Ophiolitic mélange and its significance in the Fleur de Lys Supergroup, northern Appalachians

1977 ◽  
Vol 14 (5) ◽  
pp. 987-1003 ◽  
Author(s):  
Harold Williams
Keyword(s):  
Continental Margin ◽  
Full Range ◽  
Sedimentary Rocks ◽  
Ultramafic Rocks ◽  
Eastern North America ◽  
Plate Boundaries ◽  
Polyphase Deformation ◽  
Ophiolitic Mélange ◽  
Ophiolite Suite ◽  
Clastic Sedimentary

Ophiolitic mélange consists of a chaotic mixture of sedimentary rocks and igneous rocks derived from the ophiolite suite of rock units. Its formation involves surficial mass wastage, gravity sliding, and tectonism at consuming plate boundaries. Most worldwide examples relate to ophiolite obduction and the destruction of stable continental margins.The Fleur de Lys Supergroup of the northern Appalachians consists of polydeformed and metamorphosed, mainly clastic sedimentary rocks that accumulated at the Hadrynian to early Paleozoic stable continental margin of eastern North America. Greenschists at or near the top of the succession in the east (Birchy Complex) contain zones of typical ophiolitic mélange. These contain large blocks of serpentinized ultramafic rocks, actinolite–fuchsite alterations of smaller ultramafic blocks, altered gabbro, a variety of clastic sedimentary blocks, and marble. All of the rocks are multideformed and metamorphosed so that the mélange was subjected to the full range of Fleur de Lys deformations.The presence of polydeformed and metamorphosed ophiolitic mélange in the Fleur de Lys Supergroup implies an early disruption or imbrication of its rock units. This disruption and mélange formation are interpreted to be related to transport of ophiolite complexes such as the Bay of Islands Complex across an initially undisturbed continental rise prism, the Fleur de Lys Supergroup. Later polyphase deformation and metamorphism of the Fleur de Lys Supergroup are possible results of continued structural submergence and telescoping of the continental margin beneath a thick cover of transported ophiolite rock units.

Structural Succession, Nomenclature, and Interpretation of Transported Rocks in Western Newfoundland

1975 ◽  
Vol 12 (11) ◽  
pp. 1874-1894 ◽  
Author(s):  
Harold Williams
Keyword(s):  
North America ◽  
Subduction Zone ◽  
Continental Margin ◽  
North American ◽  
Sedimentary Rocks ◽  
Eastern North America ◽  
Stacking Order ◽  
Ophiolite Suite ◽  
Plutonic Rocks

The Humber Arm and Hare Bay Allochthons of Western Newfoundland are made up of a variety of sedimentary rocks and volcanic and plutonic rocks that originated toward the east and record the evolution and destruction of the ancient continental margin of Eastern North America. Five contrasting rock assemblages that constitute different structural slices are defined and delineated in the Humber Arm Allochthon. Six contrasting rock assemblages constitute the Hare Bay Allochthon. In each allochthon, the lower structural slices consist of sedimentary rocks and the highest structural slice consists of the ophiolite suite. The stacking order and mode of assembly indicate that progressively higher slices travelled increasingly greater distances, so that their present vertical superposition represents a former west-to-east juxtaposition.Most of the transported rocks have direct lithic correlatives in central Newfoundland. These occur west of the Dunnage Mélange, so that if the Dunnage marks the vestige of a North American subduction zone, then all the transported sequences once lay between a continental margin and a nearby oceanic trench.

The dynamothermal aureole of the Bay of Islands ophiolite suite

1979 ◽  
Vol 16 (11) ◽  
pp. 2086-2101 ◽  
Author(s):  
John Malpas
Keyword(s):  
Heat Flux ◽  
North America ◽  
Volcanic Rocks ◽  
High Heat ◽  
Eastern North America ◽  
High Heat Flux ◽  
Polyphase Deformation ◽  
Middle Ordovician ◽  
Ophiolite Suite ◽  
Chemical Studies

The Bay of Islands ophiolite suite was displaced from an oceanic environment and emplaced upon the continental margin of Eastern North America during Early to Middle Ordovician times. The displacement tectonics produced a dynamothermal aureole that is found at the stratigraphic base of each ophiolite thrust slice. Structural and chemical studies of the aureole rocks indicate that they were produced by polyphase deformation of tuffaceous sediments and volcanic rocks under conditions of relatively high heat flux. Calculations show that this heat could not all have been produced by friction, but that the overriding ophiolite slab must have been hot. High geothermal gradients necessary to satisfy such a model are to be expected only in certain oceanic environments.

scholarly journals The provenance of Jurassic and Lower Cretaceous clastic sediments offshore southwestern Nova Scotia

2017 ◽  
Vol 54 (1) ◽  
pp. 33-51 ◽  
Author(s):  
Dan-Cezar Dutuc ◽  
Georgia Pe-Piper ◽  
David J.W. Piper
Keyword(s):  
Nova Scotia ◽  
Deep Water ◽  
Lower Cretaceous ◽  
Middle Jurassic ◽  
Sedimentary Rocks ◽  
Petroleum Exploration ◽  
Ultramafic Rocks ◽  
Meguma Terrane ◽  
Clastic Sedimentary ◽  
Fundy Basin

Jurassic and Cretaceous sandstones in the Shelburne subbasin and Fundy Basin offshore Nova Scotia, are poorly known but are of current interest for petroleum exploration. The goal of this study is to determine the provenance of sandstones and shales, which will contribute to a better understanding of regional tectonics and paleogeography in the study area. Mineral and lithic clast chemistry was determined from samples from conventional cores and cuttings from exploration wells, using scanning electron microscopy and an electron microprobe. Whole-rock geochemical composition of shales was used to test the hypotheses regarding provenance of Mesozoic clastic sedimentary rocks in the SW Scotian Basin. Lower Jurassic clastic sedimentary rocks in the Fundy Basin contain magnetite, biotite, and chlorite, suggesting local supply from the North Mountain Basalt and Meguma Terrane, whereas pyrope and anthophyllite suggest small supply from distant sources. In the SW Scotian Basin, detrital minerals, lithic clasts, and shale geochemistry from Middle Jurassic to Early Cretaceous indicate a predominant Meguma Terrane source and transport by local rivers. Rare spinel and garnet grains of meta-ultramafic rocks, only in the Middle Jurassic at the Mohawk B-93 well, suggest minor supply from the rising Labrador rift, via the same river that transported distant sediments to the Fundy Basin. Lower Cretaceous sandstones from the Mohican I-100 well contain minor garnet, spinel, and tourmaline from meta-ultramafic rocks, characteristic of sediment supplied to the central Scotian Basin at that time. The dominant Meguma Terrane provenance precludes thick deep-water sandstones in the eastern part of the Shelburne subbasin, but the evidence of Middle Jurassic distant river supply through the Fundy Basin is encouraging for deep-water reservoir quality in the western part.

Tectonic setting of Avalonian volcanic and Plutonic rocks in the Caledonian Highlands, southern New Brunswick, Canada

1996 ◽  
Vol 33 (2) ◽  
pp. 156-168 ◽  
Author(s):  
S. M. Barr ◽  
C. E. White
Keyword(s):  
New Brunswick ◽  
Subduction Zone ◽  
Continental Margin ◽  
Tectonic Setting ◽  
Sedimentary Rocks ◽  
Igneous Activity ◽  
Appalachian Orogen ◽  
Group Form ◽  
Plutonic Rocks ◽  
Clastic Sedimentary

The Caledonian Highlands of southern New Brunswick consist of Late Proterozoic to Cambrian rocks generally considered typical of the Avalon terrane of the northern Appalachian Orogen. Mainly tuffaceous volcanic and sedimentary rocks of the Broad River Group and cogenetic dioritic to granitic plutons with ages ca. 620 Ma form most of the eastern Caledonian Highlands. They have petrological features indicative of origin in a continental margin subduction zone. Significantly younger ca. 560–550 Ma dacitic to rhyolitic lapilli tuffs and flows, laminated tuffaceous siltstone, basaltic and rhyolitic flows, and clastic sedimentary rocks of the Coldbrook Group form most of the western highlands, and occur locally throughout the highlands. The mainly tuffaceous lower part of the group has been intruded by gabbroic and syenogranitic plutons that are interpreted to be cogenetic with basaltic and rhyolitic flows in the upper part of the group. This voluminous subaerial magmatism may have formed during postorogenic extension in the earlier ca. 620 Ma subduction zone complex represented by the Broad River Group and associated plutons. This tectono-magmatic model differs from other interpretations that related most of the igneous units to ca. 630–600 Ma subduction, and did not recognize the importance of ca. 560–550 Ma magmatism. The ca 620 Ma subduction-related volcanic and plutonic rocks of the Caledonian Highlands are comparable to units in other parts of the Avalon terrane, but voluminous ca. 560–550 Ma igneous activity like that represented by the Coldbrook Group and related plutons has not been documented yet in other Avalonian areas.

A suite of alkali basalts and gabbros associated with the Hare Bay Allochthon of western Newfoundland

1977 ◽  
Vol 14 (3) ◽  
pp. 346-356 ◽  
Author(s):  
R. A. Jamieson
Keyword(s):  
Oceanic Crust ◽  
Continental Margin ◽  
Upper Mantle ◽  
Ultramafic Rocks ◽  
Alkali Basalts ◽  
Crust And Upper Mantle ◽  
Bay Area ◽  
Close Proximity ◽  
Thrust Sheets

The Hare Bay Allochthon of northwestern Newfoundland consists of a series of sedimentary, volcanic, metamorphic, and ultramafic rocks which was emplaced over a Cambro-Ordovician continental margin as several thrust sheets. It probably represents a continental margin sequence overridden by oceanic crust and upper mantle. The Partridge Point gabbro, Cape Onion volcanics, and Ireland Point Volcanics, which now occur in the Maiden Point, Cape Onion, and St. Anthony tectonic slices respectively, appear to be closely related on petrographic and chemical grounds. Olivine, titanaugite, kaersutite, and plagioclase indicate that these rocks formed as a single suite of hydrous alkali basalts, possibly as part of a seamount near a continental margin. This relationship provides a link between the lower sedimentary and the upper igneous-metamorphic structural slices of the allochthon and implies that most of the transported rocks in the Hare Bay area evolved in close proximity to each other.

Factors dominating deterioration of clastic sedimentary rocks

2011 ◽  
pp. 939-944
Author(s):  
P Chan ◽  
S Lyu ◽  
T Wang ◽  
F Jeng ◽  
T Ueng
Keyword(s):  
Sedimentary Rocks ◽  
Clastic Sedimentary

scholarly journals GEODYNAMICS AND MAGMATISM OF THE PACIFIC-TYPE TRANSFORM MARGINS. ASPECTS AND DISCRIMINANT DIAGRAMS

2021 ◽  
pp. 3-24
Author(s):  
A.V. Grebennikov ◽  
◽  
A.I. Khanchuk ◽  
Keyword(s):  
Continental Margin ◽  
Tectonic Setting ◽  
Island Arc ◽  
Igneous Rocks ◽  
High Alumina ◽  
Plate Boundaries ◽  
Spreading Ridge ◽  
Convergent Margins ◽  
Oceanic Plate ◽  
Plate Movement

Transform margins represent lithospheric plate boundaries with horizontal sliding of oceanic plate, which in time and space replaced the subduction related convergent margins. This happened due to: spreading ridge–trench intersection (California; Queen Charlotte–Northern Cordilleran, West of the Antarctic Peninsula, and probably the Late Miocene–Pleistocene Southernmost South America) or ridge death along continental margin (Baja California); change in the direction of oceanic plate movement (Western Aleutian–Komandorsk; Southernmost tip of the Andes); and island arc-continent collision (New Guinea Island). Post-subduction magmatism is related to a slab window that resulted either from the spreading ridge collision (subduction) with a continental margin or slab tear formation, or slab break-off after subduction cessation due to other reasons. Igneous magmatic series formed in consequence of these events show diversity of tholeiitic (sub-alkaline), alkaline or calc-alkaline, high-alumina and adakitic rocks. The comprehensive geochemical dataset (more than 2400 analyses) on igneous rocks of the model transform and convergent geodynamic settings allowed to substantiate the most informative triple diagrams for the petrogenic oxides TiO2 × 10 – Fe2O3Tot – MgO and trace elements Nb – La– Yb. Mostly approved for the rock compositions with SiO2 < 63 wt. %, the new plots are capable of distinguishing igneous rocks formed above zones of subduction at an island arc and continental margin (related to convergent margins), from those formed in the tectonic setting of transform margins along continents or island arcs.

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