Correlation of Major Aphebian Rock Units in the Northeastern Canadian Shield

1972 ◽  
Vol 9 (12) ◽  
pp. 1650-1669 ◽  
Author(s):  
G. D. Jackson ◽  
F. C. Taylor
Keyword(s):  
Regional Metamorphism ◽  
Volcanic Rocks ◽  
Structural Data ◽  
Granulite Facies ◽  
Canadian Shield ◽  
Shelf Zone ◽  
Fold Belt ◽  
Entire Area ◽  
Fold Belts ◽  
Basic Volcanic

Several groups of Aphebian layered rocks in the northeastern Canadian Shield have been correlated because of lithologic and stratigraphic similarities and alignment of groups and structural trends. Most of these layered rocks lie in three distinct fold belts which from south to north have been named the Dorset, Foxe, and the Committee Fold Belts.The widespread occurrence of Aphebian outliers between the fold belts indicates that Aphebian strata probably originally covered the entire area from the Circum–Ungava Geosyncline or Fold Belt east to the Dorset Fold Belt and north to the Committee Fold Belt. The name Baffin Geosyncline is proposed for this depositional zone. Aphebian layered rocks in the two last-named fold belts were probably deposited in marginal mio-eugeosynclinal zones of the main geosyncline and are mainly meta-shale, meta-graywacke, and metamorphosed basic volcanic rocks and associated basic and ultrabasic intrusions. The Aphebian rocks of the Dorset and Foxe Fold Belts were deposited in the central shelf zone of the Baffin Geosyncline and are mainly meta-shale, meta-graywacke, rusty quartz-rich gneiss, marble, and quartzite.The Aphebian layered rocks have been intruded by large granitic plutons and have been metamorphosed to amphibolite and granulite facies of regional metamorphism. Age determinations and structural data indicate that a mid-Aphebian orogeny affected much of the northern part of this region 2000–2200 m.y. ago, and that the whole region was strongly affected by the Hudsonian orogeny.

scholarly journals Structural style and kinematics of the Taihang-Luliangshan fold belt, North China: Implications for the Yanshanian orogeny

Lithosphere ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 767-783 ◽  
Author(s):  
Christopher Clinkscales ◽  
Paul Kapp
Keyword(s):  
North China ◽  
Ordos Basin ◽  
Structural Data ◽  
Upper Jurassic ◽  
Geological Mapping ◽  
Fold Belt ◽  
Lower Paleozoic ◽  
The North ◽  
Structural Style ◽  
Fold Belts

Abstract The Middle–Late Jurassic to earliest Cretaceous fold belts of the Yanshanian orogen in North China remain enigmatic with respect to their coeval deformation histories and possible relationship to the contemporaneous Cordilleran-style margin of eastern Asia. We present geological mapping, structural data, and a >400-km-long, strike-perpendicular balanced cross section for the Taihang-Luliangshan fold belt exposed in the late Cenozoic central Shanxi Rift. The northeast-southwest–trending Taihang-Luliangshan fold belt consists of long-wavelength folds (∼35–110 km) with ∼1–9 km of structural relief cored by Archean and Paleoproterozoic metamorphic and igneous basement rocks. The fold belt accommodated ≥11 km of northwest-southeast shortening between the Taihangshan fault, bounding the North China Plain, in the east and the Ordos Basin in the west. Geological mapping in the Xizhoushan, a northeast-southwest–oriented range within the larger Taihangshan mountain belt, reveals two major basement-cored folds: (1) the Xizhou syncline, with an axial trace that extends for ∼100 km and is characterized by a steep to overturned forelimb consistent with a southeast sense of vergence, and (2) the Hutuo River anticline, which exposes Archean–Paleoproterozoic rocks in its core that are unconformably overlain by shallowly dipping (<∼20°) Lower Paleozoic rocks. In the Luliangshan, Mesozoic structures include the Luliang anticline, the largest recognized anticline in the region, the Ningjing syncline, which preserves a complete section of Paleozoic to Upper Jurassic strata, and the Wuzhai anticline; together, these folds are characterized by a wavelength of ∼45–50 km. Shortening in the Taihang-Luliangshan fold belt is estimated to have occurred between ca. 160 Ma and 135 Ma, based on the age of the youngest deformed Upper Jurassic rocks in the Ningjing syncline, previously published low-temperature thermochronology, and regional correlations to better-studied Yanshanian fold belts. The timing of basement-involved deformation in the Taihang-Luliangshan fold belt, which formed >1000 km from the nearest plate margin, corresponds with the termination of arc magmatism along the eastern margin of Asia, implying a potential linkage to the kinematics of the westward-subducting Izanagi (paleo-Pacific) plate.

Mineralogy and genesis of calc-silicates associated with Archean volcanogenic massive sulphide deposits at the Manitouwadge mining camp, Ontario

1992 ◽  
Vol 29 (7) ◽  
pp. 1375-1388 ◽  
Author(s):  
Yuanming Pan ◽  
Michael E. Fleet
Keyword(s):  
Regional Metamorphism ◽  
Spatial Association ◽  
Volcanic Rocks ◽  
Granulite Facies ◽  
Massive Sulphide ◽  
Sea Floor ◽  
Massive Sulphide Deposits ◽  
Volcanogenic Massive Sulphide ◽  
Reducing Environment ◽  
Sulphide Deposits

Skarn-like calc-silicate rocks are reported in spatial association with the Archean Cu–Zn–Ag massive sulphide deposits at the Manitouwadge mining camp, Ontario. Calc-silicates in the footwall of the Willroy mine occur as matrix to breccia fragments of garnetiferous quartzo-feldspathic gneiss and as lenses within garnetiferous quartzo-feldspathic gneiss and are composed of clinopyroxene, garnet, calcic amphiboles, wollastonite, plagioclase, K-feldspar, epidote, quartz, calcite, magnetite, and minor sulphides. Calc-silicates within the main orebody of the Geco mine are characterized by clinopyroxene, calcic amphiboles (Cl–K-rich hastingsitic and ferro-edenitic hornblende, ferro-edenite (up to 4.7 wt.% Cl); and ferroactinolite (6.7 wt.% MnO)), garnet, epidote (including an epidote rich in rare-earth elements and Cl), calcite, quartz, and abundant sulphides. Calc-silicates within the basal 4/2 Copper Zone of the Geco mine contain garnet, gahnite, sphalerite, ferroactinolite (8.5 wt.% MnO), epidote, quartz, biotite, plagioclase, chlorite, muscovite, K-feldspar, and pyrosmalite (with Mn/(Mn + Fe) ratio ranging from 0.21 to 0.61, and up to 3.9 wt.% Cl). The calc-silicates probably represent metasomatic remobilization of dispersed Ca (and Cl) from sea-floor hydrothermal alteration of mafic to intermediate volcanic rocks and are only indirectly related to the hypothesized syngenetic ore-forming processes for the associated base metal sulphide deposits. The calc-silicates formed initially at about 600 °C and 3–5 kbar (1 kbar = 100 MPa) in a mildly reducing environment (from 1 log unit above to 1 log unit below the fayalite–magnetite–quartz buffer) during the upper-amphibolite- to granulite-facies regional metamorphism and were altered subsequently at lower temperatures (<500 °C).

The petrochemistry of the basic volcanic rocks of the South Connemara Group (Ordovician), western Ireland

1983 ◽  
Vol 120 (2) ◽  
pp. 141-152 ◽  
Author(s):  
P. D. Ryan ◽  
M. D. Max ◽  
T. Kelly
Keyword(s):  
Regional Metamorphism ◽  
Volcanic Rocks ◽  
Major And Trace Elements ◽  
Metamorphic Rocks ◽  
Low Grade ◽  
The South ◽  
Northern Margin ◽  
Southern Side ◽  
Western Ireland ◽  
Basic Volcanic

Summary16 samples of Ordovician basic volcanic rocks of the South Connemara Group, which abut the southern side of the metamorphic rocks of the Connemara massif in western Ireland, have been analysed for both major and trace elements. Although subject to low grade regional metamorphism and subsequently hornfelsed by the Galway Granite (400 Ma), their immobile element contents do not appear to be significantly disturbed. These elements characterise the metabasites of the South Connemara Group as ocean floor basalts having their origins in a marginal basin. The Skird Rocks Fault, separating the South Connemara Group from high grade metamorphic rocks of the Connemara massif, is consequently regarded as the northern margin of the vestiges of the lapetus Ocean which can be traced into, and along, the Southern Uplands Fault.

The Wollaston Lake fold-belt system, Saskatchewan–Manitoba

1968 ◽  
Vol 5 (6) ◽  
pp. 1489-1504 ◽  
Author(s):  
P. L. Money
Keyword(s):  
Regional Metamorphism ◽  
Granitic Rocks ◽  
Metamorphic Rocks ◽  
Intermediate Type ◽  
Fold Belt ◽  
System A ◽  
Fold Belts ◽  
Group A ◽  
Group Form ◽  
Belt System

The Wollaston Lake fold-belt system, a major feature of the Churchill (structural) Province, consists of coalescing fold belts that collectively have been traced for about 400 miles. The fold belts, formed during the Hudsonian orogeny ~1750 million years ago, consist of tightly to isoclinally folded metamorphic and migmatitic rocks. They are bounded mainly by granitic rocks (in the broad sense) that are probably in part younger and in part older. The metamorphic rocks comprising them have been assigned locally to the Daly Lake, Sandfly Lake, or Meyers Lake Groups. The Daly Lake Group (a miogeosynclinal type of assemblage) has an uncertain relationship to the Sandfly Lake Group (eugeosynclinal assemblage); it was probably not deposited contemporaneously with the Meyers Lake Group. The Meyers Lake Group, which has a considerable resemblance to 'stable shelf1 assemblages, although it is less mature, overlies the Sandfly Lake Group, probably unconformably. Metamorphic rocks lithologically similar to those assigned to the Daly Lake Group form most of the fold-belt system. Rocks similar to those assigned to the other groups are of limited extent. The rocks within the fold-belt system have undergone regional metamorphism of the andalusite–sillimanite or low pressure intermediate type and in general now belong to the amphibolite facies. Mineralization within the fold-belt system, consisting of syngenetic (?) sphalerite, galena, and copper minerals, was widespread, but is not yet known to be of economic importance. The most prominent zone of magnetic anomalies in the Precambrian of Saskatchewan coincides in part with the fold-belt system.

Origin of infracrustal (I-type) granite magmas

1988 ◽  
Vol 79 (2-3) ◽  
pp. 71-86 ◽  
Author(s):  
B. W. Chappell ◽  
W. E. Stephens
Keyword(s):  
Partial Melting ◽  
Subduction Zones ◽  
Chemical Weathering ◽  
Volcanic Rocks ◽  
Source Rocks ◽  
Fold Belt ◽  
Small Component ◽  
Lachlan Fold Belt ◽  
Fold Belts ◽  
Type Granite

ABSTRACTI-type granites are produced by partial melting of older igneous rocks that are metaluminous and hence have not undergone any significant amount of chemical weathering. In the Lachlan Fold Belt of southeastern Australia and the Caledonian Fold Belt of Britain and Ireland there was a major magmatic event close to 400 Ma ago involving a massive introduction of heat into the crust. In both areas, that Caledonian-age event produced large volumes of I-type granite and related volcanic rocks. Granites of these two areas are not identical in character but they do show many similarities and are markedly different from many of the granites found in Mesozoic and younger fold belts. These younger, dominantly tonalitic, granites have compositions similar to those of the more felsic volcanic rocks forming at the present time above subduction zones. The Palaeozoic granites show little evidence of such a direct relationship to subduction. Within both the Caledonian and Lachlan belts there are some granites with a composition close to the younger tonalites. A particularly interesting case is that of the Tuross Head Tonalite of the Lachlan Fold Belt, which can be shown to have formed from slightly older source rocks by a process that we refer to as remagmatisation which has caused no significant change in composition. Since remagmatisation has reproduced the former source composition in the younger rocks, the wrong inference would result from the use of that composition to deduce the tectonic conditions at the time of formation of the tonalite. Granites, particularly the more mafic ones, will generally have compositions reflecting the compositions of their source rocks, and attempts to use granite compositions to reconstruct the tectonic environment at the time of formation of the granite may be looking instead at an older event. This is probably also the case for some andesites formed at continental margins.Several arguments can be presented in favour of a general model for the production of I-type granite sources by underplating the crust, so that the source rocks are infracrustal. Such sources may contain a component of subducted sediments with the consequence that some of the compositional characteristics of sedimentary rocks may be present in I-type source rocks and in the granites derived from them. The small bodies of mafic granite and gabbro associated with island arc volcanism have an origin that can be related to the partial melting of subducted oceanic crust or of mantle material overlying such slabs and can be referred to as M-type. These rocks have compositions indistinguishable from those of the related volcanic rocks, except for a small component of cumulative material. The tonalitic I-type granites characteristic of the Cordillera are probably derived from such M-type rocks of basaltic to andesitic composition, which had been underplated beneath the crust. Some of the more mafic tonalites of the Caledonian-age fold belts may also have had a similar origin. More commonly, however, the plutonic rocks of the older belts are granodioritic and these probably represent the products of partial melting of older tonalitic I-type source rocks in the deep crust, these having compositions and origins analogous to the tonalites of the Cordillera. In this way, multiple episodes of partial melting, accompanied by fractionation of the magmas, can produce quite felsic rocks from original source rocks in the mantle or mantle wedge. These are essential processes in the evolution of the crust, since the first stages in this process produce new crust and the later magmatic events redistribute this material vertically without the addition of significant amounts of new crust.

scholarly journals Stratigraphy and structure of the Fiskenæsset Complex, southern West Greenland

1985 ◽  
Vol 150 ◽  
pp. 1-72
Author(s):  
J.S Myers
Keyword(s):  
Volcanic Rocks ◽  
Layered Intrusion ◽  
Granulite Facies ◽  
Thin Layers ◽  
Tectonic Activity ◽  
Gneiss Complex ◽  
Metavolcanic Rocks ◽  
Lithostratigraphic Units ◽  
Basic Volcanic ◽  
Igneous Layering

The Fiskenæsset Complex is a deformed and metamorphosed, sheet-like, layered basic instrusion. It is an exceptionally well-preserved example of a suite of anorthositic rocks which are a widespread, but fragmentary, component of the Archaean gneiss complex of Greenland. In the Fiskenæsset region these rocks can be seen to be part of a single layered intrusion which consists of seven major lithostratigraphic units. In ascending order, these units are the Lower Gabbro (50 m), Ultramafic (40 m), Lower Leucogabbro (50 m), Middle Gabbro (40 m), Upper Leucogabbro (60 m), Anorthosite (250 m) and Upper Gabbro (50 m) Units. The Fiskenæsset Complex crystallised from tholeiitic magmas which were probably emplaced in at least 3 stages. It was intruded into basic volcanic rocks (now amphibolites) and, together with these rocks, was fragmented by the intrusion of granitoid sheets (now gneisses) associated with thrusting 2900-2800 m.y. ago. The Fiskenæsset Complex and metavolcanic rocks occur as thin layers and trains of inclusions within these gneisses which form about 80% of the region. All these rocks were folded together into large recumbent, nappe-like, folds (F1), and then refolded into dome-and-basin interference patterns by two sets of folds with steep axial surfaces at high angles to each other (F2 and F3). Deformation was locally heterogeneous, and all stages can be seen from undeformed to very strongly deformed rocks. Recrystallisation continued in amphibolite, and locally in granulite, facies during waning tectonic activity, and most rocks have equigranular mosaic textures. Although it is extensively recrystallised and deformed, the Fiskenæsset Complex locally preserves a variety of little deformed igneous structures and cumulate textures which demonstrate the important influence of both gravitational and current action during igneous crystallisation. Various kinds of igneous layering provide primary way-up structures which can be used to interpret the facing directions of Fl folds, and various stages of deformation of cumulate textures provide evidence of the tectonic and metamorphic processes by which banded anorthositic gneisses and amphibolites were derived from igneous rocks by progressive deformation.

Proterozoic paleocurrents and depositional history of the East Arm fold belt, Great Slave Lake, Northwest Territories

1969 ◽  
Vol 6 (3) ◽  
pp. 441-462 ◽  
Author(s):  
Paul Hoffman
Keyword(s):  
Volcanic Rocks ◽  
Canadian Shield ◽  
Stratigraphic Correlation ◽  
Fold Belt ◽  
Axial Zone ◽  
Depositional History ◽  
Great Slave Lake ◽  
History Of ◽  
Three Stages ◽  
Fault Scarps

Nearly 40 000 ft (~12 190 m) of unmetamorphosed Aphebian (and possibly lowermost Helikian) sedimentary and volcanic rocks are exposed in the East Arm of Great Slave Lake. This sequence is an erosional remnant of an Appalachian-type geosynclinal complex with a NNW depositional strike. Integrated paleocurrent, stratigraphic, and sedimentological analysis reveals three stages in the depositional history of the complex: (1) a double transgressive, pre-orogenic miogeosyncline, which received sediment from a distant cratonic source to the ENE and which becomes thicker and more eugeosynclinal to the WSW; (2) a regressive, syn-orogenic exogeosyncline (clastic wedge), which received sediment from rapidly uplifted tectonic lands to the WSW; and (3) a continental, post-orogenic taphrogeosyncline (down-faulted intermontaine trough), which received sediment locally from block-fault scarps within the East Arm area.Facies predictions based on this model provide criteria for establishing stratigraphic correlation and contiguity between the East Arm and other Aphebian sequences in the northwestern Canadian Shield. The prevailing depositional strike is roughly perpendicular to the tectonic strike of the East Arm Fold Belt, and it should not therefore be assumed that depositional strike parallels tectonic strike in other belts. The Bear Province may have been the site of the orogenically active axial zone of the geosyncline, but that part of the Churchill Province near the East Arm remained passive until the final post-orogenic stage of sedimentation and may therefore be of epeirogenic origin.

scholarly journals Isotopic age determinations from South Greenland and their geological setting

1965 ◽  
Vol 53 ◽  
pp. 1-56
Author(s):  
D Bridgwater
Keyword(s):  
Biotite Granite ◽  
Canadian Shield ◽  
Granitic Rocks ◽  
Isotopic Age ◽  
Fold Belt ◽  
South West ◽  
Intrusive Rocks ◽  
Igneous Activity ◽  
Fold Belts ◽  
Age Determinations

A brief geological review of the area between Sermiligârssuk and Kap Farvel is given using the following five main divisions of the Precambrian of South Greenland: 1) pre-Ketilidian (? 2000-2700 m. y.) 2) Ketilidian (? 1700-2000 m. y.) 3) post-Ketilidian = Kuanitic (? 1650-1700 m. y.) 4) Sanerutian (? 1500-1650 m. y.) 5) Gardar (1020-?1500 m.y.). In the area described these divisions are characterized by: 1) gneisses, 2) geosynclinal sedimentation and lava extrusion, metamorphism and plutonism, 3) basic and intermediate dyking, 4) renewed plutonism, and emplacement of synplutonic basic, intermediate and granitic rocks, 5) post-orogenic sedimentation, lava extrusion and a predominantly alkali suite of intrusive rocks. Isotopic age determinations are available from the two youngest of the above divisions in South Greenland; dates for the three older divisions are suggested by comparison of the development of South Greenland with other fold belts together with sparse data from elsewhere in Greenland. It is suggested that the pre-Ketilidian gneisses represent the remnant of an old fold belt formed approximately 2400-2700 m. y. ago which has been reactivated during the Ketilidian and Sanerutian plutonic episodes in South Greenland. It is further suggested that the Ketilidian, post-Ketilidian and Sanerutian episodes are phases in the evolution of one fold belt which started at approximately 2000 m. y. ago and represents the beginning of the Svecofennid chelogenic cycle in South Greenland. The Gardar magmatism is regarded as a typical post-orogenic alkali suite and it is thought that the Gardar activity at about 1200 m. y. may represent compensatory tensional conditions on the margins of the developing Grenville fold belt which probably passed south of Greenland. Eight K/Ar age determinations (Geochron Laboratories) give the following results: Sanerutian hypersthene gabbro, 1645 m. y. (biotite) and 1700 m. y. (augite); Sanerutian granite, 1620 m. y. (biotite) ; early Gardar dolerite, 1435 m. y. (augite); Gardar syenite, 1128 m. y. (biotite) and 1355 m. y. (augite); inclusion of anorthosite fragment in a Gardar dyke, 1025 m. y. (biotite) and 1075 m. y. (augite). Four Rb/Sr age determinations (Moorbath) give the following results: Ketilidian pegmatite affected by Sanerutian metamorphism, 1630 m. y; Sanerutian granite, 1615 m. y.; Sanerutian granite probably affected by Gardar event, 1220 m. y.; Gardar biotite granite, 1150 m. y. Results from other areas in Greenland are discussed and it is suggested that a large part of the south-west coastal strip is pre-Ketilidian in age and that the Nagssugtoqidian fold belt was formed at approximately the same time as the Ketilidian-Sanerutian fold belt in South Greenland, that is at the beginning of the Svecofennid chelogenic cycle. It is suggested that the main episodes described from South Greenland correspond to events in the Canadian shield as follows: pre-Ketilidian plutonism = Kenoran; Ketilidian-Sanerutian and Nagssugtoqidian = Hudsonian; Gardar = post-Hudsonian, pre-Grenville igneous activity. Tectono-igneous cycles are used in conjunction with basic dykes and age determinations as a method of dividing the Precambrian.

Mechanism of phenocryst formation in alkaline ultrabasic and basic volcanic rocks: Evidence from Makhtesh Ramon, southern Israel

2005 ◽  
Vol 54 (2) ◽  
pp. 113-120 ◽  
Author(s):  
Eli Shimshilashvili ◽  
Zinovy Yudalevich
Keyword(s):  
Volcanic Rocks ◽  
Basic Volcanic

The mid-Paleozoic deformation in the Hazen fold belt, Ellesmere Island, Arctic Canada

1990 ◽  
Vol 27 (10) ◽  
pp. 1359-1370 ◽  
Author(s):  
Eva M. Klaper
Keyword(s):  
Large Scale ◽  
Ellesmere Island ◽  
Small Scale ◽  
Northwestern Part ◽  
Fold Belt ◽  
Southeastern Part ◽  
Lower Paleozoic ◽  
Slip Mechanism ◽  
Fold Belts ◽  
Surface Geology

The mid-Paleozoic deformation of lower Paleozoic subgreenschist-facies sediments of the Hazen fold belt in northern Ellesmere Island is represented predominantly by chevron-style folding. Folded multilayers display cleavage fans suggesting synchronous fold and cleavage formation. Bedding-parallel slip indicates a flexural slip mechanism of folding. The geometry of several large-scale anticlinoria has been interpreted as being due to formation of these structures over detachments and thrust ramps.The constant fold geometry, the parallel orientation of faults and large- and small-scale folds, and the axial-plane foliation are related to a single phase of folding with a migrating deformation front in the Hazen fold belt during the mid-Paleozoic orogeny. The minimum amount of shortening in the Hazen and Central Ellesmere fold belts has been estimated from surface geology to increase from 40–50% of the original bed length in the external southeastern part to 50–60% in the more internal northwestern part of the belts.The convergent, thin-skinned nature of the Hazen and Central Ellesmere fold belts indicates that the postulated transpressive plate motions during the accretion of Pearya did not affect the study area.

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