Mafic enclaves in the Wilson Ridge Pluton, northwestern Arizona: Implications for the generation of a calc-alkaline intermediate pluton in an extensional environment

The Qingshanbao complex, part of the uranium metallogenic belt of the Longshou-Qilian mountains, is located in the center of the Longshou Mountain next to the Jiling complex that hosts a number of U deposits. However, little research has been conducted in this area. In order to investigate the origin and formation of mafic enclaves observed in the Qingshanbao body and the implications for magmatic-tectonic dynamics, we systematically studied the mineralogy, petrography, and geochemistry of these enclaves. Our results showed that the enclaves contain plagioclase enwrapped by early dark minerals. These enclaves also showed round quartz crystals and acicular apatite in association with the plagioclase. Electron probe analyses showed that the plagioclase in the host rocks (such as K-feldspar granite, adamellite, granodiorite, etc.) show normal zoning, while the plagioclase in the mafic enclaves has a discontinuous rim composition and shows instances of reverse zoning. Major elemental geochemistry revealed that the mafic enclaves belong to the calc-alkaline rocks that are rich in titanium, iron, aluminum, and depleted in silica, while the host rocks are calc-alkaline to alkaline rocks with enrichment in silica. On Harker diagrams, SiO2 contents are negatively correlated with all major oxides but K2O. Both the mafic enclaves and host rock are rich in large ion lithophile elements such as Rb and K, as well as elements such as La, Nd, and Sm, and relatively poor in high field strength elements such as Nb, Ta, P, Ti, and U. Element ratios of Nb/La, Rb/Sr, and Nb/Ta indicate that the mafic enclaves were formed by the mixing of mafic and felsic magma. In terms of rare earth elements, both the mafic enclaves and the host rock show right-inclined trends with similar weak to medium degrees of negative Eu anomaly and with no obvious Ce anomaly. Zircon LA-ICP-MS (Laser ablation inductively coupled plasma mass spectrometry) U-Pb concordant ages of the mafic enclaves and host rock were determined to be 431.8 5.2 Ma (MSWD (mean standard weighted deviation)= 1.5, n = 14) and 432.8 4.2 Ma (MSWD = 1.7, n = 16), respectively, consistent with that for the zircon U-Pb ages of the granite and medium-coarse grained K-feldspar granites of the Qingshanbao complex. The estimated ages coincide with the timing of the late Caledonian collision of the Alashan Block. This comprehensive analysis allowed us to conclude that the mafic enclaves in the Qingshanbao complex were formed by the mixing of crust-mantle magma with mantle-derived magma due to underplating, which caused partial melting of the ancient basement crust during the collisional orogenesis between the Alashan Block and Qilian rock mass in the early Silurian Period.

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Evolution of mafic enclaves and their host calc-alkaline granite, South Sinai, Egypt

Arabian Journal of Geosciences ◽

10.1007/s12517-021-09085-w ◽

2021 ◽

Vol 14 (24) ◽

Author(s):

N. I. Abd El Ghaffar

Keyword(s):

Calc Alkaline ◽

Alkaline Granite ◽

Mafic Enclaves ◽

South Sinai

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Igneous banding, schlieren and mafic enclaves in calc-alkaline granites: The Budduso pluton (Sardinia)

Lithos ◽

10.1016/j.lithos.2007.12.004 ◽

2008 ◽

Vol 104 (1-4) ◽

pp. 147-163 ◽

Cited By ~ 42

Author(s):

P. Barbey ◽

D. Gasquet ◽

C. Pin ◽

A.L. Bourgeix

Keyword(s):

Calc Alkaline ◽

Mafic Enclaves

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Chemical Evolution of Calc-alkaline Magmas during the Ascent through Continental Crust: Constraints from Methana, Aegean Arc

Journal of Petrology ◽

10.1093/petrology/egaa036 ◽

2020 ◽

Vol 61 (3) ◽

Cited By ~ 2

Author(s):

Milena V Schoenhofen ◽

Karsten M Haase ◽

Christoph Beier ◽

Dominic Woelki ◽

Marcel Regelous

Keyword(s):

Trace Element ◽

Continental Crust ◽

Fractional Crystallization ◽

Magma Mixing ◽

Basaltic Magma ◽

High Water ◽

Calc Alkaline ◽

Mafic Enclaves ◽

Aegean Arc ◽

Mineral Compositions

Abstract Quaternary calc-alkaline andesitic to dacitic lavas effusively erupted on top of about 30 km thick accreted continental crust at Methana peninsula in the western Aegean arc. We present new data of major and trace element concentrations as well as of Sr–Nd–Pb isotope ratios along with mineral compositions of Methana lavas and their mafic enclaves. The enclaves imply a parental basaltic magma and fractional crystallization processes with relatively little crustal assimilation in the deep part of the Methana magma system. The composition of amphibole in some mafic enclaves and lavas indicates deeper crystallization at ∼25 km depth close to the Moho compared with the evolved lavas that formed at <15 km depth. The presence of amphibole and low Ca contents in olivine suggest high water contents of ∼4 wt% in the primitive magmas at Methana. The compositions of andesitic and dacitic lavas reflect fractional crystallization, assimilation of sedimentary material, and magma mixing in the upper 15 km of the crust. The Methana magmas have fO2 of FMQ + 1 to FMQ + 2 (where FMQ is the fayalite–magnetite–quartz buffer) at temperatures of 1200 to 750 °C and the fO2 does not vary systematically from mafic to felsic compositions, suggesting that the mantle wedge was oxidized by sediment subduction. Amphibole is an important fractionating phase in the more evolved Methana magmas and causes significant changes in incompatible element ratios. Although xenocrysts and mineral compositions indicate magma mixing, the major and trace element variation implies only limited mixing between dacitic and basaltic melts.

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ROCHAS GRANULÍTICAS DA SUÍTE CAPARAÓ NA REGIÃO DO PICO DA BANDEIRA: EMBASAMENTO ORIENTAL DO ORÓGENO ARAÇUAÍ

Revista Geonomos ◽

10.18285/geonomos.v19i2.42 ◽

2013 ◽

Author(s):

Tiago Amâncio Novo ◽

Carlos Maurício Noce ◽

Antônio Carlos Pedrosa-Soares ◽

Gustavo Antonio Pereira Batista

Keyword(s):

Minas Gerais ◽

Calc Alkaline ◽

Mountain Ridge ◽

Espírito Santo ◽

Mafic Enclaves ◽

High K ◽

Espirito Santo ◽

Araçuaí Orogen ◽

Light Rare Earth Elements ◽

Western Limb

O Pico da Bandeira é o terceiro cume mais alto do Brasil com 2891,98 m de altitude. Localiza-se na Serra do Caparaó, divisa dos estados de Minas Gerais e Espírito Santo. Esta serra tem sido esculpida essencialmente sobre gnaisses e migmatitos de alto grau, ortoderivados, de composição diorítica a granítica, com encraves máficos, da Suíte Caparaó. Estruturalmente, a Serra do Caparaó configura uma lasca tectônica moldada em antiformal de proporções quilométricas, assimétrico, apertado, aproximadamente orientado segundo NNE-SSW, com o flanco oeste parcialmente invertido e charneira marcada por intensa migmatização. As poucas amostras analisadas sugerem rochas cálcio-alcalinas de médio a alto-K, um pouco enriquecidas em terras raras leves em relação a rochas similares do Complexo Juiz de Fora. A Suíte Caparaó, de idade riaciana (ca. 2,19 Ga), pode ser correlacionada ao Complexo Juiz de Fora e constitui uma porção do embasamento sudeste do Orógeno Araçuaí.Palavras-chave: Granulito, Suíte Caparaó, Orógeno Araçuaí ABSTRACT: GRANULITIC ROCKS FROM THE CAPARAÓ SUITE IN THE PICO DA BANDEIRA REGION: EASTERN BASEMENT OF THE ARAÇUAÍ OROGEN. In Brazil, the third highest mountain peak, with 2891.98 m high, is called Pico da Bandeira. It is located at Caparaó mountain ridge, along the boundary between Minas Gerais and Espírito Santo states. This ridge has been shaped on the orthoderived, dioritic to granitic, granulitic gneisses and migmatites with mafic enclaves of the Caparaó Suite. The regional structure of the Caparaó ridge is a folded thrust slice, forming a huge antiformal, asymmetric, tight fold roughly oriented to NNE-SSW, with the western limb partially inverted and the hinge marked by intense migmatization. The few analysed samples suggest medium to high-K calc-alkaline signatures, slightly enriched in light rare earth elements in relation to similar rocks of the Juiz de Fora Complex. The Caparaó Suite, Rhyacian in age (ca. 2.19 Ga), can be correlated to the Juiz de Fora Complex and forms part of the southeastern basement of the Araçuaí orogen.Keywords: Granulite, Caparaó Suite, Araçuaí orogen

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Petrology and Geochemical Characteristic of Granitoids From Guéra Massif in the Central Part of Chad: An Example of Mixing Magmas

Earth Science Research ◽

10.5539/esr.v9n2p66 ◽

2020 ◽

Vol 9 (2) ◽

pp. 66

Author(s):

Diontar Mbaihoudou ◽

Kwékam Maurice ◽

Fozing Eric Martial ◽

Kagou Dongmo Armand ◽

Tcheumenak Kouémo Jules

Keyword(s):

Biotite Granite ◽

Continental Lithosphere ◽

Calc Alkaline ◽

Mafic Enclaves ◽

Pan African ◽

High K ◽

Major Process ◽

Alkaline Feldspar ◽

Petrology And Geochemistry ◽

Shoshonitic Series

The granitoids of Guéra Massif are composed of biotite-granite, amphibole-biotite granite and gabbro-diorite and commonly contain micro granular mafic enclaves which vary from monzogabbro to syenite composition. They are metaluminous, high-K calc-alkaline to shoshonitic series. Gabbro-diorite rocks are magnesian while amphibole-biotite granites are magnesian to ferroan, and biotite granites are ferroan. They are enriched in LREEs relative to HREE and display negative anomalies in Nb, Ta and Ti. Fields relationships, petrology and geochemistry indicate that mixing and mingling processes could be more relevant for the genesis of granitoids associated to fractional crystallization. Thus, the presence of mafic enclaves of gabbro-diorite composition in the granites, the resumption of alkaline feldspar xenocrystals in the gabbro-diorites, as well as the linear correlation between the granites and the gabbro-diorites and the intermediate position of the mafic enclaves between the two formations, enable us to propose magmatic mixing as the major process that presided over the evolution of the Guéra granitoids. The delamination of the continental lithosphere during the post-collisional phase of the Pan-African orogeny would have caused the partial melting of the subduction-modofied mantle and lower continental crust and thus produced the magmas of the Guéra granitoids.

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Calc-alkaline plutonism along the Pacific rim of southern Alaska

Open-File Report ◽

10.3133/ofr79953 ◽

1979 ◽

Cited By ~ 5

Author(s):

Travis Hudson

Keyword(s):

Pacific Rim ◽

Calc Alkaline ◽

The Pacific

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Laramide to Miocene syn-extensional plutonism in the Puerta del Sol area, central Sonora, Mexico

Revista Mexicana de Ciencias Geológicas ◽

10.22201/cgeo.20072902e.2017.1.401 ◽

2017 ◽

Vol 34 (1) ◽

pp. 45 ◽

Cited By ~ 5

Author(s):

Elizard González-Becuar ◽

Efrén Pérez-Segura ◽

Ricardo Vega-Granillo ◽

Luigi Solari ◽

Carlos Manuel González-León ◽

...

Keyword(s):

Metamorphic Core Complex ◽

Primitive Mantle ◽

Isotopic Ratios ◽

Magmatic Evolution ◽

Calc Alkaline ◽

Core Complex ◽

High K ◽

Sierra Madre ◽

Plutonic Rocks ◽

Metamorphic Core

Plutonic rocks of the Puerta del Sol area, in central Sonora, represent the extension to the south of the El Jaralito batholith, and are part of the footwall of the Sierra Mazatán metamorphic core complex, whose low-angle detachment fault bounds the outcrops of plutonic rocks to the west. Plutons in the area record the magmatic evolution of the Laramide arc and the Oligo-Miocene syn-extensional plutonism in Sonora. The basement of the area is composed by the ca. 1.68 Ga El Palofierral orthogneiss that is part of the Caborca block. The Laramide plutons include the El Gato diorite (71.29 ± 0.45 Ma, U-Pb), the El Pajarito granite (67.9 ± 0.43 Ma, U-Pb), and the Puerta del Sol granodiorite (49.1 ± 0.46 Ma, U-Pb). The younger El Oquimonis granite (41.78 ± 0.32 Ma, U-Pb) is considered part of the scarce magmatism that in Sonora records a transition to the Sierra Madre Occidental magmatic event. The syn-extensional plutons are the El Garambullo gabbro (19.83 ± 0.18 Ma, U-Pb) and the Las Mayitas granodiorite (19.2 ± 1.2 Ma, K-Ar). A migmatitic event that affected the El Palofierral orthogneiss, El Gato diorite, and El Pajarito granite between ca. 68 and 59 Ma might be related to the emplacement of the El Pajarito granite. The plutons are metaluminous to slightly peraluminous, with the exception of El Oquimonis granite, which is a peraluminous two-mica, garnet-bearing granite. They are mostly high-K calc-alkaline with nearly uniform chondrite-normalized REE and primitive-mantle normalized multielemental patterns that are characteristic of continental margin arcs and resemble patterns reported for other Laramide granites of Sonora. The Laramide and syn-extensional plutons also have Sr, Nd and Pb isotopic ratios that plot within the fields reported for Laramide granites emplaced in the Caborca terrane in northwestern and central Sonora. Nevertheless, and despite their geochemical affinity to continental magmatic arcs, the El Garambullo gabbro and Las Mayitas granodiorite are syn-extensional plutons that were emplaced at ca. 20 Ma during development of the Sierra Mazatán metamorphic core complex. The 40Ar/39Ar and K-Ar ages obtained for the El Palofierral orthogneiss, the Puerta del Sol granodiorite, the El Oquimonis granite, and the El Garambullo gabbro range from 26.3 ± 0.6 to 17.4 ± 1.0 Ma and are considered cooling ages associated with the exhumation of the metamorphic core complex.

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