Cape Ray Research Articles

U.S. To Zap Syria’s Chemical WEapons

An unprecedented mission to destroy Syria’s lethal chemical warfare agents and precursors at sea is set to move into a new phase this month aboard a 22,000-ton U.S. cargo ship. The MV Cape Ray is the centerpiece in the complex international plan to eliminate Syria’s chemical weapons program. Built in 1977, the 648-foot vessel has been used to transport everything from components of oil rigs to military vehicles. As the Cape Ray departed the Norfolk Naval Shipyard on Jan. 27, Defense Secretary Chuck Hagel hailed the historic mission. “You are about to accomplish something no one has tried,” Hagel told the ship’s crew members. “You will be destroying, at sea, one of the world’s largest stockpiles of chemical weapons and helping make a safer world.” The destruction process is part of an agreement with the Syrian government to turn over its weapons for destruction by June 30. Under the United ...

Structural evolution of a major fault zone: the Cape Ray Fault Zone, southwestern Newfoundland, Canada

The Cape Ray Fault Zone is a major Paleozoic structure in southwestern Newfoundland, and occurs at or close to the boundary between two major continental blocks, Laurentia and Avalonia. A detailed structural analysis demonstrates that the fault records early reverse-sinistral thrusting of the Grand Bay Complex at amphibolite grade (D2), followed by a protracted event (D3) characterized by reverse-dextral thrusting of the Grand Bay Complex rocks on top of the supracrustal rocks of the Windsor Point Group and retrogression to greenschist facies, as well as a pre-384 Ma orogen-parallel dextral transcurrent mylonite (D4) during the later stages of the collision. Regional-scale strain partitioning induced heterogeneity of strain both along and across the strike of the Cape Ray Fault Zone. The east–west-oriented segment of the Cape Ray Fault Zone is a tear fault that accommodated differential displacement along the length of the fault. Later stages of the deformation include post-384 Ma sinistral transcurrent reactivation of the dextral mylonite and extension. The reverse-sinistral thrusting and the reverse-dextral motion occurred between 415 and 386 Ma and correspond to the two-phase Acadian orogeny recognized at the scale of the orogen and believed to be related to collision between Laurentia and Avalonia. The Cape Ray Fault Zone preserves evidence of large-scale geodynamic processes affecting rocks where the kinematics and the timing are well constrained.

New insights into the Appalachian Orogen from geology and geochronology along the Cape Ray fault zone, southwest Newfoundland

Reverse-oblique overthrusting of high-grade Port aux Basques Gneiss over the lower-grade, supracrustal Windsor Point Group along the Cape Ray fault zone occurred during late Silurian to early Devonian time and is attributed to major oblique collision between Gondwanan and Laurentian continental blocks. New U-Pb zircon, 40 Ar/ 39 Ar, and K/Ar data limit the timing of this orogenic event. The megacrystic granitic phase of the Cape Ray Igneous Complex and the Cape Ray tonalite have been dated at 488 ± 3 Ma and 469 ± 2 Ma, respectively. A black rhyolite from the Windsor Point Group yielded an Ordovician age (453 +5/−4 Ma). A pretectonic gabbro sill within the Windsor Point Group, dated at 424 +4/−3 Ma, is cut by the Windowglass Hill granite dated at 424 ± 2 Ma. Synkinematic hornblende and biotite from the Grand Bay Complex mylonites of the Port aux Basques Gneiss have 40 Ar/ 39 Ar ages of 407 ± 4 Ma and 403 ± 4 Ma, respectively, which is indicative of a late Silurian–early Devonian age for the amphibolite grade deformation. These ages are compatible with a previously determined 415 Ma monazite age, interpreted as the time of peak metamorphism in the Port aux Basques Gneiss, and suggests rapid exhumation. The east-west flexure of the Cape Ray fault zone represents a tear fault accommodating differential shortening between the Cape Ray fault zone and the correlative fault system in central Newfoundland. Mid-Devonian granites (386 ± 3, 384 ± 2 Ma) intervene between the thrusting events and a younger sinistral transcurrent movement. This deformation and magmatic history can be correlated throughout the northern Appalachians along other major fault boundaries.

Geology, geochemistry and geochronology of a taconic batholith, southwestern Newfoundland

ABSTRACTFoliated to massive hornblende and biotite-bearing tonalite, trondhjemite and granodiorite comprise a terrane of batholithic dimensions in southwestern to central Newfoundland. These rocks intrude and include Ordovician ophiolite fragments and metasedimentary rocks of Fleur de Lys type, and are cut by a suite of Silurian gabbro-diorite and norite and Siluro-Devonian (?) granite intrusions.A U/Pb (zircon, sphene) age of 456 ± 3 Ma (2σ) and a K/Ar (hornblende) age of 455 ± 14 Ma (previously reported) for a representative least-deformed tonalite of the Southwest Brook Complex indicate that it crystallised and cooled in Caradoc time. A less precise U/Pb (zircon) age of 428 ± 41 Ma (2σ) is measured for tonalitic Cape Ray Granite in southern Newfoundland. On discrimination diagrams which use Rb, Nb and Y contents to infer tectonic setting, these rocks fall in the field of volcanic arc granites. The occurrence of zircon cores with average ages of 1430 + 18/–17 and 1541 ± 173 Ma (2σ) also indicate that the magmas formed in part by partial melting of Proterozoic crust, or sediments derived from such crust. It is suggested that the tonalitic magmas were generated during the Taconic Orogeny in an arc: continent collision zone at the ancient margin of eastern North America.Tonalitic rocks in western Newfoundland broadly correlative in age and chemistry with the batholith include the Burlington Granodiorite and Hungry Mountain Complex, as well as allochthonous slices of foliated tonalite emplaced over Ordovician platform carbonates W of Grand Lake.

Displacement history of the Northern Arm Fault, and its bearing on the Post-Taconic evolution of north-central Newfoundland

The Northern Arm Fault is a northeast trending late Paleozoic fault which, together with the Reach and Cape Ray Faults, separates the Exploits and Botwood tectontratigraphic zones of Newfoundland. Kinematic indicators reveal a dextral strike slip sense of motion. Although previous studies have suggested that the Northern Arm-Reach Fault system represents the suture marking the former position of an ocean which closed during the Devonian Acadian Orogeny, the presence of identical pre-Acadian lithologies and similar deformation histories on either side of the fault suggest otherwise. Alternatively, we suggest that the Northern Arm Fault system represents a major wrench zone, which developed within the Taconic- and Acadian-modified margin of North rn America in response to oblique subduction of the oceanic tract between North America and Gondwana. Analysis of Silurian sedimentary and volcanic sequences of the Botwood and Windsor Point Groups, which occur in right-steps along this fault system, suggests that they formed in pull-apart basins during an earlier episode of strike slip faulting. We relate this phase of motion to oblique subduction of the Acadian Ocean beneath North America during the Silurian and early Devonian, leading to the Acadian Orogeny.

Granite-related gold mineralization in the Cape Ray fault zone of southwestern Newfoundland

Two electrum and base metal sulfide-bearing quartz vein deposits occur in an alaskitic granite (the Windowglass Hill Granite) and an intermixed graphite-chlorite-sericite schist unit (the Windsor Point Group), both within the Cape Ray fault zone of southwestern Newfoundland. Wall rocks to the electrum-bearing quartz veins were subjected to potassic alteration and minor enrichment in chalcophile elements. Ore metals in the showings are Au, Ag, Cu, Pb, and Zn, and their distributions resemble those seen in gold-bearing massive sulfide deposits. The minerals present are galena, sphalerite, chalcopyrite, pyrite, electrum, and rare arsenopyrite, all of which are extensively intergrown. Temperatures of ore formation, or equilibration, estimated from arsenopyrite and other sulfide mineral intergrowths appear to be around 300 degrees C. Sulfur isotope ratios indicate that sulfur in the showings is probably of magmatic origin. Pb isotope ratios in galenas from the showings and felsic volcanic members of the Windsor Point Group are similar and have an oceanic crust-mantle isotopic signature. These precious and base metal-bearing quartz veins were deposited by hydrothermal fluids exsolved as a vapor phase from the Windowglass Hill Granite.

Geochronology of Early to Middle Paleozoic Tectonic Development in the Southwest Newfoundland Gander Zone

Southwest Newfoundland's Gander Zone was once considered part of the collided eastern margin of an early Paleozoic Iapetus ocean, distinguished from the rest of the Gander Zone by the extensive exposure of a polydeformed amphibolite to greenschist facies sequence considered Devonian in age, overlying presumed Precambrian basement. It was later found that truly Devonian strata were confined to the Cape Ray Fault system, the local northwestern boundary of the Zone. U-Pb zircon isotopic ages of and on metavolcanic rocks in the upper part of the sequence southeast of the fault system indicate that Ordovician and possibly older rocks underlie the Gander Zone itself. A temporal framework for the three main stages of regional deformation, corresponding to pre-metamorphic recumbent folding and transpression ( and ), is presented using U-Pb and dates of granitoid and metamorphic rocks. ) is bracketed as late Ordovician or Silurian by means of U-Pb zircon isotopic ages on the metavolcanic rocks and a 412 Ma U-Pb minimum age on a post- granitoid intrusion. Spatial domains of contrasting biotite and hornblende cooling ages reflect the and episodes, which led to post-metamorphic cooling following uplift of different segments of the amphibolite facies metamorphic terrane. Early Devonian differential uplift on the Cape Ray Fault in the northeast was associated with and caused rapid post-metamorphic cooling through Ar retention temperatures to yield nearly concordant biotite and hornblende ages between 374 and 388 Ma. Reverse and oblique-slip faulting during produced oblique northwesterly uplift of the still-buried portion of the amphibolite facies terrane against Devonian strata in the southwest part of the Cape Ray Fault zone. Late Devonian to early Carboniferous post-metamorphic cooling in this segment is confirmed by plateau dates of 345-353 Ma for biotite and 361 Ma for hornblende. The Gander Zone as a whole is imprinted with a strong penetrative structural grain similar in pattern to and structures in the southwest Newfoundland Gander Zone. K-Ar mineral dates are likewise earliest Devonian and younger, in contrast to numerous pre-Devonian K-Ar ages in the Humber and the Dunnage Zones. The Gander Zone, already identified as a wide, Acadian ductile shear belt and noted for widely variable metamorphic grade, might represent a mobile zone where coherent relics of the "Iapetus" or prior stages of Appalachian history were exhumed during Devonian orogeny, many after Silurian or earlier tectonic burial.

Tectonic evolution of southwestern Newfoundland as indicated by granitoid petrogenesis

Four granitoid suites are recognized in the region of the Cape Ray Fault Zone of southwestern Newfoundland. The two oldest (Ordovician–Silurian (?)) suites represent partial melts of their enclosing host rocks. The Port aux Basques granite is modelled as a partial melt of the gneissic component of its host, Port aux Basques Complex. The Cape Ray granite forms a dominantly tonalitic terrane derived by partial melting of ophiolitic material. The Red Rocks granite and a megacrystic phase of the Cape Ray granite form coherent lines of geochemical descent from the parental tonalite but show evidence of some continental crust contamination.The Late Devonian Windowglass Hill granite is a subvolcanic equivalent of felsic volcanic rocks in the Windsor Point Group. Both units were derived as partial melts of continental crust.The post-tectonic, Late Devonian to Early Carboniferous Strawberry and Isle aux Morts Brook granites constitute the youngest granitoid suite in the region. These A-type granitoids were derived as partial melts of an underlying depleted granulitic (felsic) crust. The depleted nature of the source may have resulted from previous generation of the Windowglass Hill granite and Windsor Point Group. The only possible protolith for the granulitic source is Precambrian Grenvillian gneiss. The presence of this gneiss beneath the Cape Ray Fault Zone of southwestern Newfoundland implies that the complete series of lithologies is allochthonous.

The geology and structural history of the Cape Ray Fault Zone in southwestern Newfoundland

Structural studies within the Cape Ray Fault Zone, southwestern Newfoundland indicate that three tectonic events (D1 to D3) have deformed all regional lithologic units. These lithologies are distributed as a tonalitic terrain (intrusive into ophiolitic remnants) to the northwest, a central volcanic–sedimentary terrain, and a staurolite–kyanite gneiss terrain to the southeast. D1 produced the dominant northeasterly striking planar fabrics in the host rocks that are axial planar to isoclinal folds. The fold axes parallel a synkinematic mineral elongation lineation. D2 formed open asymmetrical folds with curvilinear fold axes and local crenulation cleavage. The D3 event produced local conjugate kink folds. Radiometric dates on deformed plutons indicate these deformational events were post-369 ± 12 Ma (post-Middle Devonian) and pre-352 ± 6 Ma (pre-Late Carboniferous).The fault was previously interpreted as a "cryptic suture" along which opposed margins of the Iapetus Ocean were juxtaposed. Supposedly this suture was subsequently partially covered by volcanic and sedimentary rocks. The present work indicates that the deformational events that produced the fault zone overprinted all regional lithologies in a similar manner and that the delineating mylonites were the products of ductile simple shear due to intense localized deformation. The fault itself is a large-scale shear zone and is not the end result of intercontinental collision.

The location of the Iapetus Ocean suture in Newfoundland

Brachiopod and trilobite faunal distributions indicate that the Iapetus Ocean was still wide enough to inhibit migration in the Middle and Late Ordovician. The presence of Silurian and Lower Devonian calc-alkaline rocks suggests that ocean crust was still being subducted long after the end of the Ordovician and that the Iapetus Ocean did not finally close in Newfoundland until the Acadian Orogeny. The Reach Fault divides successions containing different Lower Palaeozoic faunas; to the west, typical North American faunas occur in New World Island (Cobb's Arm Limestone), while to the east the rocks of the Gander region appear to have been attached to the Avalon Peninsula, with its European Lower Palaeozoic faunas, since the Early Ordovician. It is concluded that the Reach Fault marks the suture where the Iapetus Ocean closed at the end of the Early Devonian. This line probably extends across Newfoundland to the south of Buchans, and links up with the Cape Ray Fault in the southwest of the island. An Ordovician fauna from the Davidsville Group of the Gander area is illustrated for the first time; it is not clearly definitive of any faunal province.

Ophiolites in south-western Newfoundland

Ophiolite and ophiolite-related rocks have long been recognised in northern and western Newfoundland1,2. The presence of these rocks has, to a great extent, controlled the plate tectonic models developed for the tectonic evolution of the Newfoundland Appalachians. Such models have been extrapolated through south and south central Newfoundland with little geologic control. I describe here the ophiolites in south-western Newfoundland, discuss their relationship to a cryptic suture, the Cape Ray Fault, and evolve an independent model, which I compare with the model developed for northern and western Newfoundland.

Possible Cryptic Suture in South-west Newfoundland

THE concept of an important fault, the Cabot Fault, cutting across western Newfoundland was proposed by Wilson1 who interpreted it as a great sinistral fault and correlated it with the Great Glen Fault system in Scotland. There is, however, a second large fault in south-west Newfoundland, the Cape Ray Fault, the importance of which has previously been unrecognized. This fault separates two entirely different pre-Ordovician gneissic terrains which, when traced north-eastwards from Port aux Basques (Fig. 1) form the eastern and western margins of the Newfoundland Central Mobile Belt. This belt contains Lower Ordovician rocks in its central part which are interpreted as remnants of an old ocean floor, the proto-Atlantic1–5. The Cape Ray Fault thus effectively cuts out this ocean toward the south and juxtaposes its eastern and western margins. It may therefore represent a cryptic suture along which complete closure of the proto-Atlantic took place.