Crust–mantle interaction in western Turkey: implications from Sr and Nd isotope geochemistry of Tertiary and Quaternary volcanics

1991 ◽  
Vol 128 (5) ◽  
pp. 417-435 ◽  
Author(s):  
N. Güleç
Keyword(s):  
Trace Element ◽  
Isotope Geochemistry ◽  
Major And Trace Elements ◽  
Crustal Material ◽  
Calc Alkaline ◽  
Western Turkey ◽  
Alkaline Rocks ◽  
Trace Element Chemistry ◽  
Depleted Mantle ◽  
Lower Crustal

AbstractThe isotopic composition of Sr and Nd together with the abundance data for major and trace elements are reported for Tertiary to Quaternary volcanics from a variety of localities in western Turkey. These data are used to evaluate the role of crust–mantle interaction in the petrogenesis of the western Turkish volcanics. The major and trace element chemistry reveals a general change in the nature of volcanism from dominantly calc-alkaline in Tertiary to alkaline in Quaternary times. The calc-alkaline rocks are quartz-normative and comprise andesitic to rhyolitic compositions of Miocene–Pliocene age; the trace element patterns are typical of continental margin volcanics with high Ba/Nb ratios and negative Ti anomalies. The alkaline rocks are nepheline-normative and dominantly Quaternary in age; they are basic in composition, with a change from potassic nature in Miocene–Pliocene to sodic in Quaternary times. Most of the Tertiary alkaline volcanics display trace element patterns similar to those of the calc-alkaline ones, whereas the Quaternary alkaline volcanics have low Ba/Nb ratios without negative Ti anomalies; they resemble intraplate volcanics.The calc-alkaline rocks have high87Sr/86Sr (from 0.705011 to 0.709529) and low143Nd/144Nd ratios (from 0.512294 to 0.512691). With the exception of two Tertiary samples, all the alkaline volcanics plot within the so-called mantle array of the isotope correlation diagram,87Sr/86Sr ratios ranging from 0.703128 to 0.703628 and143Nd/144Nd ratios ranging from 0.512749 to 0.512998. The two Tertiary alkaline samples, with trace element patterns similar to those of the calc-alkaline ones, have considerably higher Sr (0.707741–0.707918) and lower Nd (0.512494–0.512514) isotope compositions. The combined isotope and chemical data suggest the derivation of the western Turkish volcanics from variable mixtures of melts generated in two different mantle regions. The calc-alkaline volcanics were essentially derived from the continental lithospheric or shallow asthenospheric mantle which was contaminated with upper crustal material during earlier subduction events. The generation of the alkaline volcanics was controlled by melts derived from relatively deep, isotopically depleted mantle regions. Most of the volcanics were subjected to contamination at crustal levels, through the operation of an assimilation–fractional crystallization (AFC) process. The nature of contaminant changed from upper crustal in the calc-alkaline to lower crustal in the alkaline volcanics, accompanying the overall decrease in the amount of contamination from about 50% down to about 10%, and broadly paralleling the transition from compressional to extensional tectonics in the region.

scholarly journals Nd-Hf isotope geochemistry and lithogeochemistry of the Rambler Rhyolite, Ming VMS deposit, Baie Verte Peninsula, Newfoundland: evidence for slab melting and implications for VMS localization

2021 ◽  
Author(s):  
S J Piercey ◽  
J -L Pilote
Keyword(s):  
Rare Earth ◽  
Trace Element ◽  
Isotope Geochemistry ◽  
Primitive Mantle ◽  
Isotopic Data ◽  
Depleted Mantle ◽  
Element Enrichment ◽  
Felsic Volcanic ◽  
Magmatic History ◽  
Felsic Rocks

New high precision lithogeochemistry and Nd and Hf isotopic data were collected on felsic rocks of the Rambler Rhyolite formation from the Ming volcanogenic massive sulphide (VMS) deposit, Baie Verte Peninsula, Newfoundland. The Rambler Rhyolite formation consists of intermediate to felsic volcanic and volcaniclastic rocks with U-shaped primitive mantle normalized trace element patterns with negative Nb anomalies, light rare earth element-enrichment (high La/Sm), and distinctively positive Zr and Hf anomalies relative to surrounding middle rare earth elements (high Zr-Hf/Sm). The Rambler Rhyolite samples have epsilon-Ndt = -2.5 to -1.1 and epsilon-Hft = +3.6 to +6.6; depleted mantle model ages are TDM(Nd) = 1.3-1.5 Ga and TDM(Hf) = 0.9-1.1Ga. The decoupling of the Nd and Hf isotopic data is reflected in epsilon-Hft isotopic data that lies above the mantle array in epsilon-Ndt -epsilon-Hft space with positive ?epsilon-Hft values (+2.3 to +6.2). These Hf-Nd isotopic attributes, and high Zr-Hf/Sm and U-shaped trace element patterns, are consistent with these rocks having formed as slab melts, consistent with previous studies. The association of these slab melt rocks with Au-bearing VMS mineralization, and their FI-FII trace element signatures that are similar to rhyolites in Au-rich VMS deposits in other belts (e.g., Abitibi), suggests that assuming that FI-FII felsic rocks are less prospective is invalid and highlights the importance of having an integrated, full understanding of the tectono-magmatic history of a given belt before assigning whether or not it is prospective for VMS mineralization.

Fluids composition in the mantle beneath the Eastern Transylvanian Basin inferred from mineral chemistry and noble gases in fluid inclusions of ultramafic xenoliths

2021 ◽  
Author(s):  
Andrea Luca Rizzo ◽  
Barbara Faccini ◽  
Costanza Bonadiman ◽  
Theodoros Ntaflos ◽  
Ioan Seghedi ◽  
...  
Keyword(s):  
Fluid Inclusions ◽  
Noble Gases ◽  
Mineral Chemistry ◽  
Mantle Xenoliths ◽  
Alkaline Magmatism ◽  
Volcanic Area ◽  
Crustal Material ◽  
Calc Alkaline ◽  
Depleted Mantle ◽  
Magmatic Gases

<p>The investigation of noble gases (He, Ne, Ar) and CO<sub>2</sub> in fluid inclusions (FI) of mantle-derived rocks from the Sub Continental Lithospheric Mantle (SCLM) is crucial for constraining its geochemical features and evolution as well as the volatiles cycle, and for better evaluating the information arising from the study and monitoring of volcanic and geothermal gases. Eastern Transylvanian Basin in Romania is one of the places in Central-Eastern Europe where mantle xenoliths are brought to the surface by alkaline magmatism, offering the opportunity for applying the above-mentioned approach. Moreover, this locality is one of the few places on Earth where alkaline eruptions occurred contemporaneously with calc-alkaline activity, thus being a promising area for the investigation of subduction influence on the magma sources and volatiles composition.</p><p>In this work, we studied petrography, mineral chemistry and noble gases in FI of mantle xenoliths found in Perşani Mts. alkaline volcanic products. Our findings reveal that the local mantle recorded two main events. The first was a pervasive, complete re-fertilization of a previously depleted mantle by a calc-alkaline subduction-related melt, causing the formation of very fertile, amphibole-bearing lithotypes. Fluids involved in this process and trapped in olivine, opx and cpx, show <sup>4</sup>He/<sup>40</sup>Ar* ratios up to 1.2 and among the most radiogenic <sup>3</sup>He/<sup>4</sup>He values of the European mantle (5.8 ± 0.2 Ra), reflecting the recycling of crustal material in the local lithosphere. The second event is related to a later interaction with an alkaline metasomatic agent similar to the host basalts, that caused slight LREE enrichment in pyroxenes and crystallization of disseminated amphiboles, with FI showing <sup>4</sup>He/<sup>40</sup>Ar* and <sup>3</sup>He/<sup>4</sup>He values up to 2.5 and 6.6 Ra, respectively, more typical of magmatic fluids.</p><p>Although volcanic activity in the Perşani Mts. is now extinct, strong CO<sub>2</sub> degassing (8.7 × 10<sup>3</sup> t/y) in the neighbouring Ciomadul volcanic area may indicate that magma is still present at depth (Kis et al., 2017; Laumonier et al., 2019). The gas manifestations present from Ciomadul area are the closest to the outcrops containing mantle xenoliths for comparison of the noble gas composition in FI. <sup>3</sup>He/<sup>4</sup>He values from Stinky Cave (Puturosul), Doboşeni and Balvanyos are up to 3.2, 4.4 and 4.5 Ra, respectively, indicating the presence of a cooling magma (Vaselli et al., 2002 and references therein). In the same area and more recently, Kis et al. (2019) measured <sup>3</sup>He/<sup>4</sup>He ratios up to 3.1 Ra, arguing that these values indicate a mantle lithosphere strongly contaminated by subduction-related fluids and post-metasomatic ingrowth of radiogenic <sup>4</sup>He. Our findings consider more likely that magmatic gases from Ciomadul volcano are not representative of the local mantle but are being released from a cooling and aging magma that resides within the crust. Alternatively, crustal fluids contaminate magmatic gases while they are rising to the surface.</p><p> </p><p>Kis et al. (2017). Journal of Volcanology and Geothermal Research 341, 119–130.</p><p>Kis et al. (2019) Geochem. Geophys. Geosyst. 20, 3019-3043.</p><p>Laumonier et al. (2019) Earth and Planetary Science Letters, 521, 79-90.</p><p>Vaselli et al. (2002) Chemical Geology 182, 637–654.</p>

Petrographic, Geochemical and Isotopic (Sr–Nd–Pb–Os) Study of Plio-Quaternary Volcanics and the Tertiary Basement in the Jorullo-Tacámbaro Area, Michoacán-Guanajuato Volcanic Field, Mexico

2019 ◽  
Vol 60 (12) ◽  
pp. 2317-2338 ◽  
Author(s):  
Marie-Noëlle Guilbaud ◽  
Claus Siebe ◽  
Christine Rasoazanamparany ◽  
Elisabeth Widom ◽  
Sergio Salinas ◽  
...  
Keyword(s):  
Trace Element ◽  
Crustal Contamination ◽  
Volcanic Belt ◽  
Volcanic Field ◽  
Calc Alkaline ◽  
Trace Element Pattern ◽  
Alkaline Rocks ◽  
Rock Types ◽  
Oceanic Sediments ◽  
Element Pattern

Abstract The origin of the large diversity of rock types erupted along the subduction-related Trans-Mexican Volcanic Belt (TMVB) remains highly debated. In particular, several hypotheses have been proposed to explain the contemporary eruption of calc-alkaline and alkaline magmas along the belt. The Michoacán-Guanajuato Volcanic Field (MGVF) is an atypical, vast region of monogenetic activity located in the western-central part of the TMVB. Here we present new petrographic, geochemical, and isotopic (Sr–Nd–Pb–Os) data on recent volcanics in the Jorullo-Tacámbaro area that is the closest to the oceanic trench. TMVB-related volcanics in this area are Plio-Quaternary (<5 Ma) and mainly form a calc-alkaline series from basalts to dacites, with rare (<5 vol. %) alkaline rocks that range from trachybasalts to trachydacites, and transitional samples. Crystal textures are consistent with rapid crystallization at shallow depth and processes of mixing of similar magma batches (magma recharge). All of the samples exhibit an arc-type trace element pattern. Alkaline and transitional magmas have higher Na2O and K2O, lower Al2O3, and higher concentrations in incompatible elements (e.g. Sr, K, Ba, Th, Ce, P) compared to calc-alkaline rocks. Calc-alkaline rocks are similar isotopically to transitional and alkaline samples, except for a few low 87Sr/86Sr samples. Sr, Nd and Pb isotopes do not correlate with MgO or 187Os/188Os, indicating that they were not significantly influenced by crustal contamination. Isotopic and trace-element systematics suggest that the Tacámbaro magmas are produced by melting of a mantle wedge fluxed by fluids derived from a mixture of subducted sediments and altered oceanic crust. Alkaline and transitional magmas can be derived from a lower degree of partial melting of a similar source to that of the calc-alkaline rocks, whereas the few low 87Sr/86Sr calc-alkaline rocks require a lower proportion of fluid derived from oceanic sediments and crust. Volcanism at the trenchward edge of the MGVF was thus driven purely by subduction during the last 5 Ma, hence discarding slab rollback in this sector of the TMVB.

scholarly journals Petrology of the Doda Granites, Jammu Lesser Himalaya, India

1996 ◽  
Vol 14 ◽  
Author(s):  
B. L. Dhar ◽  
A. K. Raina ◽  
B. K. Fotedar ◽  
R. Singh
Keyword(s):  
Partial Melting ◽  
Granitic Rocks ◽  
Crustal Material ◽  
Lesser Himalaya ◽  
Calc Alkaline ◽  
Nw Himalaya ◽  
Jammu And Kashmir ◽  
Lower Crustal ◽  
Highly Evolved

Granitic rocks in the Doda district of Jammu and Kashmir State, NW Himalaya are exposed at eight places. They are named as Dramman, Piparan, Kaplas, Khol Dedni, Chinta, Bhala, Kai Nala, and Nagin Dhar Granites. They occur in the form of irregular bodies of varying dimensions. These granites are mostly leucocratic, two-mica, porphyritic to aplitic, massive and highly jointed with crude foliation in some cases. The contact with the Older Metamorphics is sharp and thermal aureole is absent. These granites are monzo- to syeno-granitic in composition with peraluminous, S-type (equivalent to ilmenite series) and calc-alkaline affinity. These intrusive bodies are emplaced within the Older Metamorphics under tectonic influences at later stages of metamorphism. They have formed from highly evolved anatectic granites derived by partial melting of lower crustal material with diapiric situations. These processes had been operative at a temperature of 600-700°C at a depth of 20-30 km under 5 Kb Pressure. The emplacement of these granites is suggested to be due to transient dilation where the diapir is enhanced by sheeting mechanism.

A geochemical study of the Crown Formation and Bird Member lavas of the Mesoarchaean Witwatersrand Supergroup, South Africa

2021 ◽  
Author(s):  
F. Humbert ◽  
A. Hofmann ◽  
M. de Kock ◽  
A. Agangi ◽  
Y-M. Chou ◽  
...  
Keyword(s):  
South Africa ◽  
Trace Element ◽  
Incompatible Trace Element ◽  
Major And Trace Elements ◽  
Primitive Mantle ◽  
Geodynamic Setting ◽  
Crustal Material ◽  
Geochemical Composition ◽  
Crown Formation ◽  
The Difference

Abstract: The ca. 2.97 to 2.80 Ga Witwatersrand Supergroup, South Africa, represents the oldest intracontinental sedimentary basin of the Kaapvaal craton. Two volcanic units occur in this supergroup: the widespread Crown Formation lavas in the marine shale-dominated West Rand Group and the more geographically restricted Bird Member lavas, intercalated with fluvial to fluvio-deltaic sandstone and conglomerate of the Central Rand Group. These units remain poorly studied as they are rarely exposed and generally deeply weathered when cropping out. We report whole-rock major and trace elements, Hf and Nd-isotope whole-rock analyses of the lavas from core samples drilled in the south of the Witwatersrand basin and underground samples from the Evander Goldfield in the northeast. In the studied areas, both the Crown Formation and Bird Member are composed of two units of lava separated by sandstone. Whereas all the Crown Formation samples show a similar geochemical composition, the upper and lower volcanic units of the Bird Member present clear differences. However, the primitive mantle-normalized incompatible trace element concentrations of all Crown Formation and Bird Member samples show variously enriched patterns and marked negative Nb and Ta anomalies relative to Th and La. Despite the convergent geodynamic setting of the Witwatersrand Supergroup suggested by the literature, the Crown Formation and Bird Member are probably not related to subduction-related magmatism but more to decompression melting. Overall, the combined trace element and Sm-Nd isotopic data indicate melts from slightly to moderately depleted sources that were variably contaminated with crustal material. Greater contamination, followed by differentiation in different magma chambers, can explain the difference between the two signatures of the Bird Member. Finally, despite previous proposals for stratigraphically correlating the Witwatersrand Supergroup to the Mozaan Group of the Pongola Supergroup, their volcanic units are overall geochemically distinct.

scholarly journals Petrogenesis of Magnesian High-K Granitoids From Bitkine (Centrechad Massif): Major and Trace Elements Constraints

2020 ◽  
Vol 1 (5) ◽  
Author(s):  
Mbaihoudou Diontar ◽  
Jean Claude Doumnang ◽  
Maurice Kwékam ◽  
Zagalo Al-hadj Hamid ◽  
Armand Kagou Dongmo ◽  
...  
Keyword(s):  
Trace Elements ◽  
Trace Element ◽  
Fractional Crystallization ◽  
Major And Trace Elements ◽  
Trace Element Data ◽  
Calc Alkaline ◽  
Element Data ◽  
High K ◽  
Microgranular Enclaves ◽  
Mantle Magma

Major and trace element data were used to constrain the nature and origin of the Bitkine gabbro-diorite magma.The gabbro-diorites of Bitkine within the Guéra Massif, and associated microgranular enclaves consist of plagioclase, k-feldspar, clinopyroxene, amphibole, biotite and quartz. Gabbro-diorites and enclaves are basic to intermediate rocks. They are high-K magnesian calc-alkaline with shoshonite affinity. ΣREE range from 132 to 436 ppm in gabbro-diorites, while they are from 134 to 207 ppm in enclaves. LREE are weakly enriched compared to HREE (La/Yb)N = (12.23 -41.40) and (6.20-31.86) respectively in gabbro-diorites and enclaves. These rocks show a weak negative anomaly in europium (Eu/Eu* = 0.78-1.07). They are rich in Ba and Sr, and show negative anomalies in Nb, Ta and Ti. The Nb/Ta, Rb/Cs and Ba/Nb ratios of the Bitkine gabbro-diorites and their enclaves indicate that they are derived from mantle magma modified by subducted fluids. This magma during its evolution by fractional crystallization was contaminated by crustal materials.

TRACE ELEMENT CHEMISTRY OF EMERALDS

2018 ◽  
Author(s):  
Casey Beaudoin ◽  
◽  
G. Nelson Eby
Keyword(s):  
Trace Element ◽  
Trace Element Chemistry ◽  
Element Chemistry
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