scholarly journals Lithostratigraphy, geology and geochemistry of the volcanic rocks of the Vaigat Formation on Disko and Nuussuaq, Paleocene of West Greenland

2017 ◽  
Vol 39 ◽  
pp. 1-244
Author(s):  
Asger Ken Pedersen ◽  
Lotte Melchior Larsen ◽  
Gunver Krarup Pedersen
Keyword(s):  
Volcanic Rocks ◽  
First Episode ◽  
The Third ◽  
The North ◽  
Rock Types ◽  
Magma Reservoirs ◽  
Native Iron ◽  
Volcanic Succession ◽  
High Level ◽  
Contamination Events

The Paleocene volcanic rocks in the Nuussuaq Basin on Disko and Nuussuaq comprise the Vaigat Formation (c. 62–61 Ma) and the Maligât Formation (c. 60 Ma). The Vaigat Formation in this area is 0–1600 m thick and is dominated by olivine-rich picrites. The formation was deposited during three volcanic episodes and is divided into 10 formally defined members and about 20 informal units. The first episode gave rise to the Anaanaa Member. The second episode gave rise to the Naujánguit Member, which is intercalated with the minor, crustally contaminated Nuusap Qaqqarsua, Nuuk Killeq, Asuk, Tunoqqu and Kûgánguaq members and the uncontaminated Qordlortorssuaq Member. The third episode gave rise to the Ordlingassoq Member and the minor alkaline Manîtdlat Member. Contemporaneous sediments deposited during the first two episodes are the marine Eqalulik Formation, and during the third episode the nonmarine Atanikerluk Formation. During the second episode, the polarity of the geomagnetic field changed from normal (Chron C27n) via a transition zone to reversed (C26r). The deposits of the first volcanic episode are situated on western Nuussuaq. During the second and third episodes, the volcanism gradually spread eastwards and southwards so that the Vaigat Formation now forms a domed structure, thickest in the north, thinning out on northern Disko and reaching eastwards to the high gneiss country on central Nuussuaq. The earliest eruptions took place on the sea floor and quickly built up a subaerial lava plateau. All three episodes gave rise to complicated facies changes between subaqueous and subaerial eruption products caused by the eastmoving volcanism, subsidence, volcanic aggradation and blockage of the sea connection against the elevated eastern gneiss country. Eruption sites are widespread for all three volcanic episodes. Within certain time periods, a number of contemporaneous high-level magma reservoirs developed within sediments of the Nuussuaq Group, and the crustally contaminated members formed in these reservoirs by reaction between Mg-rich magmas and sediments. The uncontaminated rocks in the Vaigat Formation are picrites with 12–31 wt% MgO and subordinate basalts with 7–12 wt% MgO. The crustally contaminated rocks range from silicic picrites with 12–16 wt% MgO (Nuusap Qaqqarsua Member) to native-iron-bearing magnesian andesites with 6–10 wt% MgO and up to 62 wt% SiO2 (Asuk Member). The Asuk Member includes unique, strongly reduced rock types with native iron, graphite and sulfide. The contaminated units have individually distinct compositions, indicating individually different contamination events. The alkaline Manîtdlat Member contains an enriched lithospheric component. Present-day seeps of migrated oil are widespread in the oldest part of the volcanic succession on western Nuussuaq. Some of the contaminated magmas in the Asuk and Kûgánguaq members have fractionated sulfides with Cu and Ni and have been explored for nickel and platinum-group elements. 

The Sabaloka igenous complex, Sudan

1977 ◽  
Vol 287 (1348) ◽  
pp. 595-633 ◽  
Keyword(s):  
Volcanic Rocks ◽  
Large Mass ◽  
Fracture System ◽  
Magma Chambers ◽  
Quartz Syenite ◽  
Western Africa ◽  
The North ◽  
Rock Types ◽  
Early Palaeozoic ◽  
Volcanic Succession

Sabaloka is one of the best exposed and most accessible of a large number of Younger Granite complexes in Sudan. These complexes have close affinities with the Younger Granites of western Africa and like them range widely in age. Sabaloka itself probably dates from the Proterozoic or early Palaeozoic. The paper includes a detailed map and description of the complex and presents the results of 20 new whole-rock chemical analyses. Of the two main centres at Sabaloka, the large Cauldron Complex comprises a subsided block of basement overlain by up to 2 km of volcanic rocks and circumscribed by a polygonal zone of ring-fracturing. The fracture system was intruded by a ringdyke of porphyritic microgranite after eruption of the volcanic rocks, and at about the same time a boss of mica granite with associated tin-tungsten mineralization was injected into the subsided block. There is also gravimetric evidence of subsurface granite intrusions in both the north and south of the cauldron, but no indications of any large mass of basic rock. Nearly all of the volcanic and intrusive rocks of the Cauldron Complex are thoroughly acidic, but a thin group of basaltic lavas lies at the base of the volcanic succession and a few minor intrusions are of basic and intermediate composition. The acidic rocks include metaluminous and subaluminous types, but peralkaline rocks are either absent or very minor in amount and altered beyond recognition. Lavas dominate the lower part of the volcanic succession whereas rhyolitic ignimbrites compose most of the upper part. Of the two main episodes of subsidence which formed the cauldron the first followed upon eruption of the lavas and produced a structural basin centred on the eastern margin of the present complex. Subsequent establishment of the ring-fracture system appears to have been consequent upon an extension of the magma chambers to the north, and was accompanied by voluminous ash-flow eruptions and the formation of a caldera. The second major subsidence post-dated all the volcanic rocks still preserved, and was probably followed by resurgent doming in the north, though the evidence on this point is not conclusive. The Cauldron Complex is classified as a ‘Valles type’ of caldera volcano. The much smaller Tuleih Complex lies north of the Cauldron and includes a boss of quartz-syenite and subacid granite together with a plexus of smaller intrusions which include peralkaline intermediate and acidic rocks of comenditic character. The age of these intrusions relative to the Cauldron Complex is not known. The chemistry of these various rock types reflects in many respects their close similarity to the Younger Granite association of western Africa, although the rocks of the Cauldron Complex are somewhat poorer in soda than most analysed acidic rocks from the Nigerian Younger Granites.

scholarly journals Lithostratigraphy, geology and geochemistry of the volcanic rocks of the Maligât Formation and associated intrusions on Disko and Nuussuaq, Paleocene of West Greenland

2018 ◽  
Vol 40 ◽  
pp. 1-239 ◽  
Author(s):  
Asger Ken Pedersen ◽  
Lotte Melchior Larsen ◽  
Gunver Krarup Pedersen
Keyword(s):  
Basaltic Andesite ◽  
Volcanic Rocks ◽  
Middle Part ◽  
Lava Flows ◽  
Lake Basin ◽  
The North ◽  
Rock Types ◽  
Native Iron ◽  
North Eastern ◽  
Iron Bearing

The Paleocene volcanic rocks in the Nuussuaq Basin on Disko and Nuussuaq comprise the picritic Vaigat Formation (c. 62–61 Ma) and the overlying basaltic Maligât Formation (c. 60 Ma). The Maligât Formation is up to 2000 m thick on western Disko where the top of the formation is least eroded. The formation is divided into four members, the Rinks Dal, Nordfjord, Niaqussat and Sapernuvik members, which are formally defined here. On central and eastern Disko and Nuussuaq the Maligât Formation lavas are interbedded with fluvial and lacustrine sandstones and mudstones of the Atanikerluk Formation.The Rinks Dal Member is the lowest member and originally constituted around 61% by volume of the formation. It is divided into 12 informal units based on chemically recognisable oscillations in the fractionation state of the basalts. The oldest units are present on central and south Disko close to the Disko Gneiss Ridge. The younger lavas spread farther to the east, north and west, filled the Assoq Lake basin east of the ridge and gradually onlapped the shield of the earlier Vaigat Formation that rose to the north. Only the lavas of the upper Rinks Dal Member reached far into Nuussuaq. The lavas are generally not crustally contaminated and comprise evolved basalts with 4.4–9.2 wt% MgO and a few picrites. The most evolved basalts with 3.2–4.8 wt% TiO2 occur in the middle part of the member where they form the Akuarut unit. The Nordfjord Member originally constituted around 6% by volume of the formation. It is not subdivided because the lithological variability is local. The member is widespread but has its depocentre on north-western Disko where thicknesses reach 350 m and eruption sites, intermediate lavas and acid tuffs are present. Over most of the area the member consists of just a few lava flows with combined thicknesses of 30–100 m. The member has a very diverse lithology with rock types ranging from silicic basalt with 5.3–10.0 wt% MgO through magnesian basaltic andesite and andesite with 2.4–10.6 wt% MgO to dacite with 1.2–2.2 wt% MgO. Rhyolite with 0.2–1.2 wt% MgO and up to 77 wt% SiO2 occur in tuffs and conglomerate clasts. All rocks are crustally contaminated and some are native-iron-bearing. The Niaqussat Member originally constituted around 33% by volume of the formation. It is subdivided into three informal units. The member is widespread, but much of it has been removed by erosion. Lithologies in the lower unit range from silicic picrite with up to 15 wt% MgO to basalt with 6–12 wt% MgO and a few basaltic andesite flows. The middle and upper parts of the Niaqussat Member comprise more evolved basalts with respectively 6.1–7.2 wt% MgO and 4.9–6.4 wt% MgO. All rocks are crustally contaminated and a few lava flows are native-iron-bearing. The Sapernuvik Member comprises three uncontaminated basalt flows with 7.5–10.7 wt% MgO. It is only preserved in a small area on western Disko. Dyke systems with up to 80 km long dykes and subvolcanic intrusions associated with the Nordfjord and Niaqussat members occur on western and north-eastern Disko. The rocks are crustally contaminated and range from silicic basalt with 4–13 wt% MgO to magnesian andesite with 3–10 wt% MgO. They commonly form composite intrusions, some of which contain accumulations of native iron and sulfides. The contaminants are carbon- and sulfur-bearing sediments of the Nuussuaq Group. Major contamination mechanisms were mixing with partial melts from the sediment sidewall and xenoliths and selective exchange of some elements, including carbon and sulfur, between magma and sediment. Degrees of contamination vary from 2−5% in the basalts to 10−50% in the more silicic rocks. No rocks more evolved than basalt were produced by ordinary fractional crystallisation.

scholarly journals Filling and plugging of a marine basin by volcanic rocks: the Tunoqqu Member of the Lower Tertiary Vaigat Formation on Nuussuaq, central West Greenland

1996 ◽  
Vol 171 ◽  
pp. 5-28
Author(s):  
A.K Pedersen ◽  
L.M Larsen ◽  
G.K Pedersen ◽  
K.S Dueholm
Keyword(s):  
Volcanic Rocks ◽  
Water Levels ◽  
North Coast ◽  
Magma Chambers ◽  
Tectonic Control ◽  
Crustal Rocks ◽  
The North ◽  
High Level ◽  
Marine Embayment ◽  
Volcanic Cycles

The volcanic Tunoqqu Member formed at the end of the second of three volcanic cycles in the Paleocene Vaigat Formation. The Tunoqqu Member consists of brown aphyric and feldspar-phyric basalts and forms a marker horizon within the grey picritic rocks of the Vaigat Formation. Most of the basalts are siliceous and were produced by contamination with crustal rocks of magmas ranging in composition from picrite to evolved basalt. Some of the basalts were erupted from local volcanic centres of which four have been identified, whereas other basalts form more regional flows. The four identified eruption centres are located along fault lines and zones of uplift and subsidence, indicating tectonic control. Tectonic control is also inferred to be important in terminating the volcanic cycle and causing the development of high-level magma chambers where the magmas stagnated, fractionated, and became contaminated. The basalts of the Tunoqqu Member form subaerial lava flows in western Nuussuaq. Central Nuussuaq constituted a marine embayment in which the volcanics were deposited as eastward prograding foreset-bedded hyaloclastite breccia fans which indicate water depths of up to 160 m. Eastern Nuussuaq was a gneiss highland with a more than 700 m high NW-SE-elongated gneiss promontory stretching into the sea. During Tunoqqu Member time the volcanic rocks reached the gneiss promontory and blocked the outlet from the south to the sea in the north. This resulted in increased water levels in the enclosed embayment and transformation of the outlet into a torrential river. This river eroded the concomitantly forming Tunoqqu Member volcanics and the gneiss promontory and deposited the material in up to more than 250 m thick foreset-bedded boulder conglomerates in the sea where the north coast of Nuussuaq is now situated.

A re-examination of the type area of the Devono-Mississippian Cariboo Orogeny, central British Columbia

1981 ◽  
Vol 18 (12) ◽  
pp. 1767-1775 ◽  
Author(s):  
L. C. Struik
Keyword(s):  
British Columbia ◽  
North American ◽  
Volcanic Rocks ◽  
The Other ◽  
Type Locality ◽  
The Third ◽  
The North ◽  
Early Mesozoic ◽  
Type Area ◽  
North American Craton

Three tectonostratigraphic successions are established from remapping of the area near Barkerville and Cariboo River. The first, of Late Proterozoic to Cambrian sediments, was deposited on the shallow to moderately deep platformal shelf west of and derived from the exposed North American craton. The second is an unconformably overlying Ordovician to Permian sequence of sedimentary and volcanic rocks representing a basinal environment with periodic highs. These packages of sediments were deposited on the North American craton and its western transitional extensions. The third succession, composed of oceanic chert and basalt of the Permo-Pennsylvanian Antler Formation, was thrust eastward over the other two during the early Mesozoic. The three successions were folded, faulted, and metamorphosed during the mid-Mesozoic Columbian Orogeny. The Devono-Mississippian Cariboo Orogeny, which was thought to have affected all of the first sequence and part of the second, could not be documented in its type locality. The geology of the Barkerville – Cariboo River area has many similarities with that of Selwyn Basin and Cassiar platform of northern British Columbia and Yukon.

scholarly journals Understanding the offshore flood basalt sequence using onshore volcanic facies analogues: an example from the Faroe–Shetland basin

2009 ◽  
Vol 146 (3) ◽  
pp. 353-367 ◽  
Author(s):  
DOUGAL A. JERRAM ◽  
RICHARD T. SINGLE ◽  
RICHARD W. HOBBS ◽  
CATHERINE E. NELSON
Keyword(s):  
Volcanic Rocks ◽  
Flood Basalt ◽  
Reflection Seismology ◽  
Flood Basalts ◽  
Geological Interpretation ◽  
Seismic Modelling ◽  
The North ◽  
Volcanic Facies ◽  
Volcanic Succession ◽  
Simple Flows

AbstractFlood basalts in associated volcanic rifted margins, such as the North Atlantic Igneous Province, have a significant component of lavas which are preserved in the present day in an offshore setting. A close inspection of the internal facies architecture of flood basalts onshore provides a framework to interpret the offshore sequences imaged by remote techniques such as reflection seismology. A geological interpretation of the offshore lava sequences in the Faroe–Shetland Basin, using constraints from onshore analogues such as the Faroe Islands, allows for the identification of a series of lava sequences which have characteristic properties so that they can be grouped. These are tabular simple flows, compound-braided flows, and sub-aqueously deposited hyaloclastite facies. The succession of volcanic rocks calculated in this study has a maximum thickness in excess of 6800 m. Down to the top of the sub-volcanic sediments, the offshore volcanic succession has a thickness of about 2700 m where it can be clearly identified across much of the area, with a further 2700 m or more of volcanic rock estimated from the combined gravity and seismic modelling to the north and west of the region. A large palaeo-waterbody is identified on the basis of a hyaloclastite front/apron consisting of a series of clinoforms prograding towards the eastern part of the basin. This body was > 500 m deep, must have been present at the onset of volcanism into this region, and parts of the water body would have been present during the continued stages of volcanism as indicated by the distribution of the hyaloclastite apron.

scholarly journals EARTHQUAKE HAZARD ANALYSIS OF NGANJUK REGENCY

2020 ◽  
Vol 15 (1) ◽  
pp. 52-62
Author(s):  
Wisyanto Wisyanto ◽  
Heru Sri Naryanto
Keyword(s):  
Hazard Analysis ◽  
Earthquake Hazard ◽  
Middle Level ◽  
Probabilistic Methods ◽  
The North ◽  
Rock Types ◽  
Southwest Region ◽  
Earthquake Hazard Analysis ◽  
The Difference ◽  
High Level

Earthquake hazard must be considered by many regions in Indonesia. This is including Nganjuk Regency, the area with intensifies development and where the longest dam in Indonesia is being built. Earthquake hazard studies are conducted using two methods, namely semi-deterministic and probabilistic methods. The results of analyses using the first method show that Nganjuk Regency can be divided into 3 classes of hazards, low level in the southwest region, middle level in the north and high level in the middle of the region. Analyses using the second method reveal that Nganjuk Regency can be classified into two categories, the southwest region which has the potential to experience very strong shocks with an intensity of upper VII MMI to lower VIII MMI and the northern and central region which has the potential of destructive shocks with an intensity of middle VIII MMI. The difference in the results from the two methods can be eliminated by classifying the detail of the existing soil/rock types.

scholarly journals Palynostratigraphy of the Lower Tertiary volcanics and marine clastic sediments in the southern part of the West Greenland Basin: implications for the timing and duration of the volcanism

1992 ◽  
Vol 154 ◽  
pp. 13-31
Author(s):  
S Piasecki ◽  
L.M Larsen ◽  
A.K Pedersen ◽  
G.K Pedersen
Keyword(s):  
Volcanic Activity ◽  
Volcanic Rocks ◽  
Dinoflagellate Cysts ◽  
East Greenland ◽  
West Greenland ◽  
Second Stage ◽  
The Third ◽  
The North ◽  
Clastic Sediments ◽  
Third Stage

Volcanic rocks, forming hyaloclastites and subaqueous lava flows, were deposited intercalated with clastic sediments in a water-filled basin in West Greenland in the Early Tertiary. Three main stages of basin infilling occurred in the Disko-Nuussuaq area. The distribution of dinoflagellate cysts in the sediments shows that the basin was marine in the first stage and non-marine in the second stage of infilling. In the third stage the basin was displaced towards the south and was marginally marine. The dinoflagellate cysts form a typical mid-Paleocene assemblage which may be correlated with the calcareous nannoplankton (NP) zonation. The stratigraphically lowest investigated localities are coeval with the uppermost part of nannoplankton zone NP4, whereas the overlying localities within the marine basin (first stage) may be correlated with NP5-6. The localities from the non-marine second stage cannot be correlated with the NP zonation because they do not contain dinoflagellate cysts. Localities from the third stage are coeval with NP7-8. Younger volcanics are subaerially deposited. The total known range of the volcanics now falls within the NP3 to NP8 interval, giving a minimum duration for the main plateau-building stage of the volcanism of 4–6 million years. The subaerial basalts have previously been found to be mainly reversely magnetised, with one normally magnetised sequence which can now be stratigraphically correlated with NP4, and thereby identified as anomaly 27. The basalts in East Greenland started erupting during the NP9 zone, so that the volcanic activity in East Greenland largely succeeded that in West Greenland. In relation to the postulated mantle plume in the North Atlantic this means that the volcanic activity started in the peripheral part of the plume and only later switched to the central part.

Exploration challenges along the North Atlantic volcanic margins: the intra-volcanic sandstone play in subsurface and outcrop

2016 ◽  
Vol 8 (1) ◽  
pp. 231-245 ◽  
Author(s):  
Michael Larsen ◽  
Brian Bell ◽  
Pierpaolo Guarnieri ◽  
Henrik Vosgerau ◽  
Rikke Weibel
Keyword(s):  
North Atlantic ◽  
Relative Concentration ◽  
Volcanic Rocks ◽  
Mineralogical Composition ◽  
Petroleum Exploration ◽  
Reservoir Properties ◽  
Continental Flood Basalts ◽  
The North ◽  
The North Atlantic ◽  
Volcanic Succession

AbstractThe margins of the North Atlantic rift are covered by an extensive succession of volcanic rocks, with up to 5 km of continental flood basalts, hyaloclastites and interbedded sedimentary rocks. The volcanic succession deteriorates seismic imaging and has hampered petroleum exploration in these areas. Focused research and pioneering exploration activity, however, has improved the understanding and development of new play models in volcanic-influenced basins. In 2004, the Rosebank discovery finally proved that intra-volcanic siliciclastic sandstones of the Flett Formation may form attractive hydrocarbon reservoirs in the Faroe–Shetland Basin.The Kangerlussuaq Basin in southern East Greenland offers a unique opportunity to study the interaction of siliciclastic sediments with lavas and various volcaniclastic units. It is demonstrated that: (1) laterally extensive siliciclastic sedimentary units are present in the lower part of the volcanic succession; (2) the morphology of the lavas controlled variations in sandstone geometry and thickness; and (3) deposition of the interbedded sediments and lavas occurred in a low-relief environment close to sea level. The mineralogical composition of the intra-volcanic sediments is highly variable, ranging from siliciclastic to purely volcaniclastic. Diagenetic studies suggest that the nature of the volcanic component in volcaniclastic sandstones is more important to reservoir properties than the relative concentration.

scholarly journals SYCLE ONE SCHOOL PRINCIPLES’TEACHER JOB SATISFACTION IN NORTH AL BATINAH IN THE SULTANATE OF OMAN

2022 ◽  
Vol 04 (01) ◽  
pp. 503-527
Author(s):  
Mohammed Saleh ALAJMI ◽  
Naima Salim Said AL RISI
Keyword(s):  
Job Satisfaction ◽  
Leadership Style ◽  
Correlation Method ◽  
School Principal ◽  
First Episode ◽  
Democratic Leadership ◽  
Female Principals ◽  
The North ◽  
High Level ◽  
Leadership Pattern

The study aimed to identify the leadership patterns practiced by the female principals of the first circle schools as seen by the teachers of the first field in the province of North Al Batina, and to identify the level of job satisfaction of the teachers of the first field, and to reveal the correlation between the leadership patterns of the female principals of the first circle and the job satisfaction of the teachers of the first field. The researcher used the descriptive correlation method, and designed two questionnaires: the questionnaire measuring the leadership patterns of the female school principals of the first episode in North Al-Batina, and the other the questionnaire of the measurement of job satisfaction in the teachers of the first field in The North Al-Batina, each questionnaire contained 30 paragraphs, and included three axes. The results of the study showed that the democratic leadership style came first, with a mathematical average of 4.45,which is the most practiced pattern among the principals of the first circle schools in the province of North Al-Batina, followed by the autocratic leadership pattern, the leadership pattern, asindicated by the results of the study to the high level of job satisfaction in all axes with a mathematical average of 4.52, and came first the center of job satisfaction related to satisfaction with the nature of work, with a mathematical average of 4.62, followed by the axis of satisfaction of school mates, and came in third place the focus of satisfaction for the school principal, and also indicated the results of the study indicated the existence of a positive medium statistically function between the practice of the female principals of the first circle schools in the province of North Al-Batina of the democratic leadership style and the job satisfaction of the teachers of the first field, where the correlation reached the coefficient r =0.61. Based on the results of the current study, the researcher recommends: maintaining the level of active practice of the democratic leadership style of the female teachers of the first circle schools in North Al-Batina, because of its importance in achieving a good level of job satisfaction, and maintaining the level of high job satisfaction among the teachers of the first field in North Al-Batina, because of its role in achieving.

scholarly journals Tertiary volcanic rocks from Bontekoe Ø, East Greenland

1983 ◽  
Vol 116 ◽  
pp. 1-13
Author(s):  
A Noe-Nygaard ◽  
A.K Pedersen
Keyword(s):  
Volcanic Rocks ◽  
Igneous Rocks ◽  
Geological Survey ◽  
The South ◽  
East Greenland ◽  
The Third ◽  
The North

In East Greenland Tertiary igneous rocks are found from Kap Gustav Holm (66°30'N) in the south to Shannon (75°30'N) in the north. Within this region three areas are covered by plateau basalts; (a) south of Scoresby Sund (700N), (b) far inland on the nunataks at 74°N and (c) along the coast between 73° and 75°30'N. Bontekoe ø belongs to the third region (fig. 1). The geology of this part of East Greenland is largely known from the activities of Lauge Koch's expeditions during which, curiously enough, the areas dominated by Tertiary volcanism were almost neglected. To remedy this the Geological Survey of Greenland supported some reconnaissance work that was carried out in connection with other geological activity in the region over the last few years. Results of this work were given by NoeNygaard & Pedersen (1974), Upton & Emeleus (1977), Hald (1978), Brooks et al. (1979) and Upton et al. (1980, 1982, in press).

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