates, and a clay by Muehlenbachs (1980) indicate that basalts are enriched in 18 0 during alteration by cold seawater.…”

Section: General Descriptionmentioning

confidence: 95%

“…Abundance in weight percent. Sample Humphris et al (1980) 33-2, 124 cm 52-4, 75-80 cm 52-4, 75-80 cm 30-3, 35-38 cm 30-3, 35-38 cm 52-4, 75-80 cm 52-4, 75-80 cm 52-4, 75-80 cm 60-1, 117-121 cm 60-1, 117-121 cm Mevel (1980) 38-3, 4-6 cm 38-3, 31-33 cm 38-3, 50-52 cm 42-2, 138-143 cm 59-4, 134-110 cm 74-2, 69-71 cm 86-2, 91-94 cm Scarfe (1980) 55-2, 48-50 cm Average, green clays Humphris et al (1980) 19-5, 42-46 cm 52-4, 75-80 cm 71-3, 101-104 cm 71-3, 101-104 cm 30-3, 35-38 cm 30-3, 35-38 cm 30-3, 35-38 cm 52-4, 75-80 cm 60-1, 117-121 cm Mevel (1980) 38-3, 50-52 cm 42-2, 138-143 cm 42-2, 138-143 cm 56-6, 56-60 cm 59-4, 134-140 cm 86-2, 91-94 cm Scarfe (1980) were observed under a Cambridge SEM equipped with a Princeton Gamma-Tech EDS for standardless spectral analyses.…”

Section: Current Studymentioning

confidence: 99%

Evidence for Continuous and Discontinuous Alteration in DSDP Hole 418A Basalts and its Significance to Natural Gamma-Ray Log Readings

Holmes¹

1988

Proceedings of the Ocean Drilling Program

View full text Add to dashboard Cite

During Ocean Drilling Program Leg 102, the Schlumberger natural gamma-ray spectrometry tool measured high potassium levels in one interval of DSDP Hole 418A basalts. Samples from that hole were examined by X-ray diffraction, SEM, and EDS analyses in order to identify mineral species responsible for the high readings. The results indicate that high K readings observed on wireline logs run in basement can be attributed to extensive low-temperature oxidative alteration resulting in formation of palagonite and K-rich clays (celadonite, potassic nontronite, and mixed-layer celadonite/nontronite). Where these readings are accompanied by high porosity, low density, and low velocity readings, a breccia with a once-glassy matrix, now altered to K-rich clay, may be inferred. Where porosity, density, and velocity readings indicate no breccia, high K readings may be attributed to potassium feldspar, an indicator of a second stage of oxidative alteration. In either case, there is a significant contribution to the K readings from palagonite. Further results of this study indicate a continuous fluid evolution and secondary mineral formation in these basalts. An initial stage of oxidation and formation of iron oxide-hydroxides was followed by precipitation of K-rich clay minerals. The first clays to form may have been celadonite, mixed-layer celadonite/nontronite, or potassic nontronite. As the fluid evolved, the minerals formed were increasingly depleted in K and ferric iron and increasingly enriched in Mg, Al, Ca, and ferrous iron. The final phase was an iron-rich saponite. In at least one interval with high permeability, a second stage of oxidative alteration resulting from the influx of a new fluid is demonstrated by the alteration of saponite to iddingsite (saponite + goethite). Potassium feldspar is associated with this zone and is believed to have formed with the second stage of oxidative alteration.

show abstract

Secondary Minerals in Some Basaltic Rocks from Deep Sea Drilling Project Legs 52 and 53, Hole 418A

Cited by 5 publications

References 13 publications

Discovery of Naturally Etched Fission Tracks and Alpha-Recoil Tracks in Submarine Glasses: Reevaluation of a Putative Biosignature for Earth and Mars

Discovery of Naturally Etched Fission Tracks and Alpha-Recoil Tracks in Submarine Glasses: Reevaluation of a Putative Biosignature for Earth and Mars

Sequence and Longevity of Basalt Alteration at Deep Sea Drilling Project Site 597

Evidence for Continuous and Discontinuous Alteration in DSDP Hole 418A Basalts and its Significance to Natural Gamma-Ray Log Readings

Contact Info

Product

Resources

About