Lu–Hf zircon and Sm–Nd whole-rock isotope constraints on the extent of juvenile arc crust in Avalonia: examples from Newfoundland and Nova Scotia, Canada

2015 ◽  
Vol 52 (3) ◽  
pp. 161-181 ◽  
Author(s):  
J.C. Pollock ◽  
P.J. Sylvester ◽  
S.M. Barr
Keyword(s):  
Isotope Composition ◽  
Volcanic Rocks ◽  
Detrital Zircons ◽  
Isotopic Signatures ◽  
Magmatic Arc ◽  
Depleted Mantle ◽  
Felsic Volcanic ◽  
Clastic Sedimentary ◽  
Neoproterozoic Magmatic Arc

Avalonia, the largest accreted crustal block in the Appalachian orogen, consists of Neoproterozoic magmatic arc sequences that represent protracted and episodic subduction-related magmatism before deposition of an Ediacaran–Ordovician cover sequence including siliciclastic rocks. Zircon crystals were obtained from arc-related magmatic rocks and from clastic sedimentary sequences and analyzed in situ for their Hf-isotope composition. The majority of magmatic and detrital zircons are dominated by initial 176Hf/177Hf values that are more radiogenic than chondritic uniform reservoir (CHUR) with calculated crust formation Hf–TDM model ages that range from 0.84 to 1.30 Ga. These results suggest formation by partial melting of juvenile mantle in a Neoproterozoic continental arc. Some zircons have Hf–TDM model ages ca. 1.39–3.09 Ga with εHf values of –33.9 to –0.5 and more clearly indicate involvement of older lithosphere in their petrogenesis. Whole-rock Sm–Nd isotopic compositions from felsic volcanic rocks are characterized by positive initial εNd values with Mesoproterozoic depleted mantle model ages consistent with juvenile extraction. Results suggest a dominant mantle component with long-term light rare earth element (LREE) depletion mixed with an older crustal component with long-term LREE enrichment. The pattern of TDM model ages and variations in Lu–Hf and Sm–Nd isotopic character are compatible with a ca. 1.0–1.2 Ga igneous tectonomagmatic event that formed basement to Neoproterozoic magmatic arcs in Avalonia. The presence of evolved isotopic signatures, however, indicates that significant older Proterozoic crust is present locally beneath Avalonia, suggesting that Avalonia formed in a single Neoproterozoic arc system that generated juvenile mantle-derived crust, coupled with lesser anatectic reworking of significantly older crust.

Geochemistry and tectonic discrimination of Late Proterozoic arc-related volcaniclastic turbidite sequences, Antigonish Highlands, Nova Scotia

1993 ◽  
Vol 30 (12) ◽  
pp. 2273-2282 ◽  
Author(s):  
J. Brendan Murphy ◽  
Deborah L. MacDonald
Keyword(s):  
Nova Scotia ◽  
Tectonic Setting ◽  
Volcanic Rocks ◽  
Sedimentary Rocks ◽  
Widespread Application ◽  
Isotopic Signatures ◽  
Late Proterozoic ◽  
Felsic Volcanic ◽  
Clastic Sedimentary ◽  
End Members

The Late Proterozoic (ca. 618–610 Ma) Georgeville Group of northern mainland Nova Scotia lies within the Avalon Composite Terrane and consists of subgreenschist- to greenschist-facies mafic and felsic volcanic rocks overlain by volcaniclastic turbidites that were deposited in an ensialic basin within a rifted volcanic arc. Geochronological data indicate that the volcanic and sedimentary rocks are coeval. The geochemical and isotopic signatures of the sedimentary rocks are attributed to erosion of the coeval Avalonian volcanic rocks that flank the basin and are consistent with synorogenic deposition. There is no evidence of significant chemical contribution from Avalonian basement.Knowledge of the tectonic setting facilitates the testing of published geochemical discriminant diagrams for clastic sedimentary rocks. Discrimination diagrams using ratios such as K2O/Na2O and Al2O3/(CaO + Na2O) give inconclusive results, probably due to elemental mobility during secondary processes. Plots involving MgO, TiO2, and Fe2O3 detect the chemical contribution of mafic detritus, give much tighter clusters of data, and plot between Aleutian- and Cascade-type arc-derived sediments, suggesting a moderate thickness of continental crust beneath the arc.The arc-related signature of the Georgeville sedimentary rocks is clearly recognizable on ternary plots involving inter-element ratios of high field strength elements (e.g., Ti–Y–Zr, Nb–Y–Zr, and Hf–Ta–Th) in which the samples plot as mixing trends between mafic and felsic end members. Diagrams of this type may have widespread application to tectonic discrimination of sedimentary rocks because in most suites these ratios are relatively insensitive to sedimentary and metamorphic processes.

Nd- and Sr-isotope systematics for the Kamiskotia–Montcalm area: implications for the formation of late Archean crust in the western Abitibi Subprovince, Canada

1991 ◽  
Vol 28 (1) ◽  
pp. 58-76 ◽  
Author(s):  
C. Tucker Barrie ◽  
Steven B. Shirey
Keyword(s):  
Greenstone Belt ◽  
Volcanic Rocks ◽  
Isotopic Signatures ◽  
Tectonic Model ◽  
Depleted Mantle ◽  
Lree Enrichment ◽  
Abitibi Subprovince ◽  
Mantle Reservoir ◽  
Element Enrichment

Geochemistry and Nd isotopic compositions are used to characterize mantle and crustal sources and to provide constraints on petrogenetic models for tholeiitic, calc-alkalic, and lamprophyric suites in the Kamiskotia–Montcalm area. The Kamiskotia gabbroic complex (KGC) and cogenetic, bimodal volcanic rocks have εNd(t) = +2.2 to +2.6, consistent with a direct derivation from a long-term, light rare-earth element (LREE)-depleted mantle. The Montcalm gabbroic complex has decreasing εNd(t) upsection from +2.8 to +1.0, consistent with contamination by long-term, LREE-enriched (with respect to the long-term, LREE-depleted Abitibi mantle) crust during fractionation. Two calc-alkalic lamprophyre samples, characterized by large-ion lithophile element (LILE) and LREE enrichment and high MgO, Ni, and Cr contents, have εNd(t) of +2.5 and +2.8, indicating a derivation from a depleted mantle source that had undergone recent trace-element enrichment. A different lamprophyre suite is extremely LILE and LREE enriched and has an εNd(t) of +1.0, indicating a derivation from a slightly different source that had earlier LREE enrichment. Granitoid rocks internal and external to greenstone belt rocks have εNd(t) = +2.5 to +3.8 and +0.6 to −0.4, respectively. The lower values provide additional evidence for the existence of LREE-enriched crust in this area.Considering these data along with other radiogenic isotope studies, a petrogenetic and tectonic model is suggested for the crustal development of the southern Abitibi Subprovince. From >2740 to 2698 Ma—the major period of volcanic activity—komatiitic and tholeiitic suites and one lamprophyre suite were derived from a uniformly LREE-depleted mantle reservoir with εNd(t) = +2 to +3. Calc-alkalic granitoids were emplaced generally after 2700 Ma. Their long-term, LREE-depleted and LREE-enriched Nd isotopic signatures are similar to signatures in continental-arc settings (e.g., the Coastal Batholith of Peru). Form 2690 to 2670 Ma, when transpressional tectonism prevailed, mantle-derived magmatism was represented by long-term, LREE-enriched (εNd(t) = +1 to +2) lamprophyric and alkalic volcanic suites.The Kamiskotia suite has a seven-point, whole-rock – mineral isochron Sm–Nd age of 2710 ± 30 Ma, identical to U–Pb zircon ages for the suite, indicating closed-system behavior. An Rb–Sr mineral – whole-rock isochron age from one KGC sample is 2450 ± 30 Ma, identical to U–Pb ages for the Hearst–Matachewan dike swarm, a prominent feature in the KGC area. Regression of whole-rock and mineral-isotope data for one granitoid sample with a U–Pb zircon age of 2696 ± 1.5 Ma gives identical ages of 2530 ± 30 Ma in the Sm–Nd and Rb–Sr systems. The latter data add to an increasing body of evidence for cryptic, late thermal events after granitoid–greenstone belt development in the southern Abitibi Subprovince.

Geochemistry and Isotope Composition of Paleoproterozoic Granites and Felsic Volcanics of the Elash Graben: Evidence of the Heterogeneity of the Early Precambrian Crust

2021 ◽  
Vol 62 (10) ◽  
pp. 1175-1187
Author(s):  
A.D. Nozhkin ◽  
O.M. Turkina ◽  
K.A. Savko
Keyword(s):  
Isotope Composition ◽  
Volcanic Rocks ◽  
Rare Metal ◽  
Temporal Association ◽  
Metal Deposit ◽  
Wide Range ◽  
Rare Metal Deposit ◽  
Geochronological Study ◽  
Felsic Volcanic ◽  
Felsic Volcanic Rocks

Abstract —The paper presents results of a petrogeochemical and isotope–geochronological study of the granite–leucogranite association of the Pavlov massif and felsic volcanics from the Elash graben (Biryusa block, southwest of the Siberian craton). A characteristic feature of the granite–leucogranites is their spatial and temporal association with vein aplites and pegmatites of the East Sayan rare-metal province. The U–Pb age of zircon from granites of the Pavlov massif (1852 ± 5 Ma) is close to the age of the pegmatites of the Vishnyakovskoe rare-metal deposit (1838 ± 3 Ma). The predominant biotite porphyritic granites and leucogranites of the Pavlov massif show variable alkali ratios (K2O/Na2O = 1.1–2.3) and ferroan (Fe*) index and a peraluminous composition; they are comparable with S-granites. The studied rhyolites of the Tagul River (SiO2 = 71–76%) show a low ferroan index, a high K2O/Na2O ratio (1.6–4.0), low (La/Yb)n values (4.3–10.5), and a clear Eu minimum (Eu/Eu* = 0.3–0.5); they are similar to highly fractionated I-granites. All coeval late Paleoproterozoic (1.88–1.85 Ga) granites and felsic volcanics of the Elash graben have distinct differences in composition, especially in the ferroan index and HREE contents, owing to variations in the source composition and melting conditions during their formation at postcollisions extension. The wide range of the isotope parameters of granites and felsic volcanic rocks (εNd from +2.0 to –3.7) and zircons (εHf from +3.0 to +0.8, granites of the Toporok massif) indicates the heterogeneity of the crustal basement of the Elash graben, which formed both in the Archean and in the Paleoproterozoic.

Biology and Management of Dogfish Sharks

2009 ◽  
Keyword(s):  
Stable Isotope ◽  
Isotope Composition ◽  
Feeding Habits ◽  
Important Species ◽  
Isotopic Signatures ◽  
Ecological Changes ◽  
Varied Diet ◽  
Commercially Important ◽  
C And N

Abstract.—Spiny dogfish <em>Squalus acanthias </em>are an abundant and commercially important species of fish off both the Atlantic and Pacific coasts of North America. They are opportunistic feeders and have a varied diet that can include many fish species, especially small forage fish such as herring, capelin, and sand lance as well as crustaceans, worms, euphausiids, gelatinous zooplankton, and cephalopods. The purpose of our present study is to investigate the utility of the second dorsal spine in providing multiyear information on the feeding habits of dogfish using stable isotope (C and N) analysis. The outer dentine and enamel layers of a spine from three dogfish (caught off the coast of British Columbia) were analyzed to obtain their stable nitrogen and carbon isotope composition (δ<sup>15</sup>N and δ<sup>13</sup>C, respectively). Each sample had annuli from multiple years, allowing possible seasonal migrations to be averaged over samples. The δ<sup>15</sup>N ranged from a low of 11.6‰ to a high of 14.9‰ over the three spines and δ<sup>13</sup>C ranged from –11.5‰ to –18.4‰. The variable isotopic signatures along the spine indicate that the method may be used to assess ecological changes. Stable isotope measurements of dogfish spines could be a valuable means of determining long-term changes in habitat usage and feeding ecology.

Coeval sedimentation, magmatism, and fold-thrust belt development in the Trans-Hudson Orogen: geochronological evidence from the Wekusko Lake area, Manitoba, Canada

1999 ◽  
Vol 36 (2) ◽  
pp. 293-312 ◽  
Author(s):  
Kevin M Ansdell ◽  
Karen A Connors ◽  
Richard A Stern ◽  
Stephen B Lucas
Keyword(s):  
Regional Metamorphism ◽  
Volcanic Rocks ◽  
Sedimentary Rocks ◽  
Detrital Zircons ◽  
Lake Area ◽  
Thrust Belt ◽  
Fold And Thrust Belt ◽  
Minimum Age ◽  
Flin Flon ◽  
Felsic Volcanic

Lithological and structural mapping in the east Wekusko Lake area of the Flin Flon Belt, Trans-Hudson Orogen, suggested an intimate relationship between magmatism, fluvial sedimentation, and initiation of fold and thrust belt deformation. Conventional U-Pb geochronology of volcanic rocks in fault-bounded assemblages provides a minimum age of 1876 ± 2 Ma for McCafferty Liftover back-arc basalts, and ages of between 1833 and 1836 Ma for the Herb Lake volcanic rocks. A rhyolite which unconformably overlies Western Missi Group fluvial sedimentary rocks has complex zircon systematics. This rock may be as old as about 1856 Ma or as young as 1830 Ma. The sedimentary rocks overlying this rhyolite are locally intercalated with 1834 Ma felsic volcanic rocks, and yield sensitive high resolution ion microprobe (SHRIMP) U-Pb and Pb-evaporation detrital zircon ages ranging from 1834 to 2004 Ma. The Eastern Missi Group is cut by an 1826 ± 4 Ma felsic dyke, and contains 1832-1911 Ma detrital zircons. The dominant source for detritus in the Missi Group was the Flin Flon accretionary collage and associated successor arc rocks. The fluvial sedimentary rocks and the Herb Lake volcanic rocks were essentially coeval, and were then incorporated into a southwest-directed fold and thrust belt which was initiated at about 1840 Ma and active until at least peak regional metamorphism.

Chapter 4 Paleoproterozoic (2.0–1.8 Ga) syn-orogenic sedimentation, magmatism and mineralization in the Bothnia–Skellefteå lithotectonic unit, Svecokarelian orogen

2020 ◽  
Vol 50 (1) ◽  
pp. 83-130 ◽  
Author(s):  
Pietari Skyttä ◽  
Pär Weihed ◽  
Karin Högdahl ◽  
Stefan Bergman ◽  
Michael B. Stephens
Keyword(s):  
Volcanic Rocks ◽  
Shear Zones ◽  
Low Grade ◽  
Lower Grade ◽  
Magmatic Arc ◽  
The North ◽  
Magmatic Rocks ◽  
Structural Style ◽  
Volcanogenic Massive Sulphide ◽  
Felsic Volcanic

AbstractThe Bothnia–Skellefteå lithotectonic unit is dominated by turbiditic wacke and argillite (Bothnian basin), deposited at 1.96 (or older)–1.86 Ga, metamorphosed generally under high-grade conditions and intruded by successive plutonic suites at 1.95–1.93, 1.90–1.88, 1.87–1.85 and 1.81–1.76 Ga. In the northern part, low-grade and low-strain, 1.90–1.86 Ga predominantly magmatic rocks (the Skellefte–Arvidsjaur magmatic province) are enclosed by the basinal components. Subduction-related processes in intra-arc basin and magmatic arc settings, respectively, are inferred. Changes in the metamorphic grade and the relative timing of deformation and structural style across the magmatic province are linked to major shear zones trending roughly north–south and, close to the southern margin, WNW–ESE. Zones trending WNW–ESE and ENE–WSW dominate southwards. Slip along the north–south zones in an extensional setting initiated synchronously with magmatic activity at 1.90–1.88 Ga. Tectonic inversion steered by accretion to a craton to the east, involving crustal shortening, ductile strain and crustal melting, occurred at 1.88–1.85 Ga. Deformation along shear zones under lower-grade conditions continued at c. 1.8 Ga. Felsic volcanic rocks (1.90–1.88 Ga) host exhalative and replacement-type volcanogenic massive sulphide deposits (the metallogenic Skellefte district). Other deposits include orogenic Au, particularly along the ‘gold line’ SW of this district, porphyry Cu–Au–Mo, and magmatic Ni–Cu along the ‘nickel line’ SE of the ‘gold line’.

Age and source of detrital zircons from the Missi Formation: a Proterozoic molasse deposit, Trans-Hudson Orogen, Canada

1992 ◽  
Vol 29 (12) ◽  
pp. 2583-2594 ◽  
Author(s):  
Kevin M. Ansdell ◽  
T. Kurtis Kyser ◽  
Mel R. Stauffer ◽  
Garth Edwards
Keyword(s):  
Volcanic Rocks ◽  
Sedimentary Rocks ◽  
Detrital Zircons ◽  
Early Proterozoic ◽  
Minimum Age ◽  
Granitoid Rocks ◽  
Evaporation Technique ◽  
Single Zircon ◽  
Flin Flon ◽  
Felsic Volcanic

The Missi Formation in the Flin Flon Basin forms part of a discontinuous series of molasse-type sediments found throughout the Early Proterozoic Trans-Hudson Orogen in northern Saskatchewan and Manitoba. The Flin Flon Basin contains a sequence of proximal-fan to braided-stream fluvial conglomerates and sandstones, which unconformably overlie subaerially weathered Amisk Group volcanic rocks. Stratigraphic way-up indicators have been preserved, even though these rocks have undergone greenschist-facies metamorphism and polyphase deformation. The sedimentary rocks are crosscut by intrusive rocks, which provide a minimum age of sedimentation of 1840 ± 7 Ma.Detrital zircons from each of the six stratigraphic subdivisions of the Flin Flon Basin were analyzed using the single-zircon Pb-evaporation technique. Euhedral to slightly rounded zircons dominate each sample, and these zircons give ages of between about 1854 and 1950 Ma. The Missi sediments were thus deposited between 1840 and 1854 Ma. Possible sources for the detrital zircons are Amisk Group felsic volcanic rocks and post-Amisk granitoid rocks and orthogneisses in adjacent domains within the Trans-Hudson Orogen. However, the immature character of the sedimentary rocks, the composition of clasts, the euhedral character of many of the zircons, and the range in ages suggest that most were likely derived from Amisk Group and granitoid rocks in the western Flin Flon Domain. Rounded zircons are uncommon but provide evidence for the reworking of older Proterozoic sedimentary rocks, or a distant Archean or Early Proterozoic granitoid terrane.

Geochemistry and isotope studies of the metavolcanic rocks of Shimoga greenstone belt, Western Dharwar craton - an effort to deduce the Petrogenesis.

2020 ◽  
Author(s):  
Anshuman Giri ◽  
Rajagopal Anand
Keyword(s):  
Fractional Crystallization ◽  
Greenstone Belt ◽  
Active Continental Margin ◽  
Volcanic Rocks ◽  
Crustal Contamination ◽  
Dharwar Craton ◽  
Metavolcanic Rocks ◽  
Depleted Mantle ◽  
Felsic Volcanic ◽  
Felsic Volcanic Rocks

&lt;p&gt;The archaean greenstone belts, dominated by mafic to felsic volcanic rocks followed by younger granitic intrusions occurs associated with volcano-sedimentary sequences. The Dharwar Super group (2600 to 2900 Ma) of rocks in western Dharwar craton, underlie the older TTG gneisses. The Shimoga greenstone belt (SGB) of WDC constitute the basal polymictic conglomerate along with quartzite, pyroclastic rocks, carbonaceous rocks, greywacke-argillite sequences with a thick pile of mafic and felsic metavolcanic rocks (BADR). These rocks are suffered from greenschist to lower amphibolite grade of metamorphism. The Medur metavolcanic volcanic rocks give an age of 2638 &amp;#177; 66 Ma (1), whereas the Daginakatte felsic volcanic rocks give an age of 2601 &amp;#177; 6 Ma (2). The present studied age of 2638 &amp;#177; 66 Ma, tells about the cessation of mafic magmatism in WDC. The metavolcanic rocks of the Medur formation are tholeiitic to calc-alkaline in nature. These rocks show flat to LREE enriched REE pattern with negative europium anomaly. And also show enrichment in LILE and depletion in HFSE elements with significant Nb-Ta anomaly. The geochemical and the isotope data suggest the involvement of partial melting of the depleted mantle by the slab components and assimilation fractional crystallization (AFC) processes for the magma generation. The SGB metavolcanic rocks have 143Nd/144Nd ratios (0.511150 to .513076) and &amp;#949;Nd values of -3.1 to -5.5 and the negative &amp;#949;Nd values &amp;#160;for the rocks is due to the crustal contamination of the magma in a shallow marine subduction setting. The parental magmas were derived from melting in the mantle wedge fluxed by slab derived fluids and slab components followed by assimilation fractional crystallization (AFC) processes involving continental crust in an active continental margin.&lt;/p&gt;&lt;ul&gt;&lt;li&gt;(1) Giri et al., 2019. Lithos, &lt;strong&gt;330-331&lt;/strong&gt;, 177-193&lt;/li&gt; &lt;li&gt;(2) Trendall et al., 1997a. J. Geol. Soc. India, &lt;strong&gt;50&lt;/strong&gt;, 25-50.&lt;/li&gt; &lt;/ul&gt;

U–Pb zircon geochronology of Lower Jurassic and Paleozoic Stikinian strata and Tertiary intrusions, northwestern British Columbia

1995 ◽  
Vol 32 (8) ◽  
pp. 1155-1171 ◽  
Author(s):  
C. J. Greig ◽  
G. E. Gehrels
Keyword(s):  
Volcanic Rocks ◽  
Lower Jurassic ◽  
Detrital Zircons ◽  
Zircon Geochronology ◽  
Fold Belt ◽  
Isotopic Data ◽  
The West ◽  
Juvenile Crust ◽  
Felsic Volcanic ◽  
Felsic Volcanic Rocks

New U–Pb zircon ages are reported from western Stikinia. Devonian and Pennsylvanian ages of volcanic rocks at Oweegee dome confirm the presence of pre-Permian strata, and with Paleozoic and Triassic detrital zircons from Lower Jurassic sandstone, they help to demonstrate pre-Lower Jurassic deformation and uplift. The absence of pre-Paleozoic inherited zircon from all samples is consistent with Nd–Sr isotopic data which suggest that Stikinia consists mainly of juvenile crust. U–Pb ages for posttectonic intrusions suggest that structures in Skeena Fold Belt in the Kinskuch area formed prior to Eocene time. Five ages for felsic volcanic rocks from stratigraphically well-constrained upper parts of the Hazelton arc are approximately 196–199 Ma and suggest near-contemporaneity for cessation of volcanism in the areas studied. The Sinemurian or late Sinemurian – early Pliensbachian ages are older than previously reported U–Pb and biostratigraphic ages for presumed correlative rocks to the west, and westward-migrating volcanism is implied. Together with Toarcian fossils from overlying sandstone, the new ages suggest that a hiatus of moderate duration preceded regionally extensive sedimentation.

Neodymium isotope geochemistry of felsic volcanic and intrusive rocks from the Yukon–Tanana Terrane in the Finlayson Lake Region, Yukon, Canada

2003 ◽  
Vol 40 (1) ◽  
pp. 77-97 ◽  
Author(s):  
Stephen J Piercey ◽  
James K Mortensen ◽  
Robert A Creaser
Keyword(s):  
Isotope Geochemistry ◽  
Volcanic Rocks ◽  
Lake Region ◽  
Volcanogenic Massive Sulphide ◽  
Depleted Mantle ◽  
Intrusive Rocks ◽  
Felsic Volcanic ◽  
Back Arc ◽  
Finlayson Lake ◽  
Felsic Rocks

Devonian–Mississippian felsic rocks from the Finlayson Lake region have variable geochemical and Nd isotopic characteristics that provide insights into the tectonic and metallogenic evolution of the Yukon–Tanana terrane (YTT), and the northern Cordillera. Late Devonian (~365–360 Ma) calc-alkaline and tholeiitic arc felsic rocks in the mafic-dominated Fire Lake unit yield εNd350 = –4.8 and +0.1, respectively, and have 1.49–1.94 Ga depleted mantle model ages (TDM). Devonian–Mississippian (~360–356 Ma) felsic volcanic (Kudz Ze Kayah unit, Wolverine succession) and intrusive rocks (Grass Lakes suite) associated with volcanogenic massive sulphide (VMS) deposits have εNd350 = –7.8 to –9.5 with TDM = 1.59–2.25 Ga. A granitoid sample from the Early Mississippian (~350–345 Ma) Simpson Range plutonic suite has εNd350 = –12.9 and TDM = 2.01 Ga, similar to previously reported values for this suite. The VMS-associated Grass Lakes suite of granitoids has higher high field strength element (HFSE) and rare-earth element (REE) contents, and higher Zr/Sc, Zr/TiO2, Nb/La, and Zr/La values relative to the Simpson Range plutonic suite; these geochemical features are similar to coeval VMS-associated felsic volcanic rocks in the Kudz Ze Kayah unit. The identification of similar HFSE–REE-enriched felsic volcanic and subvolcanic intrusive rocks may aid in delineating prospective regions for VMS mineralization in the YTT and other continental-margin arc to back-arc environments. The geochemical and Nd isotopic data for these YTT felsic rocks suggest that they reflect episodic mid-Paleozoic arc (Fire Lake unit; Simpson Range plutonic suite) and back-arc magmatism (Kudz Ze Kudz unit; Wolverine succession) built upon a transitional basement with variable, but significant, influence from evolved (Proterozoic) crustal materials.

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