Moine─Dalradian relationships and their palaeotectonic significance

1984 ◽  
Vol 395 (1809) ◽  
pp. 185-202 ◽  
Keyword(s):  
Thick Layer ◽  
High Heat ◽  
Source Rocks ◽  
Mineral Deposits ◽  
Common Source ◽  
Calc Alkaline ◽  
Isotopic Data ◽  
Moine Rocks ◽  
Southeastern Margin ◽  
Southern Highland

Regional geochemical and lithogeochemical data, when reviewed in relation to the development of the Caledonian orogen in Scotland, indicate that the Moine-Dalradian boundary coincides with a long-lived crustal discontinuity. It is suggested that this boundary follows the original southeastern margin of an old continental slab in which the Lewisian basement was overlain by a thick layer of ‘Old Moine’ metasediments affected by pre-Caledonian (750 Ma or over) deformation and metamorphism. Early Caledonian ‘Young Moine’ sediments on this slab resemble the underlying metasediments in lithofacies but are somewhat poorer in Zr and Y. To the southeast of the boundary, a thick Dalradian succession accumulated in a marine ensialic basin on a thinned basement of granulites and gneisses. In the Dalradian, elements of basic-ultrabasic association are high, especially in the upper Argyll and Southern Highland Groups where they are associated with products of basic volcanicity. Stratabound Ba, Pb and Zn mineral deposits occur widely not far below the volcanic horizon, and magmatism and mineralization are attributed to the opening of a palaeo-oceanic rift within the Dalradian basin. The geochemistry of the Torridonian, Old Moine and Young Moine detrital sediments suggests derivation from a common source dominated by intermediate-acid calc-alkaline rocks. Low to moderate large-ion litho-phile (l. i. l.) element levels suggest variable degrees of depletion caused by deep metamorphism of the source rocks. Isotopic data show that the sourceland was Archaean and early Proterozoic, and suggest that it may have resembled the Ketilidian and pre-Ketilidian of southern Greenland. The geochemical influence of this ancient western sourceland can be recognized throughout the Dalradian succession, constraining models that involve the availability of young island arc or exotic tectonic materials during the filling of the Dalradian basin. The mechanical strength, relatively low density and high heat production of the Old Moine rocks enhanced the contrast between the crustal slab incorporating a thick Moine layer and the main Dalradian basin beneath which this layer is absent. Tectonic and metamorphic develop­ments differed in the adjacent regions during orogeny, and deep discon­tinuities at the Moine-Dalradian boundary acted as conduits for Late Caledonian appinitic and metalliferous granites rising from sub-crustal sources.

scholarly journals Geochemical Classification and Geotectonic Setting of Granitic Gneisses from Southeastern Margin of Western Nigeria Basement

2021 ◽  
Vol 3 (2) ◽  
Author(s):  
Mohammed Olatoye Adepoju ◽  
Yinusa Ayodele Asiwaju-Bello
Keyword(s):  
Inductively Coupled Plasma ◽  
Tectonic Setting ◽  
Calc Alkaline ◽  
Granitic Gneiss ◽  
Basement Complex ◽  
Southwestern Nigeria ◽  
Inductively Coupled ◽  
Continental Arc ◽  
Southeastern Margin ◽  
Geochemical Classification

Chemical whole-rock major oxides and some trace element analyses were done on granitic gneiss rocks located on the southeastern margin of western Nigeria Basement Complex, exposed in parts of Dagbala-Atte District, southwestern Nigeria. This was meant to classify the rocks and to understand the tectonic setting in order to evaluate their crustal evolution. The chemical analyses were done using inductively-coupled plasma mass spectrometer. From the results obtained, these rocks classified into calc-alkaline to shoshonite series with metaluminous to peraluminous varieties, they are I-type granitoids of feroan composition. The granitic gneisses formed from metamorphism of granite and granodiorite. Tectonically, most of the rock samples plotted in the field of island arc, continental arc and continental-collisional granitoids, which indicated that the protolith granite and granodiorite are orogenic and are arc related inferring arc tectonic setting.

scholarly journals 207Pb-206Pb dating of magnetite, monazite and allanite in the central and northern Nagssugtoqidian orogen, West Greenland

2006 ◽  
Vol 11 ◽  
pp. 101-114 ◽  
Author(s):  
Henrik Stendal ◽  
Karsten Secher ◽  
Robert Frei
Keyword(s):  
Hydrothermal Activity ◽  
Alkaline Magmatism ◽  
Calc Alkaline ◽  
Isotopic Data ◽  
Sulphide Deposit ◽  
Late Archaean ◽  
West Greenland ◽  
Isotopic Signatures ◽  
Source Characteristics ◽  
Isotopic Measurements

Pb-isotopic data for magnetite from amphibolites in the Nagssugtoqidian orogen, central West Greenland, have been used to trace their source characteristics and the timing of metamorphism. Analyses of the magnetite define a Pb-Pb isochron age of 1726 ± 7 Ma. The magnetite is metamorphic in origin, and the 1726 Ma age is interpreted as a cooling age through the closing temperature of magnetite at ~600°C. Some of the amphibolites in this study come from the Naternaq supracrustal rocks in the northern Nagssugtoqidian orogen, which host the Naternaq sulphide deposit and may be part of the Nordre Strømfjord supracrustal suite, which was deposited at around 1950 Ma ago. Pb-isotopic signatures of magnetite from the Arfersiorfik quartz diorite in the central Nagssugtoqidian orogen are compatible with published whole-rock Pb-isotopic data from this suite; previous work has shown that it is a product of subduction-related calc-alkaline magmatism between 1920 and 1870 Ma. Intrusion of pegmatites occurred at around 1800 Ma in both the central and the northern parts of the orogen. Pegmatite ages have been determined by Pb stepwise leaching analyses of allanite and monazite, and source characteristics of Pb point to an origin of the pegmatites by melting of the surrounding late Archaean and Palaeoproterozoic country rocks. Hydrothermal activity took place after pegmatite emplacement and continued below the closure temperature of magnetite at 1800– 1650 Ma. Because of the relatively inert and refractory nature of magnetite, Pb-isotopic measurements from this mineral may be of help to understand the metamorphic evolution of geologically complex terrains.

Cenozoic high Sr/Y volcanic rocks in the Qiangtang terrane, northern Tibet: geochemical and isotopic evidence for the origin of delaminated lower continental melts

2008 ◽  
Vol 145 (4) ◽  
pp. 463-474 ◽  
Author(s):  
SHEN LIU ◽  
RUI-ZHONG HU ◽  
CAI-XIA FENG ◽  
HAI-BO ZOU ◽  
CAI LI ◽  
...  
Keyword(s):  
Subduction Zones ◽  
Volcanic Rocks ◽  
Mantle Peridotite ◽  
Calc Alkaline ◽  
Isotopic Data ◽  
Slab Melting ◽  
Northern Tibet ◽  
High K ◽  
T Values ◽  
Qiangtang Terrane

AbstractGeochemical and Sr–Nd–Pb isotopic data are presented for volcanic rocks from Zougouyouchaco (30.5 Ma) and Dogai Coring (39.7 Ma) of the southern and middle Qiangtang block in northern Tibet. The volcanic rocks are high-K calc-alkaline trachyandesites and dacites, with SiO2 contents ranging from 58.5 to 67.1 wt % The rocks are enriched in light REE (LREE) and contain high Sr (649 to 986 ppm) and relatively low Yb (0.8 to 1.2 ppm) and Y (9.5 to 16.6 ppm) contents, resulting in high La/Yb (29–58) and Sr/Y (43–92) ratios, as well as relatively high MgO contents and Mg no., similar to the compositions of adakites formed by slab melting in subduction zones. However, the adakitic rocks in the Qiangtang block are characterized by relatively low εNd(t) values (−3.8 to −5.0) and highly radiogenic Sr ((87Sr/86Sr)i=0.706–0.708), which are inconsistent with an origin by slab melting. The geochemistry and tectonics indicate that the adakitic volcanic rocks were most likely derived from partial melting of delaminated lower continental crust. As the pristine adakitic melts rose, they interacted with the surrounding mantle peridotite, elevating their MgO values and Mg numbers.

Geochemistry and isotopic evolution of the Mesoproterozoic Cape Meredith Complex, West Falkland

2000 ◽  
Vol 137 (5) ◽  
pp. 537-553 ◽  
Author(s):  
ROBERT J. THOMAS ◽  
JOACHIM JACOBS ◽  
BRUCE M. EGLINGTON
Keyword(s):  
High Field ◽  
Alkaline Basalt ◽  
Thin Sheets ◽  
Calc Alkaline ◽  
Isotopic Data ◽  
High Field Strength ◽  
Geological Evolution ◽  
Isotopic Evolution ◽  
Dronning Maud Land ◽  
Granitoid Gneisses

Whole-rock major and trace element geochemical and Rb–Sr/Sm–Nd isotopic data are presented for the Mesoproterozoic (∼1.0 Ga) metamorphic and igneous rocks of the Cape Meredith Complex, West Falkland. The data indicate that the oldest rocks, the ∼1.1 Ga supracrustal gneisses of the Big Cape Formation, which form three petrographic and geochemical groups (mafic amphibolite, quartz–plagioclase–biotite–hornblende intermediate gneiss and acid gneiss), probably represent a juvenile calc-alkaline, basalt–andesite–rhyolite volcanic sequence, with epsilon (εNdT) values and NdTDM ages of ∼+3 to +6 and ∼1100 to 1400 Ma respectively. It is argued on geochemical grounds that these metavolcanics were extruded in an island-arc at around 1120 Ma. The Big Cape Formation was intruded by granitoids during and after a collisional orogenic event at around 1090 Ma. The oldest, foliated, (G1) granodiorite was emplaced as thin sheets at approximately 1090 to 1070 Ma and is characterized by εNd values of ∼+1.5 to 4 (TDM = ∼1200 to 1400 Ma), showing its juvenile nature. The ∼1070 Ma (G2) syntectonic granitoid gneisses and ∼1000 Ma G3 post-tectonic granites also exhibit juvenile characteristics (εNd = ∼0 to +5 and TDM = 2200 to 1200 Ma, respectively). The granitoids show a time-composition evolution from Na-rich (G1) granodiorite to potassic, high-High Field Strength Element granites (G3). The geochemical and isotopic characteristics and geological evolution of the Cape Meredith Complex is comparable with that of the adjacent Gondwana crustal blocks in Natal (SE Africa) and Dronning Maud Land (East Antarctica), supporting models that demonstrate these areas evolved in a contiguous, juvenile arc environment prior to, and during, a major orogenic event at ∼1.1 Ga. These events were associated with the birth of the Rodinian supercontinent. The three areas remained juxtaposed during Rodinia break-up and were subsequently incorporated into Gondwana in the same relative positions.

A Discussion on the evolution of the Precambrian crust - The early Precambrian gneisses of the Godthåb district, West Greenland

1973 ◽  
Vol 273 (1235) ◽  
pp. 343-358 ◽  
Keyword(s):  
Amphibolite Facies ◽  
Calc Alkaline ◽  
Isotopic Data ◽  
Early Precambrian ◽  
West Greenland ◽  
Metasedimentary Rocks ◽  
Parent Rocks

Intensely metamorphosed and deformed basic dykes, the Ameralik dykes, have been used to divide the amphibolite-facies gneisses of the Godthåb district into the Amitsoq gneisses (older) and the Nuk gneisses. Metavolcanic and metasedimentary rocks (the Malene supracrustals), and stratiform meta-anorthosites are also present and are probably younger than the Amitsoq gneisses, but are older than the Nuk gneisses. The Amitsoq gneisses contain abundant fragments of Ameralik dykes. They appear to have been derived from homogeneous granitic (s.l.) parents, but most of them have been intensely reworked before and/or after the intrusion of the Ameralik dykes and are now banded gneisses. They range from dioritic to granitic in composition and potassic varieties are common. Isotopic data indicate that the parent rocks of the gneisses were emplaced or metamorphosed about 3750 Ma ago. Ameralik dykes are absent from the Nuk gneisses, which are the most abundant rocks in the area. These gneisses are derived from intrusive calc-alkaline parents, mainly tonalites and granodiorites, and represent a massive addition of granitic material to this level of the crust about 3080 Ma ago, after the first supracrustal rocks had been laid down.

scholarly journals Rhyacian evolution of the eastern São Luís Craton: petrography, geochemistry and geochronology of the Rosário Suite

2017 ◽  
Vol 47 (2) ◽  
pp. 275-299 ◽  
Author(s):  
Bruna Karine Correa Nogueira ◽  
Paulo Sergio de Sousa Gorayeb ◽  
Elton Luiz Dantas ◽  
Rafael Estumano Leal ◽  
Marco Antonio Galarza
Keyword(s):  
Shear Zones ◽  
Crustal Evolution ◽  
Calc Alkaline ◽  
Isotopic Data ◽  
Crust Formation ◽  
Magmatic Arc ◽  
Continental Arc ◽  
Amazonian Craton ◽  
Granitoid Rocks ◽  
Geochemical Studies

ABSTRACT: The São Luís Cráton comprises an area between northeast Pará state and northwest Maranhão that exposes Paleoproterozoic granitic suites and meta-volcanosedimentary sequences. In the east of this geotectonic unit, about 70 km south of São Luís, there is a portion of the São Luís Craton, represented by the intrusive Rosario Suite (RS). This work is focused on rocks of this suite, including petrographic, lithochemical and geochronological studies to understand the crustal evolution of these granitoid rocks. The rock spectrum varies from tonalitic to granodioritic, quartz dioritic and granitic compositions, and there are partial structural and mineralogical changes related to deformation along transcurrent shear zones. The geochemical studies show granitic metaluminous compositions of the calc-alkaline series with I-type affinity typical of magmatic arc. Rare earth elements show marked fractionation and slight Eu positive or negative anomalies (Eu/Eu* = 0.82 to 1.1). Zircon U-Pb data provided consistent ages of 2165 ± 7 Ma, 2170 ± 7 Ma, 2170 ± 7 Ma, 2161 ± 4 Ma and 2175 ± 8 Ma, dating emplacement of these granitoids as Paleoproterozoic (Rhyacian). Sm-Nd isotopic data provided model ages (TDM) of 2.21 to 2.31 Ga with positive values of εNd +1.9 to +3.2 (t = 2.17 Ga), indicating predominantly Rhyacian crustal sources for the parental magmas, similar to those ones found in other areas of the São Luís Craton. The data, integrated with published geological and geochronological information, indicate the occurrence of an important continental crust formation event in this area. The Paleoproterozoic evolution between 2.17 and 2.15 Ga is related to the Transamazonian orogeny. The granitoids of the Rosario Suite represent the main phase of continental arc magmatism that has continuity in other parts of the São Luís Craton and can be correlated with Rhyacian accretionary magmatism in the northwestern portion of the Amazonian Craton that amalgamated Archean terrains during the Transamazonian orogeny.

Geochemical characterization of the source rock intervals, Beni-Suef Basin, West Nile Valley, Egypt

2021 ◽  
Vol 13 (1) ◽  
pp. 1536-1551
Author(s):  
Nader A. A. Edress ◽  
Saudy Darwish ◽  
Amir Ismail
Keyword(s):  
Heat Flow ◽  
Source Rock ◽  
High Heat ◽  
Source Rocks ◽  
Nile Valley ◽  
Peak Oil ◽  
Burial History ◽  
Depth Limit ◽  
Oil Generation ◽  
Rock Depth

Abstract Geochemical and lithological investigations in the WON C-3X well record five organic-matter-rich intervals (OMRIs) of effective source rocks. These OMRIs correspond to moderate and good potentials. Two of these intervals occurred within the L-Kharita member of the Albian age represent 60.97% of the entire Albian thickness. The rest of OMRIs belongs to the Abu-Roash G and F members of the Late Cenomanian–Santonian age comprising 17.52 and 78.66% of their total thickness, respectively. The calculated heat flow of the studied basin is high within the range of 90.1–95.55 mW/m2 from shallower Abu-Roash F to deeper L-Kharita members. This high-heat flow is efficient for shallowing in the maximum threshold expulsion depth in the studied well to 2,000 m and active source rock depth limit to 2,750 m. Thermal maturity and burial history show that the source rock of L-Kharita entered the oil generation from 97 Ma till the late oil stage of 7.5 Ma, whereas the younger Abu-Roash G and F members have entered oil generation since 56 Ma and not reached peak oil yet. Hence, the source rock intervals from Abu-Roash F and G are promising for adequate oil generation.

Pluton source varition over two magmatic pulses in the white-inyo range, central-eastern California : implications for paleozoic and mesozoic tectonic reconstructions

2018 ◽  
Author(s):  
◽  
Elizabeth M Kenderes
Keyword(s):  
Trace Element ◽  
North American ◽  
Oceanic Island ◽  
Island Arc ◽  
Calc Alkaline ◽  
Isotopic Data ◽  
Regional Study ◽  
University Of Missouri ◽  
Tectonic Model ◽  
Central Eastern

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] This dissertation uses compositions of plutons in the White-Inyo Range (WIR) of central-eastern California, which is an important tectonic boundary as it is the easternmost extent of the Mesozoic Cordilleran arc and the western edge of Basin and Range extension. The main goal of this dissertation is to understand the lithospheric structure of this area in relation to the broader regional tectonics. Chapters 2 and 3 specifically investigate the Eureka Valley-Joshua Flat-Beer Creek (EJB) composite arc pluton, from its source to emplacement. The EJB pluton is one of a small number of monzonitic plutons cotemporally emplaced with the primarily calc-alkaline North American Mesozoic Cordilleran arc. Mineral major and trace element compositions are used to show the crystallization sequence and pressures and temperatures of mineral crystallization. These data are used to make interpretations about the EJB pluton's formation from source to emplacement. Additionally, whole rock major and trace element compositions and isotopic data show that the EJB pluton has a unique source from the calc-alkaline plutons: an underplated, eclogitized oceanic island arc. Chapter 4 is a regional study of the WIR, and it includes whole rock major and trace element and isotopic data to interpret the three distinct sources of plutons: (1) the eclogitized oceanic island arc, (2) enriched lithospheric mantle, and (3) Proterozoic North American basement. Recognizing the timing of the generation of these plutons in relation to their sources is crutial to understanding the tectonic history of the WIR area. This dissertation presents tectonic model for western North America from the Early Proterozoic to Late Cretaceous

scholarly journals The Glória quartz-monzodiorite: isotopic and chemical evidence of arc-related magmatism in the central part of the Paleoproterozoic Mineiro belt, Minas Gerais State, Brazil

2006 ◽  
Vol 78 (3) ◽  
pp. 543-556 ◽  
Author(s):  
Ciro A. Ávila ◽  
Wilson Teixeira ◽  
Umberto G. Cordani ◽  
Héctor R. Barrueto ◽  
Ronaldo M. Pereira ◽  
...  
Keyword(s):  
Minas Gerais ◽  
Crustal Material ◽  
Calc Alkaline ◽  
Isotopic Data ◽  
Zircon Age ◽  
Quadrilátero Ferrífero ◽  
Minas Gerais State ◽  
Tectonic Relationship ◽  
Mineralogical Assemblage ◽  
Chemical Evidence

The Glória quartz-monzodiorite, one of the mafic plutons of the Paleoproterozoic Mineiro belt, is intrusive into banded gneisses, amphibolites, schists and phyllites of the Rio das Mortes greenstone belt, in the southern portion of the São Francisco Craton, State of Minas Gerais, Brazil. The Glória quartz-monzodiorite yields a SHRIMP U-Pb zircon age of 2188 ± 29 Ma, suggesting a tectonic relationship with the pre-collisional phase of the Mineiro belt. According to the Nd isotopic evidence (epsilonNd(T) = -3.4; T DM = 2.68 Ga) the original magmas was formed by a mixture among Archean crustal material and Paleoproterozoic juvenile magma. The Glória quartz-monzodiorite shows metaluminous and calc-alkaline tendency with intermediate K content, comparable to that of volcanic-arc rocks. The primary mineralogical assemblage was partly modified by metamorphism, dated between 2131-2121 Ma in nearby coeval plutons. Such metamorphism is significantly older than the reported metamorphic episodes of the Mineiro belt in the Quadrilátero Ferrífero region (2059-2041 Ma) in the eastern portion of the study area. This evidence, together with chemical and isotopic data from other mafic and felsic plutons coeval with the Glória quartz-monzodiorite, indicate a tectonic and magmatic migration within the Mineiro belt from west to east.

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