Le volcan sous-marin d'age acadien de Sidi-Said-Maachou (Maroc occidental)

1956 ◽  
Vol S6-VI (4-5) ◽  
pp. 559-574 ◽  
Author(s):  
Marcel Gigout
Keyword(s):  
Deep Water ◽  
Volcanic Rocks ◽  
Submarine Volcano ◽  
Pyroclastic Material ◽  
Plateau Region ◽  
Basic Lava ◽  
Maroc Occidental

Abstract At three localities in the Sidi-Saied-Maachou area, a complex of volcanic rocks has been identified in the thick, otherwise uniform series of Acadian (Cambrian) green schists of the plateau region of Morocco, which is considered to represent a submarine volcano. Purplish schists, layers of organic limestone, and pyroclastic material, laid down in deep water, are cut by vertical dikes which fed sills and submarine flows of basic lava. The eruption was calm, resembling, on a much smaller scale, the emplacement of greenstones in geosynclines.

Seismic expression and geomorphology of igneous bodies: A Taranaki Basin, New Zealand, case study

2017 ◽  
Vol 5 (3) ◽  
pp. SK121-SK140 ◽  
Author(s):  
Lennon Infante-Paez ◽  
Kurt J. Marfurt
Keyword(s):  
New Zealand ◽  
Volcanic Rocks ◽  
Pyroclastic Flows ◽  
3D Seismic ◽  
Submarine Volcano ◽  
Self Organizing Maps ◽  
Seismic Geomorphology ◽  
Carbonate Buildups ◽  
Oil Flow

Very little research has been done on volcanic rocks by the oil industry due to the misconception that these rocks cannot be “good reservoirs.” However, in the past two decades, significant quantities of hydrocarbons have been produced from volcanic rocks in China, New Zealand, and Argentina. In frontier basins, volcanic piles are sometimes misinterpreted to be hydrocarbon anomalies and/or carbonate buildups. Unlike clastic and carbonate systems, the 3D seismic geomorphology of igneous systems is only partially documented. We have integrated 3D seismic data, well logs, well reports, core data, and clustering techniques such as self-organizing maps to map two distinct facies (pyroclastic and lava flows), within a Miocene submarine volcano in the Taranaki Basin, New Zealand. Three wells; Kora-1–3 drilled the pyroclastic facies within the volcano encountering evidence of a petroleum system, whereas the Kora-4 well drilled the lava-flow facies, which was barren of hydrocarbons. By integrating results from geochemistry and basin modeling reports prepared for Crown Mineral, New Zealand, we concluded that the reason that Kora-4 was dry was due to a lack of source charge — not to the absence of reservoir quality. Moreover, the Kora-1 well drilled a thick sequence (>[Formula: see text]) of pyroclastic flows in this submarine volcano by chance and found high peaks of gas in the mudlogs near the top 25 m of this sequence. A long-term test in this upper volcanic section resulted in 32 API oil flow of 668 barrels of oil per day for 254 h — a result that challenges the misconception that volcanic rocks cannot be good reservoirs.

Depositional Palaeoenvironment and Models of the Eocene Lacustrine Source Rocks in the Northern South China Sea

2021 ◽  
Author(s):  
Niubin Zhao
Keyword(s):  
Organic Matter ◽  
South China Sea ◽  
South China ◽  
Deep Water ◽  
Northern South China Sea ◽  
Volcanic Rocks ◽  
Source Rocks ◽  
High Quality ◽  
Reducing Conditions ◽  
Parent Rocks

<p>      Element geochemical analysis of 94 ditch cutting samples of the shale source rock from the Wenchang Formation in the Zhuyi sub-basin and the Liushagang Formation in the Weixinan sub-basin was conducted to determine their palaeoenvironment and main controlling factors and to further establish development models. The results indicate that freshwater and a warm and humid climate were characteristics of the depositional palaeoenvironment between Wenchang and Liushagang formations. During the deposition of Wenchang Formation, the parent rocks mainly consisted of felsic volcanic rocks, the water was characterized by a high palaeoproductivity, shallow-deep water depths, and weakly reducing conditions, whereas during the deposition of Liushagang Formation, the parent rocks mainly consisted of mafic volcanic rocks,<strong> </strong>and the palaeoproductivity, palaeowater depth, and reducing conditions of the water were better than during the deposition of<strong> </strong>Wenchang Formation. The formation of high-quality source rocks in the Liushagang Formation were mainly controlled by two factors: (1) the mafic igneous rock provenance and strong weathering provided macronutrients (e.g. P, Fe) for water; (2) high palaeoproductivity provided the source of organic matter, which played a much important role than preservation condition of organic matter. For Wenchang Formation, the good preservation of organic matter which was created by the reducing environment in deep water was also necessary. Accordingly, two models were briefly summarized: a productivity and preservation model for the Wenchang Formation source rocks and a productivity model for the Liushagang Formation source rocks, both of them can develop high-quality source rocks, but the source rock quality of the former were lower than of the latter, this was mainly attributed to the difference in the nutrients and palaeoproductivity. This study provides valuable guidance for oil and gas exploration in the northern South China Sea and the study of lacustrine source rocks in other areas.</p>

Pearya: a composite terrane with Caledonian affinities in northern Ellesmere Island

1987 ◽  
Vol 24 (2) ◽  
pp. 224-245 ◽  
Author(s):  
H. P. Trettin
Keyword(s):  
Deep Water ◽  
Volcanic Rocks ◽  
Volcanic Belt ◽  
Ellesmere Island ◽  
Mobile Belt ◽  
Lower Paleozoic ◽  
Water Basin ◽  
Middle Ordovician ◽  
Angular Unconformity ◽  
Deep Water Basin

In Ellesmere Island, the Canadian Shield and Arctic Platform are flanked on the northwest by the lower Paleozoic Franklinian mobile belt, which comprises an unstable shelf (miogeocline) and a deep-water basin, divisible into an inner sedimentary belt and an outer sedimentary–volcanic belt. Both are tied to the shelf by interlocking facies changes, but additional exotic units may be present in the outer belt.Pearya, bordering the deep-water basin on the northwest, is divisible into four successions. Succession I comprises sedimentary and(?) volcanic rocks, deformed, metamorphosed to amphibolite grade, and intruded by granitic plutons at 1.0–1.1 Ga. Succession II consists mainly of platformal sediments (carbonates, quartzite, mudrock), with smaller proportions of mafic and siliceous volcanics, diamictite, and chert ranging in age from Late Proterozoic (Hadrynian) to latest Cambrian or Early Ordovician. Its concealed contact with succession I is tentatively interpreted as an angular unconformity. Succession III (Lower to Middle Ordovician?) includes arc-type and ocean-floor volcanics, chert, mudrock, and carbonates and is associated with fault slices of Lower Ordovician (Arenig) ultramafic–mafic complexes–possibly dismembered ophiolites. The faulted contact of succession III and the ultramafics with succession II is unconformably overlapped by succession IV, 7–8 km of volcanic and sedimentary rocks ranging in age from late Middle Ordovician (Blackriverian = early Caradoc) to Late Silurian (late Ludlow?). The angular unconformity at the base of succession IV represents the early Middle Ordovician (Llandeilo–Llanvirn) M'Clintock Orogeny, which was accompanied by metamorphism up to amphibolite grade and granitic plutonism. Pearya is related to the Appalachian–Caledonian mobile belt by the Grenville age of its basement, the age of its ultramafic–mafic complexes, and evidence for a Middle Ordovician orogeny, comparable in age and character to the Taconic. By contrast, the Franklinian mobile belt has a Lower Proterozoic (Aphebian) – Archean basement and was not deformed in the Ordovician. Stratigraphic–structural evidence suggests that Pearya was transported by sinistral strike slip as three or more slices and accreted to the Franklinian deep-water basin in the Late Silurian under intense deformation. The inferred sinistral motion is compatible with derivation from the northern Caledonides.

Structure of the Dingle Peninsula, SW Ireland: evidence for the nature and timing of Caledonian, Acadian and Variscan tectonics

2014 ◽  
Vol 152 (2) ◽  
pp. 242-268 ◽  
Author(s):  
S.P. Todd
Keyword(s):  
Deep Water ◽  
Volcanic Rocks ◽  
Fault Zones ◽  
Early Devonian ◽  
Shallow Marine ◽  
Red Sandstone ◽  
Early Ordovician ◽  
The North ◽  
Tectonic History ◽  
Extensional Structures

AbstractThe Palaeozoic rocks of the Dingle Peninsula provide a record of the evolution of the Caledonides, Acadides and Variscides. The succession ranges from Early Ordovician deep-water sediments, through Silurian shallow marine to non-marine sediments and volcanic rocks to an Old Red Sandstone (ORS) succession topped by Carboniferous marine shales. Comparison of structural styles in the unconformity-bounded groups, together with a detailed analysis of fault zones, allows the tectonic history to be deduced. The older rocks record Caledonian processes on the margin of Avalonia during Early Ordovician time and convergence then soft collision with Laurentia during Silurian time. The Dingle Basin was developed during the late Silurian – Early Devonian transtension in the Iapetus suture zone and was inverted in the latest Emsian Acadian orogenic episode. Post-Dingle Group ORS groups in the north of the peninsula were deposited in a syn-rift footwall block to the main Munster Basin. The Acadian transpressional and Munster Basin extensional structures were reactivated or overprinted in the Variscan deformation such that Acadian folds are transected by Variscan cleavage in both plan and vertical views. After Iapetus closure, changes in the tectonic regime are believed to be a result of adjustments in the geometry of subduction of the Rheic Ocean.

scholarly journals INDICATION OF HYDROTHERMAL ALTERATION ACTIVITIES BASED ON PETROGRAPHY OF VOLCANIC ROCKS IN ABANG KOMBA SUBMARINE VOLCANO, EAST FLORES SEA

2016 ◽  
Vol 29 (2) ◽  
pp. 91
Author(s):  
Lili Sarmili ◽  
Johanes Hutabarat
Keyword(s):  
Clay Minerals ◽  
Hydrothermal Alteration ◽  
Partial Oxidation ◽  
Volcanic Rocks ◽  
Hydrothermal Solutions ◽  
Submarine Volcano ◽  
Petrographic Analyses ◽  
Ore Minerals ◽  
Mineral Alteration

The presence of mineral alteration or secondary processes to rocks on submarine volcano of Abang Komba was caused by an introduction of hydrothermal solutions. Those are indicated by the presence of a resembly of minerals alteration seen in their petrographic analyses. They are characterized by replacement partially surrounding of plagioclase phenocrysts, partially replacing plagioclase by sericite, carbonate and clay minerals. The replacement of pyroxene partly by chlorite, and the presence of albitisation (secondary albite) contained in fine rectangular plagioclase sized. Other fitures occasionally observed by the presence of partial oxidation of ore minerals and the presence of quartz, and epidote as an alteration from plagioclase and pyroxene. Keywords : alteration, resembly of minerals alteration, oxidation, submarine vulcano of Abang Komba. Gejala alterasi atau proses-proses sekunder yang terjadi pada batuan di gunung bawah laut Abang Komba adalah disebabkan oleh introduksi larutan hidrotermal. Semua ini ditunjukkan dengan kehadiran kumpulan mineral ubahan yang terlihat dalam sayatan batuan. Kumpulan mineral ini dicirikan dengan adanya penggantian sebagian yang mengelilingi fenokris plagioklas, penggantian sebagian plagioklas oleh serisit, karbonat dan mineral lempung. Penggantian sebagian piroksen oleh klorit, dan adanya gejala albitisasi (albit sekunder) yang terdapat pada plagioklas berbentuk balokan yang berukuran halus. Gejala lainnya yang kadang-kadang teramati adanya oksidasi sebagian dari mineral bijih dan hadirnya kuarsa, serta epidot sebagai hasil ubahan plagioklas dan piroksen. Kata kunci : alterasi, kumpulan mineral ubahan, oksidasi, gunung bawahlaut Abang Komba.

scholarly journals Терригенное лавинное осадконакопление на примере пермских толщ Охотского и Аян-Юряхского бассейнов (Северо-Восток Азии)

2020 ◽  
pp. 3-12
Author(s):  
A. S. Biakov ◽  
◽  
I. L. Vedernikov ◽  
◽  
Keyword(s):  
Deep Water ◽  
Northeast Asia ◽  
Outer Part ◽  
Global Scale ◽  
Pyroclastic Material ◽  
Coastal Marine ◽  
Okhotsk Massif ◽  
Three Stages ◽  
Northeast Asian ◽  
Almost All

Terrigenous avalanche sedimentation in Northeast Asia is considered on the example of the Permian strata of the Okhotsk and Ayan-Yuryakh basins. These deposits form a complicated sedimentary complex undergoing regular changes in the direction from the southwest (from the Okhotsk massif) to the northeast (to the Ayan-Yuryakh anticlinorium) - from continental and coastal-marine environments to deep-water, corresponding to the conditions of the foot of the continental slope. An important specific feature of this basins is the widespread development of deep-water deposits, primarily of various types of gravitites, among which facies of proximal and distal turbidites, grain and clay flows, and diamictites (debrites) can be distinguished. The facies of nepheloidites and disturbed-bedded deep-water siltstones also play a significant role. Shallower sediments are less widespread and were formed within the shelf of the Okhotsk massif. They are represented by facies of coastal sandstones, sandstones and siltstones of the inner part of the shelf and siltstones of the outer part of the shelf. Almost all types of rocks contain one or another fraction of pyroclastic material, the amount of which increases with approaching the Okhotsk massif, where some probable centers of eruptions of the Okhotsk-Taigonos volcanic arc were located. In the evolution of the basins under consideration, the general stages in the development of the entire system of northeast Asian basins are clearly established, which was obviously determined by reasons of a global scale. The first three stages correspond to the regional superhorizons (Munugudzhakian, Dzhigdalian, and Omolonian), the last three, to the Gizhigian Horizon and subhorizons of the Khivachian Horizon).

Crustal structure beneath oceanic islands

1954 ◽  
Vol 222 (1150) ◽  
pp. 361-387 ◽  
Keyword(s):  
Crustal Structure ◽  
Deep Water ◽  
Seismic Waves ◽  
Volcanic Rocks ◽  
Oceanic Islands ◽  
Lava Flows ◽  
Basaltic Lava ◽  
Sea Floor ◽  
Isostatic Adjustment ◽  
Gravity And Magnetic

The difficulties and ambiguities in the interpretation of seismic, gravity and magnetic observations are discussed. The results obtained near the islands of Oahu, Bermuda and Bikini are summarized. On all these islands there is evidence of the presence of basaltic lava flows. Gravity and magnetic surveys are incomplete but are sufficient to show that there are considerable anomalies probably associated with the volcanic rocks. The velocity of compressional seismic waves in the coral cap is 2·5 to 3·1 km/s, whilst the volcanic rocks give 4 to 5½ km/s. Measurements in the surrounding deep water give a velocity of about 8·1 km/s at a depth of 10 km near Bermuda, and 13 km near Bikini. Over this velocities of 6·9 km/s (Bermuda) and 6·5 km/s (Bikini) were found. All the results appear to be consistent with the view that the islands have a volcanic core which constitutes a load on the sea floor. This load and the necessity of filling the space vacated by the lava causes a gradual sinking of the crust to produce a regional isostatic adjustment.

Benthic foraminiferal zonation in deep-water carbonate platform margin environments, northern Little Bahama Bank

1988 ◽  
Vol 62 (01) ◽  
pp. 1-8 ◽  
Author(s):  
Ronald E. Martin
Keyword(s):  
Deep Water ◽  
Benthic Foraminifera ◽  
Carbonate Platform ◽  
Sedimentary Facies ◽  
Depositional Environments ◽  
Near Surface ◽  
Sediment Gravity Flows ◽  
Gravity Flows ◽  
Platform Margin ◽  
Water Carbonate

The utility of benthic foraminifera in bathymetric interpretation of clastic depositional environments is well established. In contrast, bathymetric distribution of benthic foraminifera in deep-water carbonate environments has been largely neglected. Approximately 260 species and morphotypes of benthic foraminifera were identified from 12 piston core tops and grab samples collected along two traverses 25 km apart across the northern windward margin of Little Bahama Bank at depths of 275-1,135 m. Certain species and operational taxonomic groups of benthic foraminifera correspond to major near-surface sedimentary facies of the windward margin of Little Bahama Bank and serve as reliable depth indicators. Globocassidulina subglobosa, Cibicides rugosus, and Cibicides wuellerstorfi are all reliable depth indicators, being most abundant at depths >1,000 m, and are found in lower slope periplatform aprons, which are primarily comprised of sediment gravity flows. Reef-dwelling peneroplids and soritids (suborder Miliolina) and rotaliines (suborder Rotaliina) are most abundant at depths <300 m, reflecting downslope bottom transport in proximity to bank-margin reefs. Small miliolines, rosalinids, and discorbids are abundant in periplatform ooze at depths <300 m and are winnowed from the carbonate platform. Increased variation in assemblage diversity below 900 m reflects mixing of shallow- and deep-water species by sediment gravity flows.

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.

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