Tertiary basalts of western Davis Strait: bedrock core samples and geophysical data

1978 ◽  
Vol 15 (5) ◽  
pp. 773-780 ◽  
Author(s):  
B. MacLean ◽  
R. K. H. Falconer ◽  
D. B. Clarke
Keyword(s):  
Magnetic Anomaly ◽  
Seismic Reflection ◽  
Volcanic Rocks ◽  
Geophysical Data ◽  
Baffin Island ◽  
Main Area ◽  
Fine Grained ◽  
Core Samples ◽  
Davis Strait ◽  
Island Shelf

Short bedrock cores of basalt were recovered at two localities on the Baffin Island shelf, 33 and 89 km southeast of Cape Dyer. The volcanic rocks underlying these sites have a surface extent of some 8000 km2 as outlined by seismic reflection and magnetic anomaly profiles. Similar rocks are inferred to occur at two smaller offshore areas south of the main area. The offshore occurrences are both more continuous and much larger than the onshore basalt areas of eastern Baffin Island.The core samples appear to have been cut from single flows consisting of fine-grained microporphyritic basalts with olivine as the principal phenocryst phase. Although having distinct differences from one another in terms of texture and degree of alteration, the samples from the three drill stations bear similarities to the Baffin Island basalts that suggest a close petrogenetic relationship may exist between the onshore and offshore basalts. However, in contrast to the subaqueously erupted volcanic breccias of onshore Baffin Island and West Greenland the offshore samples contain little evidence of glass, suggesting the possibility that the latter may have been erupted in a subaerial environment.

Early Tertiary basalts from the Labrador Sea floor and Davis Strait region

1989 ◽  
Vol 26 (5) ◽  
pp. 956-968 ◽  
Author(s):  
D. B. Clarke ◽  
B. I. Cameron ◽  
G. K. Muecke ◽  
J. L. Bates
Keyword(s):  
Volcanic Rocks ◽  
Labrador Sea ◽  
Baffin Island ◽  
Nd Isotope ◽  
Sea Floor ◽  
West Greenland ◽  
Depleted Mantle ◽  
Davis Strait ◽  
Isotope Systematics ◽  
Seawater Exchange

Fine- to medium-grained, phyric and aphyric basalt samples from ODP Leg 105, site 647A, in the Labrador Sea show little evidence of alteration. Chemically, these rocks are low-potassium (0.01–0.09 wt.% K2O), olivine- to quartz-normative tholeiites that compare closely with the very depleted terrestrial Paleocene volcanic rocks in the Davis Strait region of Baffin Island and West Greenland. However, differences exist in the Sr–Nd isotope systematics of the two suites; the Labrador Sea samples have ε Nd values (+9.3) indicative of a more depleted source, and are higher in 87Sr/86Sr (0.7040), relative to the Davis Strait basalts (ε Nd +2.54 to +8.97; mean 87Sr/86Sr 0.7034). The higher 87Sr/86Sr in the Labrador Sea samples may reflect seawater exchange despite no petrographic evidence for significant alteration. The Labrador Sea and early Davis Strait basalts may have been derived from a similar depleted mantle source composition; however, the later Davis Strait magmas were generated from a different mantle. None of the Baffin Island, West Greenland, or Labrador Sea samples show unequivocal geochemical evidence for contamination with continental crust.

scholarly journals Volume, Freshwater, and Heat Fluxes through Davis Strait, 2004–05*

2011 ◽  
Vol 41 (3) ◽  
pp. 429-436 ◽  
Author(s):  
B. Curry ◽  
C. M. Lee ◽  
B. Petrie
Keyword(s):  
Heat Fluxes ◽  
First Year ◽  
Baffin Island ◽  
Fram Strait ◽  
The West ◽  
Baffin Bay ◽  
Freshwater Fluxes ◽  
Davis Strait ◽  
Island Shelf ◽  
Southward Transport

Abstract Davis Strait volume [−2.3 ± 0.7 Sv (1 Sv ≡ 106 m3 s−1); negative sign indicates southward transport], freshwater (−116 ± 41 mSv), and heat (20 ± 9 TW) fluxes estimated from objectively mapped 2004–05 moored array data do not differ significantly from values based on a 1987–90 array but are distributed differently across the strait. The 2004–05 array provided the first year-long measurements in the upper 100 m and over the shelves. The upper 100 m accounts for 39% (−0.9 Sv) of the net volume and 59% (−69 mSv) of the net freshwater fluxes. Shelf contributions are small: 0.4 Sv (volume), 15 mSv (freshwater), and 3 TW (heat) from the West Greenland shelf and −0.1 Sv, −7 mSv, and 1 TW from the Baffin Island shelf. Contemporaneous measurements of the Baffin Bay inflows and outflows indicate that volume and freshwater budgets balance to within 26% and 4%, respectively, of the net Davis Strait outflow. Davis Strait volume and freshwater fluxes nearly equal those from Fram Strait, indicating that both are significant Arctic freshwater pathways.

Depleted and ultradepleted basalt and picrite in the Davis Strait: Paleocene volcanism associated with a transform continental margin

2020 ◽  
Vol 157 (12) ◽  
pp. 1983-2003 ◽  
Author(s):  
Lotte Melchior Larsen ◽  
Marie-Claude Williamson
Keyword(s):  
Volcanic Rocks ◽  
Spinel Peridotite ◽  
Baffin Island ◽  
Nd Isotopes ◽  
Enriched Mantle ◽  
Spreading Ridges ◽  
Magmatic Underplating ◽  
Davis Strait ◽  
Melting Regime ◽  
Transform Zone

AbstractVolcanic rocks from the Davis Strait were studied to elucidate the tectonomagmatic processes during rifting and the start of seafloor spreading, and the formation of the Ungava transform zone between Canada and Greenland. The rocks are from the wells Hekja O-71, Gjoa G-37, Nukik-2 and Hellefisk-1, and from dredges on the northern Davis Strait High. Ages range from Danian to Thanetian (dinocyst palynozones P2 to P5, 62.5–57.2 Ma). The rocks are predominantly basaltic, but include picrites on the Davis Strait High. Calculated mantle potential temperatures for the Davis Strait High are c. 1500°C, suggesting the volume of magma generated was large; this is consistent with geophysical evidence for magmatic underplating in the region. The rare earth element patterns indicate residual mantle lithologies of spinel peridotite and, together with Sr–Nd isotopes, indicate melting beneath regionally extensive, depleted asthenosphere beneath a lithosphere of thickness similar to, or thinner than, beneath Baffin Island and distinctly thinner than beneath West Greenland. Some sites include basalts with more enriched compositions. Depleted and enriched basalts in the Hellefisk well show contemporaneous melting of depleted and enriched mantle components in the asthenosphere. The Hekja and Davis Strait High basalts and picrites have unique, ultradepleted compositions with (La/Sm)N < 0.5, (Tb/Lu)N < 1 and Nb/Zr = 0.013–0.027. We interpret these compositions as a product of the melting regime within the Ungava transform zone, where the melting column would be steep-sided in cross-section and not triangular as expected at normal spreading ridges. Magmatism along the transform stopped when the tectonic regime changed from transtension to transpression during earliest Eocene time.

TEM/AEM characterization of fine-grained clay minerals in very-low-grade rocks: Evaluation of contamination by empa involving celadonite family minerals

1996 ◽  
Vol 54 ◽  
pp. 694-695
Author(s):  
Gejing Li ◽  
D. R. Peacor ◽  
D. S. Coombs ◽  
Y. Kawachi
Keyword(s):  
Electron Microscopy ◽  
Volcanic Rocks ◽  
Analytical Electron Microscopy ◽  
Metamorphic Rocks ◽  
New Mineral ◽  
Chemical Compositions ◽  
Low Grade ◽  
Fine Grained ◽  
Depth Analysis ◽  
Mineral Aggregates

Recent advances in transmission electron microscopy (TEM) and analytical electron microscopy (AEM) have led to many new insights into the structural and chemical characteristics of very finegrained, optically homogeneous mineral aggregates in sedimentary and very low-grade metamorphic rocks. Chemical compositions obtained by electron microprobe analysis (EMPA) on such materials have been shown by TEM/AEM to result from beam overlap on contaminant phases on a scale below resolution of EMPA, which in turn can lead to errors in interpretation and determination of formation conditions. Here we present an in-depth analysis of the relation between AEM and EMPA data, which leads also to the definition of new mineral phases, and demonstrate the resolution power of AEM relative to EMPA in investigations of very fine-grained mineral aggregates in sedimentary and very low-grade metamorphic rocks.Celadonite, having end-member composition KMgFe3+Si4O10(OH)2, and with minor substitution of Fe2+ for Mg and Al for Fe3+ on octahedral sites, is a fine-grained mica widespread in volcanic rocks and volcaniclastic sediments which have undergone low-temperature alteration in the oceanic crust and in burial metamorphic sequences.

scholarly journals Spatial Relationships between Pockmarks and Sub-Seabed Gas in Fjordic Settings: Evidence from Loch Linnhe, West Scotland

Geosciences ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 283
Author(s):  
Allan Audsley ◽  
Tom Bradwell ◽  
John Howe ◽  
John Baxter
Keyword(s):  
Water Column ◽  
Seismic Reflection ◽  
Hot Spot ◽  
Geophysical Data ◽  
Spatial Relationships ◽  
Hydrocarbon Gases ◽  
Offshore Industry ◽  
Seismic Reflection Profiles ◽  
Spot Analysis ◽  
Sedimentary Carbon

Sub-seabed gas is commonly associated with seabed depressions known as pockmarks—the main venting sites for hydrocarbon gases to enter the water column. Sub-seabed gas accumulations are characterized by acoustically turbid or opaque zones in seismic reflection profiles, taking the form of gas blankets, curtains or plumes. How the migration of sub-seabed gas relates to the origin and distribution of pockmarks in nearshore and fjordic settings is not well understood. Using marine geophysical data from Loch Linnhe, a Scottish fjord, we show that shallow sub-seabed gas occurs predominantly within glaciomarine facies either as widespread blankets in basins or as isolated pockets. We use geospatial ‘hot-spot’ analysis conducted in ArcGIS to identify clusters of pockmarks and acoustic (sub-seabed) profile interpretation to identify the depth to gas front across the fjord. By combining these analyses, we find that the gas below most pockmarks in Loch Linnhe is between 1.4 m and 20 m deep. We anticipate that this work will help to understand the fate and mobility of sedimentary carbon in fjordic (marine) settings and advise offshore industry on the potential hazards posed by pockmarked seafloor regions even in nearshore settings.

Quantitative Determination of some Carbonate Minerals in Greenschist Facies Meta-volcanic Rocks

1972 ◽  
Vol 9 (1) ◽  
pp. 36-42 ◽  
Author(s):  
Calvert C. Bristol
Keyword(s):  
Standard Deviation ◽  
Quantitative Determination ◽  
Volcanic Rocks ◽  
Internal Standard ◽  
Greenschist Facies ◽  
Carbonate Mineral ◽  
Mineral Contents ◽  
X Ray ◽  
Fine Grained

X-ray powder diffraction methods, successful in quantitative determination of silicate minerals in fine-grained rocks, have been applied to the determination of calcite, dolomite, and magnesite in greenschist facies meta-volcanic rocks. Internal standard graphs employing two standards (NaCl and Mo) have been determined.Carbonate mineral modes (calcite and dolomite) for 6 greenschist facies meta-volcanic rocks obtained by the X-ray powder method have been compared to normative carbonate mineral contents calculated for the same rocks. This comparison showed a maximum variation of 7.7 wt.% between the X-ray modes and the normative carbonate mineral contents of the rocks. Maximum standard deviation for the X-ray modes of these rocks was equivalent to 4.4 wt.%.

scholarly journals Geomagnetic Survey to Explore High-Temperature Geothermal System in Blawan-Ijen, East Java, Indonesia

2018 ◽  
Vol 31 ◽  
pp. 02003 ◽  
Author(s):  
Yunus Daud ◽  
Syamsu Rosid ◽  
Fikri Fahmi ◽  
Faris Maulana Yunus ◽  
Reza Muflihendri
Keyword(s):  
High Temperature ◽  
Magnetic Anomaly ◽  
Volcanic Rocks ◽  
Hydrothermal Activity ◽  
Geothermal System ◽  
Geothermal Area ◽  
Variation Reduction ◽  
Geomagnetic Survey ◽  
Surface Alteration ◽  
Steep Topography

Ijen geothermal area is high-temperature geothermal system located in Bondowoso regency, East Java. It is categorized as caldera-hosted geothermal system which is covered by quaternary andesitic volcanic rocks with steep topography at the surrounding. Several surface thermal manifestations are found, such as altered rocks near Mt. Kukusan and a group of Blawan hotsprings in the northern part of the caldera. Geomagnetic survey was conducted at 72 stations which is distributed inside the caldera to delineate the existence of hydrothermal activity. Magnetic anomaly was obtained by reducing total magnetic measured on the field by IGRF and diurnal variation. Reduction to pole (RTP) method was applied with geomagnetic inclination of about -32°. In general, the result shows that high magnetic anomaly is distributed at the boundary of study area, while low magnetic anomaly is observed in the centre. The low anomaly indicates demagnetized rock that probably caused by hydrothermal activity. It has a good correlation with surface alteration observed close to Mt. Kukusan as well as high temperature reservoir drilled in the centre of caldera. Accordingly, the low magnetic anomaly also presents the possibility of geothermal reservoir in Ijen geothermal area.

scholarly journals Dominant Weathering Profile Assessment of Kebo-Butak Volcanic Rocks in Gedangsari and Ngawen area, Yogyakarta, Indonesia

2021 ◽  
Vol 6 (1) ◽  
Author(s):  
Fathan Hanifi Mada Mahendra ◽  
I Gde Budi Indrawan ◽  
Sugeng Sapto Surjono
Keyword(s):  
Volcanic Rocks ◽  
Sedimentary Rocks ◽  
Coarse Grained ◽  
Residual Soil ◽  
Geological Condition ◽  
Weathering Profile ◽  
Fine Grained ◽  
Degree Pattern ◽  
Weathering Degree ◽  
East West

The Gedangsari and Ngawen area is predominantly composed of volcanic and volcaniclastic sequencesdistributed east – west direction of the northern parts of Southern Mountain. The massive tectonism as well as tropical climatein this region have been producing weathering profiles in varying thickness which inevitably affects thegeotechnical properties. This study aims to assess the dominant weathering profileof the lower part of Kebo-Butak Formation as well as evaluating the distribution of the discontinuity. In order to know the dominant weathering profile and discontinuity evaluation, this study utilizes a total of  26 panels from five stations investigated through a geotechnical data acquisition including the geological condition, weathering zones, joint distribution, and discontinuity characteristics. The result shows four types of dominant weathering profiles in lower part of Kebo-Butak Formation called as dominant weathering profile A, B, C, and D. Profile A, B, C consisted of a relatively identical weathering degree pattern of fresh, slightly, moderately, completely weathered zone with the variation of thicknesses. However, the weathering degree in profile D reached the residual soil degree controlled by more intensive joints. The fine-grained sedimentary rocks also tends to have smaller spacing, shorter persistence, and higher weathering degree of discontinuities as compared to coarse-grained sedimentary rocks.

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