Geochemistry, mineral chemistry and petrogenesis of a Neoproterozoic dyke swarm in the north Eastern Desert, Egypt

2006 ◽  
Vol 143 (1) ◽  
pp. 115-135 ◽  
Author(s):  
M. DAWOUD ◽  
H. A. ELIWA ◽  
G. TRAVERSA ◽  
M. S. ATTIA ◽  
T. ITAYA
Keyword(s):  
Tectonic Setting ◽  
Mineral Chemistry ◽  
Eastern Desert ◽  
Major And Trace Elements ◽  
Dyke Swarm ◽  
Mafic Dyke ◽  
Crustal Rocks ◽  
The North ◽  
Chemical Signatures ◽  
Dyke Swarms

Dyke swarms traverse Neoproterozoic rocks in the Hawashiya region in the extreme northern part of the Eastern Desert of Egypt. They are a suite of basaltic andesite and andesite mafic dykes, and dacitic and rhyolitic felsic dykes. The mafic dyke suite is more abundant in the younger granites (577 ± 6 Ma) than in the older granitoids (614 Ma), in which the felsic dykes are the most common. The dyke swarms trend predominantly NE–SW, and the felsic dyke suite is older than the mafic dyke suite. Both dyke suites are calc-alkaline (alkaline dykes are rare) and are relatively poor in TiO2 and Nb but enriched in the incompatible elements and HFSE. The felsic dyke suite is enriched in REE and is strongly LREE fractionated relative to the mafic dyke suite. Although the Hawashiya dykes were emplaced at the end of the Neoproterozoic era in an extensional tectonic setting, they have geochemical characteristics that are consistent with a subduction-related regime. These chemical signatures were inherited from the lithospheric rocks that produced their host Hawashiya granitoids. The felsic dyke suite magma may be derived from crustal rocks (essential source component) by partial melting. The mafic dyke suite magma was generated from a lithospheric mantle and has undergone fractional crystallization of plagioclase, amphibole, clinopyroxene and magnetite, as documented by major and trace elements fractionation modelling.

The Silurian(?) Passamaquoddy Bay mafic dyke swarm, New Brunswick: petrogenesis and tectonic implications

2001 ◽  
Vol 38 (11) ◽  
pp. 1565-1578 ◽  
Author(s):  
Nancy A Van Wagoner ◽  
Matthew I Leybourne ◽  
Kelsie A Dadd ◽  
Miranda LA Huskins
Keyword(s):  
New Brunswick ◽  
Incompatible Element ◽  
Tectonic Setting ◽  
Crustal Contamination ◽  
Dyke Swarm ◽  
Mafic Dyke ◽  
Mafic Dykes ◽  
The North ◽  
Passamaquoddy Bay ◽  
Mafic Dyke Swarm

The volcanic and sedimentary rocks of the Passamaquoddy Bay (PB) area of southeastern New Brunswick are part of the Silurian–Devonian Coastal Volcanic Belt (CVB), an extensive belt of bimodal volcanic rocks. The PB sequence is 4 km thick, has four cycles of mafic and felsic volcanism, and is intruded by mafic dykes at all levels. There are two ages of dykes, those related to the Late Silurian PB volcanism (PB dykes) and Mesozoic dykes (the Minister Island Dyke) related to the opening of the North Atlantic. The PB mafic dykes are subalkalic basalt to basaltic andesite, within-plate tholeiites. The dykes are moderately to highly evolved (Mg# = 66.6 to 26.6), with trends of major and trace elements typical of the fractionation of olivine, pyroxene, plagioclase, and ilmenite. The PB mafic dyke swarm comprises over 155 dykes which represent a greater range of compositions than the associated flows, suggesting that they give a more complete representation of the Late Silurian PB mafic magmas. They exhibit incompatible element characteristics best accounted for by crustal contamination. The dykes plot on a linear array away from mantle mixing lines between depleted and enriched mantle sources and toward the composition of the PB felsic units, suggesting that these felsic units are representative of partial melts and fractionates of the source contaminate. The variable TiO2 contents (1.2–4.3 wt.%) and incompatible element ratio trends plotted against a fractionation index suggest that mantle metasomatism, either fluid or melt derived, may also have influenced the mantle source of the dykes. The dykes dip steeply and have a relatively consistent strike to the north. Most dykes range in thickness from 0.5 to 2 m, but range up to 9 m. The single orientation of the dykes, along with their chemical characteristics and volume, and association with a bimodal intraplate volcanic sequence, are consistent with an extensional tectonic setting. Constraints of the regional geology suggest that this extension was associated with convergence, perhaps in a back-arc setting.

U–Pb geochronology and geochemical variation within two Proterozoic mafic dyke swarms, Labrador

1993 ◽  
Vol 30 (7) ◽  
pp. 1490-1504 ◽  
Author(s):  
Andrew C. Cadman ◽  
Larry Heaman ◽  
John Tarney ◽  
Richard Wardle ◽  
Thomas E. Krogh
Keyword(s):  
North Atlantic ◽  
Major Element ◽  
Dyke Swarm ◽  
Mafic Dyke ◽  
Element Abundances ◽  
Long Period ◽  
The North ◽  
Geochemical Variation ◽  
Dyke Swarms ◽  
North Atlantic Craton

An Early Proterozoic Kikkertavak mafic dyke intruding the Archaean Hopedale block, Labrador, gives an age of 2235 ± 2 Ma using U–Pb techniques on baddeleyite. A Harp mafic dyke in the same area gives an age of 1273 ± 1 Ma using U–Pb techniques on baddeleyite and zircon. The latter age is almost identical to that of the giant Mackenzie swarm and to the age of the BD0 dykes in South Greenland, and points to a major pulse of mafic magmatism over much of the North Atlantic craton at this time. The former age is a little older than available Rb–Sr ages for the extensive MD swarm in West Greenland, but there are possible correlatives.Geochemical data are presented to ascertain whether there are significant compositional differences between the Harp and Kikkertavak dyke swarms. In fact, two distinct chemical subgroups can be recognized within the Kikkertavak dykes, and three others are recognized within the Harp suite. These differences apply more to trace element patterns rather than major element abundances, but although there are compositional differences between the average Harp and average Kikkertavak dyke, it is unlikely that geochemistry could be used unequivocally to separate the two. The compositional differences probably reflect evolutionary processes in the lithosphere. The range of composition exemplified by the subgroups is most easily interpreted in terms of proportion of asthenosphere and lithosphere components, and does not necessarily imply that either dyke swarm was emplaced over a long period. The presence of subgroups within both swarms urges some caution in assuming all dykes correspond to one or other age.

Whole-rock and mineral chemistry of cumulates from the Kızıldağ (Hatay) ophiolite (Turkey): clues for multiple magma generation during crustal accretion in the southern Neotethyan ocean

2005 ◽  
Vol 69 (1) ◽  
pp. 53-76 ◽  
Author(s):  
U. Bağci ◽  
O. Parlak ◽  
V. Höck
Keyword(s):  
Tectonic Setting ◽  
Mineral Chemistry ◽  
Chromian Spinel ◽  
Olivine Gabbro ◽  
Crustal Accretion ◽  
Magma Generation ◽  
The North ◽  
Rock Types ◽  
Suprasubduction Zone ◽  
Ocean Ridge

AbstractThe late Cretaceous Kızıldağ ophiolite forms one of the best exposures of oceanic lithospheric remnants of southern Neotethys to the north of the Arabian promontory in Turkey. The ultramafic to mafic cumulate rocks, displaying variable thickness (ranging from 165 to 700 m), are ductiley deformed, possibly in response to syn-magmatic extension during sea-floor spreading and characterized by wehrlite, olivine gabbro, olivine gabbronorite and gabbro. The gabbroic cumulates have an intrusive contact with the wehrlitic cumulates in some places. The crystallization order of the cumulus and intercumulus phases is olivine (Fo86–77)± chromian spinel, clinopyroxene (Mg#92–76), plagio-clase(An95–83), orthopyroxene(Mg#87–79). The olivine, clinopyroxene, orthopyroxene and plagioclase in ultramafic and mafic cumulate rocks seem to have similar compositional range. This suggests that these rocks cannot represent a simple crystal line of descent. Instead the overlapping ranges in mineral compositions in different rock types suggest multiple magma generation during crustal accretion for the Kızıldağ ophiolite. The presence of high Mg# of olivine, clinopyroxene, orthopyroxene, and the absence of Ca-rich plagioclase as an early fractionating phase co-precipitating with forsteritic olivine, suggest that the Kızıldağ plutonic suite is not likely to have originated in a mid-ocean ridge environment. Instead the whole-rock and mineral chemistry of the cumulates indicates their derivation from an island arc tholeiitic (IAT) magma. All the evidence indicates that the Kızıldağ ophiolite formed along a slow-spreading centre in a fore-arc region of a suprasubduction zone tectonic setting.

The 2405 Ma and 2310 Ma Mafic Dyke Swarms in the Karelian Craton: Age, Chemical and Sr-Nd Isotope Composition, and Tectonic Setting

2016 ◽  
Vol 90 (s1) ◽  
pp. 123-123
Author(s):  
A.V. Stepanova ◽  
E.B. Salnikova ◽  
A.V. Samsonov ◽  
Yu.O. Larionova ◽  
S.V. Egorova ◽  
...  
Keyword(s):  
Isotope Composition ◽  
Tectonic Setting ◽  
Mafic Dyke ◽  
Karelian Craton ◽  
Nd Isotope ◽  
Dyke Swarms ◽  
Nd Isotope Composition

Paleomagnetism and U-Pb geochronology of diabase dyke swarms of Minto block, Superior Province, Quebec, Canada

1998 ◽  
Vol 35 (9) ◽  
pp. 1054-1069 ◽  
Author(s):  
Kenneth L Buchan ◽  
James K Mortensen ◽  
Kenneth D Card ◽  
John A Percival
Keyword(s):  
Collaborative Study ◽  
Sedimentary Rocks ◽  
Dyke Swarm ◽  
Superior Province ◽  
Mafic Dyke ◽  
Magnetization Direction ◽  
Virtual Geomagnetic Pole ◽  
Southern Province ◽  
Geomagnetic Pole ◽  
Dyke Swarms

In the first collaborative study of paleomagnetism and precise U-Pb geochronology in the Minto block of the Superior Province, mafic dyke swarms with three widely divergent paleomagnetic signatures and isotopic ages have been identified. The 2505 ± 2 Ma Ptarmigan dykes trend north to northeast and have a virtual geomagnetic pole at 42°S, 220°E, similar to that of 2473-2446 Ma Matachewan dykes of the southern Superior Province. The ca. 2230 Ma Maguire dykes trend west to northwest and yield a paleopole at 9°S, 267°E, similar to those for 2216+8-4 Ma Senneterre dykes and 2217-2210 Ma Nipissing sills of the southern Superior and Southern provinces, respectively. The 2209 ± 1 Ma Klotz dykes trend west-northwest, but do not carry a consistent magnetization direction. Finally, 1998 ± 2 Ma Minto dykes of west-northwest to northwest trend, identical in age to the 1998 Ma ± 2 Ma Purtuniq ophiolite of the Cape Smith Belt, have a paleopole at 38°N, 174°E. The similarity of paleopoles for the ca. 2.23-2.21 Ga Maguire dykes of the Minto block, Senneterre dykes of the southern Superior, and Nipissing sills of the Southern Province demonstrates that these regions were in their present relative latitudes and orientations at that time. Likewise, the similarity of the Ptarmigan virtual geomagnetic pole and the Matachewan paleopole suggests little relative latitudinal movement or rotation of the two regions since ca. 2.5 Ga. The Maguire, Senneterre, and Klotz dykes form a roughly radiating pattern and may represent one quadrant of a giant radiating dyke swarm centred southeast of Ungava Bay, whose focus marks the location of a mantle plume responsible for ca. 2.22 Ga breakup along the eastern margin of the Superior Province. If so, the coeval Nipissing sills that intrude sedimentary rocks of the Huronian Supergroup of the Southern Province may have been fed laterally by Senneterre dykes from the Ungava plume centre.

Zircon U–Pb ages, major and trace elements, and Hf isotope characteristics of the Tiantangzhai granites in the North Dabie orogen, Central China: tectonic implications

2013 ◽  
Vol 151 (5) ◽  
pp. 916-937 ◽  
Author(s):  
XIN DENG ◽  
KUNGUANG YANG ◽  
ALI POLAT ◽  
TIMOTHY M. KUSKY ◽  
KAIBIN WU
Keyword(s):  
Partial Melting ◽  
Eastern China ◽  
Major And Trace Elements ◽  
Central China ◽  
Dabie Orogen ◽  
Crustal Rocks ◽  
The North ◽  
Granitic Magmatism ◽  
Two Peaks ◽  
Lower Crustal

AbstractCretaceous granites are widespread in the North Dabie orogen, Central China, but their emplacement sequence and mechanism are poorly known. The Tiantangzhai Complex in the North Dabie Complex is the largest Cretaceous granitic suite consisting of six individual intrusions. In this study, zircon U–Pb ages are used to constrain the crystallization and protolith ages of these intrusions. The Shigujian granite is a syn-tectonic intrusion with an age of 141 Ma. This granite was emplaced under a compressional regime. Oscillatory rims of zircons have yielded two peaks at 137±1 Ma and 125±1 Ma. The 137±1 Ma peak represents the beginning of orogenic extension and tectonic collapse, whereas the 125±1 Ma peak represents widespread granitic magmatism. Zircon cores have yielded concordant ages between 812 and 804 Ma, which indicate a crystallization age for the protolith. The Tiantangzhai granites show relatively high Sr contents and high La/Yb and Sr/Y ratios. The Shigujian granite has positive Eu anomalies resulting from partial melting of a plagioclase-rich source in an over-thickened crust. Correspondingly, in situ Lu–Hf analyses from zircons yield high negative εHf(t) values from −24.8 to −26.6, with two-stage Hf model ages from 2748±34 to 2864±40 Ma, suggesting that the magmas were dominantly derived from partial melting of middle to lower crustal rocks. The Dabie orogen underwent pervasive NW–SE extension at the beginning of the early Cretaceous associated with subduction of the Palaeo-Pacific plate beneath eastern China.

Pb, Nd, Sr isotopic composition of the Mesoproterozoic mafic intrusions (Udzha paleorift, Northern Siberia)

2020 ◽  
Author(s):  
Lidiia Shpakovich ◽  
Sergey Malyshev ◽  
Valeriy Savatenkov
Keyword(s):  
Isotopic Composition ◽  
Siberian Craton ◽  
Dyke Swarm ◽  
Mafic Dyke ◽  
Russian Science ◽  
Mafic Intrusions ◽  
Anabar Shield ◽  
History Of ◽  
Pb Isotopic Composition ◽  
Dyke Swarms

<p>Geodynamic reconstructions are largely based on information contained in mafic igneous rocks, including dykes and sills. The age and isotope-geochemical characteristics of such rocks are inevitable for understanding of geodynamic history of the Proterozoic cratons. The regions in Siberian Craton, where Precambrian mafic dyke swarms are known are following: Anabar Shield and Olenek Uplifts, Aldan-Stanovoi Shield, SE area of Siberian Craton, and smaller Uplifts on the SW margin of Siberian Craton.</p><p>The Udzha paleo-rift is located in the northern part of Siberian Craton between Anabar and Olenek Uplifts is also associated with mafic dyke swarm. These dykes cross-cut the pre-Neoproterozoic sedimentary successions. The age of the largest dyke in Udzha paleo-rift (Great Udzha Dyke) presented by medium-grained dolerite was determined to be 1386 ± 30 Ma (Malyshev et al., 2018).</p><p>We present new data of Sr, Nd and Pb isotopic composition on the Udzha paleo-rift dykes, determined by TIMS. The initial isotopic composition of Pb in the dykes was obtained using the leaching method by Savatenkov et al., 2019. The Sr isotopic composition of the dykes demonstrates substantial variation (εSr varies from 8.4 to 110.4). We do not consider this fact as a result of crust contamination, because Nd isotopic composition does not vary significantly (εNd varies from -1.4 to 0.7). Obtained results indicate that initial for the Udzha paleo-rift dykes melts were generated from two mantle reservoirs of DM and EMII-type. The initial Pb isotopic composition of the dykes reveals EMII source participation in the melts generation too (<sup>206</sup>Pb/<sup>204</sup>Pb varies from 16.133 to 16.266, <sup>207</sup>Pb/<sup>204</sup>Pb varies from 15.343 to 15.458). The presence of enriched component is likely associated with lithospheric mantle, metasomatized by fluids, derived from subducted terrigenous material.</p><p>The studies were supported by the Russian Science Foundation project No. 19-77-10048.</p><p>References</p><p>Malyshev, S. V., Pasenko A. M., Ivanov A. V., Gladkochub D. P., Savatenkov V. M., Meffre S., Abersteiner A., Kamenetsky V. S. & Shcherbakov V. D. (2018): Geodynamic Significance of the Mesoproterozoic Magmatism of the Udzha Paleo-Rift (Northern Siberian Craton) Based on U-Pb Geochronology and Paleomagnetic Data. – Minerals, 8(12), 555</p><p>Savatenkov V. M., Malyshev, S. V., Ivanov A. V., Meffre S., Abersteiner A., Kamenetsky V. S., Pasenko A. M. (2019): An advanced stepwise leaching technique for derivation of initial lead isotope ratios in ancient mafic rocks: A case study of Mesoproterozoic intrusions from the Udzha paleo-rift, Siberian Craton. – Chemical Geology, 528, 119253</p>

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