Sm-Nd isotopes in fine-grained clastic sedimentary materials: Clues to sedimentary processes and recycling growth of the continental crust

2005 ◽  
pp. 287-319 ◽  
Author(s):  
Sam Chaudhuri ◽  
Peter Stille ◽  
Norbert Clauer
Keyword(s):  
Continental Crust ◽  
Nd Isotopes ◽  
Sedimentary Processes ◽  
Fine Grained ◽  
Clastic Sedimentary

Nd isotopes and the origin of 1.9-1.7 Ga Penokean continental crust of the Lake Superior region

1989 ◽  
Vol 101 (3) ◽  
pp. 333-338 ◽  
Author(s):  
KARIN M. BAROVICH ◽  
P. JONATHAN PATCHETT ◽  
ZELL E. PETERMAN ◽  
PAUL K. SIMS
Keyword(s):  
Continental Crust ◽  
Lake Superior ◽  
Nd Isotopes

Geochemistry and geochronology of alkaline dykes from the Finero Phlogopite Peridotite (Ivrea-Verbano Zone): insights into the Triassic-Jurassic tectono-magmatic events of the Southern Alps

2021 ◽  
Author(s):  
Abimbola Chris Ogunyele ◽  
Tommaso Giovanardi ◽  
Mattia Bonazzi ◽  
Maurizio Mazzucchelli ◽  
Alberto Zanetti
Keyword(s):  
Continental Crust ◽  
Southern Alps ◽  
Coarse Grained ◽  
Dyke Swarm ◽  
Fine Grained ◽  
Sector Zoning ◽  
Magmatic Stage ◽  
Late Magmatic Stage ◽  
Mesozoic Magmatism ◽  
Peridotite Mantle

<p>The Ivrea-Verbano Zone (IVZ, westernmost sector of the Southern Alps) represents a unique opportunity to investigate the Paleozoic to Mesozoic geodynamic evolution of the Gondwana and Laurasia boundary from the perspective of the lower continental crust. Only recently, the petrochemical record of Triassic-Jurassic magmatism has been recognized. It mainly affected the northernmost tip, the Finero Complex, where the continental crust was tectonically thinned before opening of Alpine Tethys. However, the Mesozoic magmatism in the Finero Complex is still poorly-constrained. Firstly, its extent is largely unknown, because the mantle and crustal intrusives were already enriched by Paleozoic processes. Secondly, Mesozoic melts migration started when the Finero Complex was still placed at P-T conditions typical of a continental crust-mantle transition (1 GPa): this has promoted the reopening of the geochronological clocks in both Paleozoic and Mesozoic rocks, which usually provides wide time intervals. Lastly, the finding of Mesozoic magmatism as composite veins/pods and metasomatised layers has not allowed an exhaustive reconstruction of the primitive melts geochemistry. To place further constraints on such issue, a new dyke swarm cropping out in the Finero Phlogopite Peridotite mantle unit has been investigated. Dykes usually cut at high angle the mantle foliation and are up to 60 cm thick. They are composed by coarse-grained hornblendite to anorthosite, both phlogopite/biotite-bearing. Many dykes are composite, showing variable proportions of hornblendite and anorthosite. In places, the dyke swam was affected by volatiles overpressure as late magmatic stage, which produced plastic flow and development of a porphyroclastic structure by deformation of the early cumulates, with widespread segregation of a fine-grained mica matrix.</p><p>Dykes mainly consist of pargasite, phlogopite/biotite, albite (An 8-10), in association with apatite, monazite, ilmenite, zircon, Nb-rich oxides, carbonates. Enrichments in Fe (amphibole and biotite) and Na (plagioclase) suggest segregation from evolved melts, strongly enriched in H<sub>2</sub>O, P, C. The large LILE and LREE contents in amphiboles, sometimes associated to high Nb, Ta, Zr and Hf concentrations, as well as the mineral assemblage, support an alkaline affinity of the melts. The strongly positive εHf<sub>t </sub>(+10) of zircons and the isotopic Sr composition of amphiboles (0.7042) point to a derivation of the melts from mildly enriched sources, possibly located at the crust-mantle interface.</p><p>Zircons from anorthosite layers are mostly anhedral fragments. They show homogenous internal structure or sector zoning. Concordant <sup>206</sup>Pb/<sup>238</sup>U zircon ages vary from 221 ± 9 Ma to 192 ± 8 Ma. The results of this study confirm that mantle input to the Southern Alps magmatism was of alkaline affinity from Norian to Sinemurian. A widespread fluids circulation induced by such magmatism at high P-T conditions was likely the main cause of the diffuse geochronological reset towards Mesozoic ages of the northern IVZ.</p>

scholarly journals Multiple sources and magmatic evolution of the Late Triassic Daocheng batholith in the Yidun Terrane: Implications for evolution of the Paleo-Tethys Ocean in the eastern Tibetan Plateau

2021 ◽  
Author(s):  
Pengsheng Dong ◽  
Guochen Dong ◽  
M. Santosh ◽  
Xuanxue Mo ◽  
Peng Wang ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Chemical Diffusion ◽  
Late Triassic ◽  
Eastern Tibetan Plateau ◽  
Multiple Sources ◽  
Nd Isotopes ◽  
Fine Grained ◽  
Tethys Ocean ◽  
T Values ◽  
Lower Crustal

Granitoids with diverse composition and tectonic settings provide important tools for exploring crustal evolution and regional geodynamic history. Here we present an integrated study using petrological, mineralogical, zircon U-Pb geochronological, whole-rock geochemical, and isotopic data on the Late Triassic Daocheng batholith in the Yidun Terrane with a view to understanding the petrogenesis of a compositionally diverse batholith and its implications for the evolution of the Paleo-Tethys Ocean in the eastern Tibetan Plateau. The different lithological units of the batholith, including granodiorite, monzogranite, and quartz diorite, with abundant mafic microgranular enclaves in the granodiorite (MME I) and monzogranite (MME II), show identical crystallization ages of 218−215 Ma. The mineral assemblage and chemical composition of the granodiorite are identical to those of tonalitic-granodioritic melts generated under water-unsaturated conditions. The insignificant Eu anomalies and low magmatic temperatures indicate hydrous melting in the source. The relatively narrow range of whole-rock chemical and Sr-Nd isotopes, as well as the zircon trace element and Hf isotopic compositions of the granodiorite, suggest a homogeneous crustal source for the magma. Our modeling suggests that the rock was produced by 20−50% of lower crustal melting. The Daocheng monzogranites display more evolved compositions and larger variations in Sr-Nd-Hf isotopes than the granodiorite, which are attributed to assimilation and the fractional crystallization process. This is evidenced by the presence of metasedimentary enclave and inherited zircon grains with Neoproterozoic and Paleozoic ages, a non-cotectic trend in composition, and the trend shown by the modeling of initial 87Sr/86Sr ratios and Sr. The quartz diorites and MMEs showing composition similar to that of andesitic primary magma have high zircon εHf(t) values and are characterized by enrichment in LILEs and depletion of HFSEs. They were derived from the partial melting of lithospheric mantle that had been metasomatized by slab melts and fluids. The MMEs in both rocks display typical igneous texture and higher rare earth element (REE) and incompatible element concentrations than their host granites. The presence of fine-grained margins, acicular apatite, and plagioclase megacrysts suggests a magma mingling process. The overgrowth of amphibole around the pyroxene, quartz ocelli rimmed by biotite, and oscillatory zones of plagioclase are all indicative of chemical diffusion. Their enriched Sr-Nd isotopes imply isotopic equilibrium with the host granites. Based on a comparison with the coeval subduction-related magmatism, we propose that subduction and subsequent rollback of the Paleo-Tethys (Garzê-Litang Ocean) oceanic slab was the possible mechanism that triggered the diverse Triassic magmatism within the eastern Tibetan Plateau.

A low-relief hill in eastern Ontario, Canada, covered by the easily erodible Queenston Formation and derived sediments — probably the result of Quaternary tectonic uplift

2014 ◽  
Vol 51 (9) ◽  
pp. 862-876
Author(s):  
J.L. Wallach
Keyword(s):  
Magnetic Anomaly ◽  
Surface Expression ◽  
Tectonic Uplift ◽  
Unconsolidated Sediments ◽  
Upper Ordovician ◽  
Apparent Contradiction ◽  
Fine Grained ◽  
The North ◽  
Clastic Sedimentary ◽  
The Hill

The Upper Ordovician Queenston Formation is predominantly a brick red, easily erodible, fine-grained clastic sedimentary rock that is not expected to form topographic highs. Nevertheless, the Queenston, overlain by a relatively thin cover of red unconsolidated sediments derived from it, blankets two low-relief hills. Their combined presence at the top of those hills is curious; therefore, Cholowski Hill, the larger of the two, and its surroundings were studied to try to resolve that apparent contradiction. Cholowski Hill is elongated nearly north–south and overlies a similarly shaped, north–south magnetic anomaly, which is a spur off a generally north-northeast-trending magnetic high. The spatial and geometric relationships of the hill to the magnetic anomaly, a feature of the Precambrian basement, suggest that the hill resulted from repeated tectonic uplift along faults that propagated upward from the basement, though many of them show no surface expression. Two notable exceptions are the North Russell and East Ridge faults that are topographically expressed at the surface and extend along the spine of Cholowski Hill. Their presence and that of Cholowski Hill imply geologically recent uplift. Glacial erratics on, and the smooth character of, the hill imply that it had been overridden by continental ice and was an upland prior to at least the last major glacial advance. Champlain Sea sediments surrounding and encroaching on the lowest part of the hill, but absent from the higher elevations, intimate that Cholowski Hill was not completely covered by those sediments, though it is conceivable that deposited sediments were washed away. The precise age of uplift is unknown, but the characteristics of the hill suggest a Quaternary event.

The Mackenzie Delta: sedimentary processes and facies of a high-latitude, fine-grained delta

Sedimentology ◽  
2001 ◽  
Vol 48 (5) ◽  
pp. 1047-1078 ◽  
Author(s):  
Philip R. Hill ◽  
C. Peter Lewis ◽  
Simon Desmarais ◽  
Vassen Kauppaymuthoo ◽  
Hasna Rais
Keyword(s):  
High Latitude ◽  
Mackenzie Delta ◽  
Sedimentary Processes ◽  
Fine Grained

Sr-Nd isotopes as tracers of fine-grained detrital sediments: the South-Barbados accretionary prism during the last 150 kyr

1997 ◽  
Vol 136 (3-4) ◽  
pp. 225-243 ◽  
Author(s):  
Mario Parra ◽  
Jean-Claude Faugères ◽  
Francis Grousset ◽  
Claude Pujol
Keyword(s):  
Accretionary Prism ◽  
The South ◽  
Nd Isotopes ◽  
Fine Grained

Pb–Zn occurrences and their Pb-isotopic signatures bearing on metallogeny and mineral exploration—Paleozoic sedimentary rocks, northern Appalachians, Quebec

1988 ◽  
Vol 25 (11) ◽  
pp. 1777-1790 ◽  
Author(s):  
K. Schrijver ◽  
E. Marcoux ◽  
G. Beaudoin ◽  
J. Y. Calvez
Keyword(s):  
Continental Crust ◽  
Mineral Exploration ◽  
Sedimentary Rocks ◽  
Isotope Ratios ◽  
Isotopic Signature ◽  
Coarse Grained ◽  
Pb Isotope ◽  
Isotopic Signatures ◽  
Fine Grained ◽  
Quartz Veins

Galena Pb-isotope ratios of epithermal vein and disseminated sulfide occurrences in the Taconian Orogen and Siluro-Devonian basin cluster around 17.90–18.05 for 206Pb/204Pb and 37.70–38.00 for 208Pb/204Pb. The major source of Pb in most, if not all, occurrences is a fairly common continental crust, a characteristic found in published analyses of Grenville feldspar Pb. A southwest to northeast increase in galena 206Pb/204Pb ratios is ascribed to the supply of several types of detritus from Grenville basement during the Cambro-Ordovician: coarse-grained, K-feldspar-bearing in the southwest, grading into fine-grained phyllitic, and relatively more highly radiogenic in the northeast.Emplacement (i) of Pb–Zn–barite veins and disseminations, commonly of homogeneous crustal Pb-isotopic signature, was late Taconian; (ii) of Pb–Zn–quartz veins, of less homogeneous signature, was post-Taconian; and (iii) of Pb–Zn–carbonate veins, relatively highly radiogenic and commonly homogeneous, was late or post-Acadian. Signatures of the first-mentioned group seem to be most useful in exploration.

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