scholarly journals Till geochemical data for the south Core Zone, Quebec and Labrador (NTS 23-P and 23-I): till samples collected in 2014

2016 ◽  
Author(s):  
M B McClenaghan ◽  
R C Paulen ◽  
J M Rice ◽  
M Pyne ◽  
A Lion
Keyword(s):  
Geochemical Data ◽  
The South ◽  
Core Zone

Geologic-geochemical and modelling studies of hydrocarbon migration in the South Caspian basin

2020 ◽  
pp. 4-15
Author(s):  
M.F. Tagiyev ◽  
◽  
I.N. Askerov ◽  
◽  
◽  
...  
Keyword(s):  
Sedimentary Cover ◽  
Geochemical Data ◽  
Caspian Basin ◽  
Hydrocarbon Generation ◽  
The South ◽  
South Caspian Basin ◽  
Hydrocarbon Migration ◽  
Upward Migration ◽  
Modelling Studies ◽  
Hydrocarbon Charge

Based on pyrolysis data an overview is given on the generative potential and maturity of individual stratigraphic units in the South Caspian sedimentary cover. Furthermore, the pyrolysis analyses indicate that the Lower Pliocene Productive Series being immature itself is likely to have received hydrocarbon charge from the underlying older strata. The present state of the art in studying hydrocarbon migration and the "source-accumulation" type relationship between source sediments and reservoired oils in the South Caspian basin are touched upon. The views of and geochemical arguments by different authors for charging the Lower Pliocene Productive Series reservoirs with hydrocarbons from the underlying Oligocene-Miocene source layers are presented. Quantitative aspects of hydrocarbon generation, fluid dynamics, and formation of anomalous temperature & pressure fields based on the results of basin modelling in Azerbaijan are considered. Based on geochemical data analysis and modelling studies, as well as honouring reports by other workers the importance and necessity of upward migration for hydrocarbon transfer from deep generation centers to reservoirs of the Productive Series are shown.

Occurrence and significance of Silurian K-bentonite beds at Arisaig, Nova Scotia, eastern Canada

1997 ◽  
Vol 34 (12) ◽  
pp. 1630-1643 ◽  
Author(s):  
Stig M. Bergström ◽  
Warren D. Huff ◽  
Dennis R. Kolata ◽  
Michael J. Melchin
Keyword(s):  
Nova Scotia ◽  
North America ◽  
Geochemical Data ◽  
Northern Coast ◽  
Calc Alkaline ◽  
The South ◽  
Eastern Canada ◽  
Critical Information ◽  
Plate Margin ◽  
Alkaline Magmas

The most extensive succession of K-bentonite beds known in the Silurian of North America occurs at Arisaig on the northern coast of Nova Scotia. At least 40 ash beds are present in the Llandoverian Ross Brook Formation and at least four in the early Ludlovian McAdam Brook Formation. Most of the beds are thin (< 5 cm), but one bed (the Smith Brook K-bentonite bed) in the late Llandoverian crenulata Zone and another (the McAdam Brook K-bentonite bed) in the early Ludlovian nilssoni Zone each reach a thickness of 20 cm. New graptolite collections provide critical information on the biostratigraphic position of the K-bentonite beds in the Ross Brook Formation. Geochemical data show that the Arisaig ash beds represent calc-alkaline magmas from plate margin, subduction-related volcanic vents. Differences in K-bentonite stratigraphic distribution, combined with paleogeographic considerations, suggest that the volcanoes were located much farther to the south in the Iapetus than the source volcanoes of the British–Baltoscandian Llandoverian K-bentonites.

La Primavera caldera (Mexico): Structure inferred from gravity and hydrogeological considerations

Geophysics ◽  
1991 ◽  
Vol 56 (7) ◽  
pp. 992-1002 ◽  
Author(s):  
M. A. Alatorre‐Zamora ◽  
J. O. Campos‐Enríquez
Keyword(s):  
Structural Model ◽  
Structural Information ◽  
Gravity Data ◽  
Middle Part ◽  
Geochemical Data ◽  
Gravity Modeling ◽  
The South ◽  
Geothermal Fluids ◽  
Production Zone ◽  
Structural High

La Primavera geothermal field (Mexico) is associated with a Pleistocene rhyolitic caldera. This gravity study was conducted to assist its development and explotation. Digital processing of the gravity data (upward and downward continuations, vertical derivatives) enabled delineation of the main features of the caldera’s subsurficial structure. A 3-D structural model was established, which could be supported by gravity modeling (2-D and 3-D forward modeling). Accordingly, the caldera is featured by an asymmetric subsurface structure: a major depression in its northern half, and a boomerang‐shaped structural high to the south. Lineaments reflecting the regional northwest‐southeast and northeast‐southwest structural fabric were observed. The basal volcanics units are affected by lineaments of the northwest‐southeast system, whereas the northeast‐southwest system affects only the shallower units. The structural high has a northwest‐southeast trend at the western and southwestern portion of the caldera. From its middle part eastward, it has a northeast‐southwest direction. The actual geothermal production zone is located above this structural high, on the portion where it changes orientation. Correlation with hydrogeological and geochemical data enabled interpreting the different geologic structures in the context of the hydrothermal system: at depth the northwest‐southeast structures seem to control lateral fluid migration, and connect areas of enhanced permeability (i.e., the central production zone and the hydrothermal manifestations located at the caldera’s western rim). Enhanced zones of fracturing favorable for entrapping hydrothermal fluids and structural accidents that may act as conduits (respectively as barriers) for fluids are delineated. In particular, a new target zone, where the production of geothermal fluids may extend, has been identified to the south of the production zone. The structural image elaborated here constitutes a geologic frame for the prevailing hydrogeological conceptual model. This structural information is also useful for the tasks of selecting sites for the reinjection of geothermal brines.

scholarly journals Origin of last-glacial loess in the western Yukon-Tanana Upland, central Alaska, USA

2018 ◽  
Vol 89 (3) ◽  
pp. 797-819 ◽  
Author(s):  
Daniel R. Muhs ◽  
Jeffrey S. Pigati ◽  
James R. Budahn ◽  
Gary L. Skipp ◽  
E. Arthur Bettis ◽  
...  
Keyword(s):  
Drainage Basin ◽  
Coarse Grained ◽  
Geochemical Data ◽  
Glacial Period ◽  
The South ◽  
Last Glacial Period ◽  
Last Glacial ◽  
Recent Climate ◽  
Loess Deposits ◽  
The Last Glacial

AbstractLoess is widespread over Alaska, and its accumulation has traditionally been associated with glacial periods. Surprisingly, loess deposits securely dated to the last glacial period are rare in Alaska, and paleowind reconstructions for this time period are limited to inferences from dune orientations. We report a rare occurrence of loess deposits dating to the last glacial period, ~19 ka to ~12 ka, in the Yukon-Tanana Upland. Loess in this area is very coarse grained (abundant coarse silt), with decreases in particle size moving south of the Yukon River, implying that the drainage basin of this river was the main source. Geochemical data show, however, that the Tanana River valley to the south is also a likely distal source. The occurrence of last-glacial loess with sources to both the south and north is explained by both regional, synoptic-scale winds from the northeast and opposing katabatic winds that could have developed from expanded glaciers in both the Brooks Range to the north and the Alaska Range to the south. Based on a comparison with recent climate modeling for the last glacial period, seasonality of dust transport may also have played a role in bringing about contributions from both northern and southern sources.

scholarly journals Structural Controls on Shallow Cenozoic Fluid Flow in the Otago Schist, New Zealand

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-25
Author(s):  
Simon C. Holbek ◽  
Madison Frank ◽  
James M. Scott ◽  
Steven A. F. Smith ◽  
Petrus J. le Roux ◽  
...  
Keyword(s):  
Fluid Flow ◽  
New Zealand ◽  
Hydrothermal Systems ◽  
Strike Slip ◽  
Geochemical Data ◽  
Small Displacement ◽  
Type I ◽  
The South ◽  
Vein Formation ◽  
Otago Schist

The Otago Schist in the South Island of New Zealand represents an exhumed Mesozoic accretionary prism. Two coastal areas (Akatore Creek and Bruce Rocks) south of Dunedin preserve structural and geochemical evidence for the development of postmetamorphic hydrothermal systems that involved widespread fluid-rock reaction at shallow crustal depths. The Jurassic to Triassic pumpellyite-actinolite (Akatore Creek) to upper greenschist facies (Bruce Rocks) metamorphic fabrics were crosscut by sets of regionally extensive Cretaceous exhumation joints. Many of the joints were subsequently reactivated to form networks of small-displacement (<metres) strike-slip faults containing cemented fault breccias and veins composed of hydrothermal calcite, siderite, and ankerite. Paleostress analysis performed on infrequent fault slickenlines indicates an overall strike-slip paleostress regime and a paleo-σ1 orientation (azimuth 094°) similar to the contemporary σ1 orientation in Otago and Canterbury (azimuth c. 110°-120°). High δ18O values in vein calcite (δ18OVPDB=21 to 28‰), together with the predominance of Type I calcite twins, suggest that vein formation occurred at low temperatures (<200°C) in the shallow crust and was associated with strongly channelized fluid flow along the joint and fault networks. Mass-balance calculations performed on samples from carbonate alteration zones show that significant mobilisation of elements occurred during fluid flow and fluid-rock reaction. Whole-rock and in situ carbonate 87Sr/86Sr data indicate varying degrees of interaction between the hydrothermal fluids and the host rock schists. Fluids were likely derived from the breakdown of metamorphic Ca-rich mineral phases with low 87Rb in the host schists (e.g., epidote or calcite), as well as more radiogenic components such as mica. Overall, the field and geochemical data suggest that shallow fluid flow in the field areas was channelized along foliation surfaces, exhumation joints, and networks of brittle faults, and that these structures controlled the distribution of fluid-rock reactions and hydrothermal veins. The brittle fault networks and associated hydrothermal systems are interpreted to have formed after the onset of Early Miocene compression in the South Island and may represent the manifestation of fracturing and fluid flow associated with reverse reactivation of regional-scale faults such as the nearby Akatore Fault.

Clay mineral sources of the Grenada Basin, Southeastern Caribbean

Clay Minerals ◽  
1987 ◽  
Vol 22 (4) ◽  
pp. 395-400 ◽  
Author(s):  
V. Gandais
Keyword(s):  
Clay Mineral ◽  
Lesser Antilles ◽  
Geochemical Data ◽  
South American ◽  
American Continent ◽  
The South ◽  
Mineralogical Analysis ◽  
South American Continent ◽  
Lesser Antilles Arc ◽  
American Contribution

AbstractThis study of the Quaternary clay sedimentation in the Grenada Basin (Southeastern Caribbean) is based on six cores raised from depths of 1800 to 3000 m. Mineralogical analysis of <2 µm and <0·3 µm fractions revealed the presence of a four-component association — smectites, illite, kaolinite and chlorite — in which smectites were always dominant. These minerals were derived from two sources: the Lesser Antilles Arc, which contributed only smectites and kaolinite, and the South American continent, where smectites, kaolinite, chlorite and illite coexist. Geochemical data indicate that Ba and Cr are specific indicators of the South American minerals, whereas Cu characterizes the Antillean clays. The South American contribution, now prevailing, was less important during the Sangamon. The Antillean contribution was episodically predominant during the Wisconsin.

Occurrence and probable source of chromium enrichment in Permian coals, South Africa

2021 ◽  
Author(s):  
N.J. Wagner ◽  
M.L. Mokwena ◽  
A. Kolker
Keyword(s):  
South Africa ◽  
South African ◽  
Bushveld Complex ◽  
Correlation Coefficients ◽  
Geochemical Data ◽  
Selective Leaching ◽  
The South ◽  
Modes Of Occurrence ◽  
Coal Characterization ◽  
Chromium Enrichment

Abstract The trace element data pool for South African coals is limited. However, certain elements are reported as occurring in considerably higher concentrations than global average values. These elements include chromium (Cr), as well as manganese (Mn), cobalt (Co), and molybdenum (Mo), with Cr showing the most consistent enrichment. The aim of this study was to investigate the occurrence of Cr in South African coals sampled from five coalfields, and to assess the possible source of Cr. A total of 21 run-of-mine (ROM) coal samples from the Waterberg, Soutpansberg, Witbank, Highveld, and the Nongoma Coalfields were obtained from active mines. Coal characterization, mineralogy, and geochemical data were compiled. The Cr values for the Waterberg (23 to 28 ppm), Soutpansberg (4.7 to 43 ppm), Witbank (24 to 37 ppm), and Highveld (33 to 37 ppm) coal samples are higher than those for the Nongoma coals (1.2 to 2.5 ppm), and, in nearly every case, higher than the Clarke value for hard coals (17 ppm). Correlation coefficients, density fractionation, and selective leaching were used to infer (indirect) modes of occurrence. A dominant silicate (clay) affinity was determined with Cr, as well as an organic affinity in the ROM samples. The Nongoma coals, with illite and no kaolinite, have extremely low Cr values. The other samples are enriched in kaolinite and also have a high Cr content. Chromium values as high as 67 ppm were reported for 1.4 RD float fraction samples, indicating a positive correlation with organic matter. A Cr - silicate association was observed following selective leaching. These results imply multiple modes of occurrence of Cr in the South African samples, in agreement with studies conducted globally. Chromium in the South African coals could have originated from the Bushveld Complex (approximately two billion years old), the largest Cr reserve in South Africa, which predates coal formation (approximately 299 to 252 million years ago) and is proximal to the coalfields. The Cr, seemingly not associated with chromite, may have been redistributed in the peat swamps during peat deposition, accumulating in the sediments and organic material. The Nongoma Coalfield is the farthest distance from the possible Bushveld Complex Cr source, and these samples are depleted in Cr.

scholarly journals Chronostratigraphy of the Hottah terrane and Great Bear magmatic zone of Wopmay Orogen, Canada, and exploration of a terrane translation model

2015 ◽  
Vol 52 (12) ◽  
pp. 1062-1092 ◽  
Author(s):  
Luke Ootes ◽  
William J. Davis ◽  
Valerie A. Jackson ◽  
Otto van Breemen
Keyword(s):  
Subduction Zones ◽  
Shear Zones ◽  
Geochemical Data ◽  
The South ◽  
Active Margin ◽  
Slave Craton ◽  
Tectonic History ◽  
Zircon Crystallization ◽  
And Migration ◽  
Subduction System

The Paleoproterozoic Hottah terrane is the westernmost exposed bedrock of the Canadian Shield and a critical component for understanding the evolution of the Wopmay Orogen. Thirteen new high-precision U–Pb zircon crystallization ages are presented and support field observations of a volcano-plutonic continuum from Hottah terrane through to the end of the Great Bear magmatism, from >1950 to 1850 Ma. The new crystallization ages, new geochemical data, and newly published detrital zircon U–Pb data are used to challenge hitherto accepted models for the evolution of the Hottah terrane as an exotic arc and microcontinent that arrived over a west-dipping subduction zone and collided with the Slave craton at ca. 1.88 Ga. Although the Hottah terrane does have a tectonic history that is distinct from that of the neighbouring Slave craton, it shares a temporal history with a number of domains to the south and east — domains that were tied to the Slave craton by ca. 1.97 Ga. It is interpreted herein that Hottah terrane began to the south of its current position and evolved in an active margin over an always east-dipping subduction system that began prior to ca. 2.0 Ga and continued to ca. 1.85 Ga, and underwent tectonic switching and migration. The stratigraphy of the ca. 1913–1900 Ma Hottah plutonic complex and Bell Island Bay Group includes a subaerial rifting arc sequence, followed by basinal opening represented by marginal marine quartz arenite and overlying ca. 1893 Ma pillowed basalt flows and lesser rhyodacites. We interpret this stratigraphy to record Hottah terrane rifting off its parental arc crust — in essence the birth of the new Hottah terrane. This model is similar to rapidly rifting arcs in active margins — for example, modern Baja California. These rifts generally occur at the transition between subduction zones (e.g., Cocos–Rivera plates) and transtensional shear zones (e.g., San Andreas fault), and we suggest that extension-driven transtensional shearing, or, more simply, terrane translation, was responsible for the evolution of Bell Island Bay Group stratigraphy and that it transported this newly born Hottah terrane laterally (northward in modern coordinates), arriving adjacent to the Slave craton at ca. 1.88 Ga. Renewed east-dipping subduction led to the Great Bear arc flare-up at ca. 1876 Ma, continuing to ca. 1869 Ma. This was followed by voluminous Great Bear plutonism until ca. 1855 Ma. The model implies that it was the westerly Nahanni terrane and its subducting oceanic crust that collided with this active margin, shutting down the >120 million year old, east-dipping subduction system.

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