scholarly journals Coupled magmatic and host rock processes during the initiation of the Tuolumne Intrusive Complex, Sierra Nevada, California, USA: A transition from ephemeral sheets to long-lived, active magma mushes

2021 ◽  
Author(s):  
Valbone Memeti ◽  
Scott R. Paterson ◽  
Roland Mundil
Keyword(s):  
Mass Spectrometry ◽  
Sierra Nevada ◽  
Inductively Coupled Plasma ◽  
Isotope Geochemistry ◽  
Magma Mixing ◽  
Volcanic Eruptions ◽  
Ionization Mass ◽  
Intrusive Complex ◽  
Magma Pulses ◽  
Host Rocks

The initiation of pluton formation is rarely preserved as the rock record is typically overprinted by younger intruding pulses. An exception is the 80 km2 Kuna Crest lobe, which marks the initiation of the 95−85 Ma, 1100 km2 Tuolumne Intrusive Complex in the Sierra Nevada, California, USA. We present a detailed map of the lithologies and structure of the Kuna Crest lobe, associated sheeted complex and satellite plutons, and their host rocks, using chemical abrasion−isotope dilution−thermal ionization mass spectrometry and laser ablation−inductively coupled plasma−mass spectrometry U-Pb zircon geochronology, element and isotope geochemistry, and Al-in-hornblende thermobarometry to conclude the following: (a) The 94.91 ± 0.53 Ma to 92.75 ± 0.11 Ma Kuna Crest lobe and its marginal sheeted complex preserved the oldest intrusive pulses and most mantle-like compositions of the entire Tuolumne Intrusive Complex. (b) Emplacement began with magma wedging of low volume magma pulses resulting in a sheeted complex that is compositionally heterogeneous at outcrop scales, but isotopically homogeneous. (c) These early magmas established a pre-heated pathway within just a few hundreds of thousands of years that gave way to the formation of the ∼1.5 million-year-long active, compositionally more homogeneous but isotopically more heterogeneous magma mush across the Kuna Crest lobe. The host rocks and previously intruded magma were displaced largely vertically through downward flow. (d) The melt-interconnected mush zone in the lobe allowed for magma mixing and crystal-liquid separation at the emplacement level. We interpret this lobe to represent an upper- to mid-crustal, vertical magma transfer zone that likely fed shallower plutons and potentially volcanic eruptions. We propose a filter pressing mechanism driven by vertical magma transport through the lobe resulting in margin-parallel fabrics, plagioclase-rich crystal cumulates, inward draining and upward loss (of up to 40%) of interstitial melts. Some inward drained melts hybridized with later intruding Half Dome magmas at the transition to the main Tuolumne Intrusive Complex. Some of the lobe magmas, including fractionated melts, drained laterally into the strain shadow of the lobe to form the satellite plutons, further contributing to cumulate formation in the lobe. This study documents that within only a few hundreds of thousands of years, arc magma plumbing systems are capable of establishing a focused magma pathway to build up to increasingly larger magma bodies that are capable of undergoing magma differentiation and feeding shallower plutons and volcanic eruptions.

Stitching together the Ungava Orogen, northern Quebec: geochronological (TIMS and ICP–MS) and geochemical constraints on late magmatic events

1995 ◽  
Vol 32 (12) ◽  
pp. 2115-2127 ◽  
Author(s):  
J. M. Dunphy ◽  
J. N. Ludden ◽  
R. R. Parrish
Keyword(s):  
Mass Spectrometry ◽  
Continental Crust ◽  
Inductively Coupled Plasma ◽  
Ionization Mass ◽  
Inductively Coupled ◽  
High K ◽  
Icp Ms ◽  
Plasma Mass Spectrometry ◽  
High Concentrations ◽  
Host Rocks

Late magmatic activity in the Ungava Orogen of northern Quebec is manifest as granitic dykes and small, rare plutons that crosscut all tectono-stratigraphic elements of the orogen. Conventional U–Pb geochronology (thermal ionization mass spectrometry (TIMS)) on one particularly important pluton that cuts all these domains (the Lac Duquet monzogranite) indicates its age of emplacement at 1742.2 ± 1.3 Ma. This undeformed and nonmetamorphosed pluton postdates the youngest structures in the orogen (D4 folds), thereby constraining the timing of the latest deformation to >1742 Ma. Laser ablation inductively coupled plasma–mass spectrometry (ICP–MS) on zircons from the same sample identified a large range in 207Pb/206Pb ages of inherited grains from 1.7 to 3.2 Ga, corresponding to the ages of the host rocks for the pluton. This high-K peraluminous monzogranite pluton contains moderate to high concentrations of large ion lithophile elements and fractionated and enriched light rare earth elements, similar in composition to the surrounding continental crust and to other crustally derived granites. Initial 87Sr/86Sr values of 0.7040–0.7051 and εNd ranging from −4.4 to −9.7 indicate incorporation of a significant amount of older material in the petrogenesis of the pluton. It is proposed that anatexis of the surrounding continental crust due to structural thickening during the waning stages of the Ungava orogeny resulted in the generation of the Lac Duquet pluton and was the source for its inherited zircons.

Field relationships, petrology, age, and tectonic setting of the Late Cambrian–Ordovician West Barneys River Plutonic Suite, southern Antigonish Highlands, Nova Scotia, Canada

2013 ◽  
Vol 50 (7) ◽  
pp. 727-745 ◽  
Author(s):  
D.B. Archibald ◽  
S.M. Barr ◽  
J.B. Murphy ◽  
C.E. White ◽  
T.G. MacHattie ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Inductively Coupled Plasma ◽  
Magma Mixing ◽  
Tectonic Setting ◽  
Alkali Feldspar ◽  
Chemical Compositions ◽  
Ionization Mass ◽  
The West ◽  
Inductively Coupled ◽  
Plasma Mass Spectrometry

The West Barneys River Plutonic Suite consists of gabbro, syenite-monzonite, alkali-feldspar syenite to quartz alkali-feldspar syenite, and alkali-feldspar granite outcropping in an area of ∼100 km2 in the southern Antigonish Highlands. Magma mixing and mingling textures indicate a comagmatic relationship between some of the mafic and intermediate–felsic lithologies. However, nine U–Pb (zircon) ages, three by thermal ionization mass spectrometry (TIMS) and six by laser-ablation – inductively coupled plasma – mass spectrometry (LA–ICP–MS), from the West Barneys River suite and the lithologically similar Cape Porcupine Complex located 60 km to the east range from ca. 495 to 460 Ma, indicating that emplacement occurred over a significant span of time. Intermediate to felsic rocks consist mainly of perthitic K-feldspar and variable amounts of quartz; interstitial granophyre is present in some samples, consistent with shallow emplacement. Mafic phases are Fe-rich amphibole and clinopyroxene, and in some units, fayalite. Intermediate and felsic samples have chemical characteristics of within-plate ferroan A-type granitoid rocks. Gabbroic rocks consist of plagioclase (oligoclase–labradorite) and augite/diopside with less abundant orthopyroxene, olivine, biotite, and ilmenite/magnetite. Their chemical compositions are transitional from tholeiitic to alkalic and characteristic of continental within-plate mafic rocks. The εNd values are similar in gabbroic, syenitic, and granitic samples, ranging between 0.9 and 4.9, consistent with a co-genetic origin for the mafic and intermediate/felsic components of the suite, and derivation from Avalonian subcontinental lithospheric mantle in an extensional environment.

An Archean Porphyry-Type Gold Deposit: The Côté Gold Au(-Cu) Deposit, Swayze Greenstone Belt, Superior Province, Ontario, Canada

2020 ◽  
Author(s):  
Laura R. Katz ◽  
Daniel J. Kontak ◽  
Benoît Dubé ◽  
Vicki McNicoll ◽  
Robert Creaser ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Gold Deposit ◽  
Greenstone Belt ◽  
Inductively Coupled Plasma ◽  
Gold Mineralization ◽  
Spatial Association ◽  
Ionization Mass ◽  
Low Grade ◽  
Intrusive Complex ◽  
Al Composite

Abstract The Archean low-grade, large-tonnage Côté Gold Au(-Cu) deposit is the first large gold deposit discovered in the Swayze greenstone belt, Ontario, Canada. The deposit is hosted by the Chester Intrusive Complex, a low-Al composite, subvolcanic intrusion composed of tonalite, quartz diorite, and diorite that was previously constrained to ca. 2741 to 2739 Ma (U-Pb zircon). Presented here is the first detailed study of the mineralization and related alteration, along with the relative and absolute age (U-Pb, Re-Os) constraints on gold mineralization. The earliest hydrothermal stage is represented by rare Au-bearing amphibole-rich veins and breccias. The main ore stage consists of biotite-rich alteration centered on an Au(-Cu)–bearing magmatic-hydrothermal biotite breccia body with spatially related disseminated biotite and veins of both sheeted and stockwork type. Extensive fracture-controlled and replacement-style Au ± Cu-bearing muscovite alteration overprints biotite-altered rocks in the core of the deposit. Barren fracture-controlled and disseminated epidote alteration is localized to the north of the deposit and above the magmatic-hydrothermal biotite breccia. Late, texturally destructive albite alteration overprints the mineralized hydrothermal alteration in the deposit core. U-Pb isotope dilution-thermal ionization mass spectrometry and laser ablation-inductively coupled plasma-mass spectrometry ages for hydrothermal titanite from amphibole (2745 ± 3 Ma) and albite (2737.5 +2.2/–1.8, 2745 ± 9, and 2736 ± 7 Ma) alteration assemblages constrain hydrothermal activity to ca. 2740 Ma. The timing of gold and sulfide mineralization is also constrained by two Re-Os molybdenite ages of 2736.1 ± 11.4 (biotite alteration) and 2746.8 ± 11.4 Ma (muscovite alteration). These new ages overlap with the ca. 2741 to 2739 Ma magmatism for the Chester Intrusive Complex, thereby suggesting a synintrusion, magmatic-hydrothermal origin for the gold mineralization and related alteration. This is significant, as it represents a new gold metallogenic event in the Abitibi subprovince, for which regional importance remains to be defined. Considering the spatial association of the deposit with a dioritic intrusion and the temporal overlap of igneous activity with alteration (i.e., amphibole, biotite, sericite) and mineralization (i.e., breccias, veins, disseminations), the deposit is interpreted as an Archean magmatic-hydrothermal ore system sharing analogies with Phanerozoic Au-Cu porphyry deposits. It suggests that Archean porphyry-type deposits can form in low-Al composite intrusions, which are known to host Cu-Mo-Au breccia, vein, and disseminated mineralization and underlie temporally and genetically related felsic to intermediate volcanic rocks that host volcanogenic massive sulfide deposits.

scholarly journals Magma Mixing Genesis of the Mafic Enclaves in the Qingshanbao Complex of Longshou Mountain, China: Evidence from Petrology, Geochemistry, and Zircon Chronology

Minerals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 195 ◽  
Author(s):  
Wenheng Liu ◽  
Xiaodong Liu ◽  
Jiayong Pan ◽  
Kaixing Wang ◽  
Gang Wang ◽  
...  
Keyword(s):  
Host Rock ◽  
Inductively Coupled Plasma ◽  
Magma Mixing ◽  
Coarse Grained ◽  
Calc Alkaline ◽  
Quartz Crystals ◽  
Alkaline Rocks ◽  
Mafic Enclaves ◽  
Normal Zoning ◽  
Host Rocks

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.

Contact Metamorphic and Metasomatic Processes at the Kharaelakh Intrusion, Oktyabrsk Deposit, Norilsk-Talnakh Ore District: Application of LA-ICP-MS Dating of Perovskite, Apatite, Garnet, and Titanite

2020 ◽  
Vol 115 (6) ◽  
pp. 1213-1226 ◽  
Author(s):  
Alexander E. Marfin ◽  
Alexei V. Ivanov ◽  
Vadim S. Kamenetsky ◽  
Adam Abersteiner ◽  
Tamara Yu. Yakich ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Inductively Coupled Plasma ◽  
Metamorphic Rocks ◽  
Complete Agreement ◽  
Ionization Mass ◽  
Pb Isotope ◽  
Inductively Coupled ◽  
Prolonged Duration ◽  
Plasma Mass Spectrometry ◽  
Ore District

Abstract The Norilsk-Talnakh ore district in the northwestern Siberian platform contains globally unique reserves of Cu-Ni-sulfides with Pt and, especially, Pd. The Oktyabrsk deposit, which is one of the largest in the district, is spatially and genetically associated with the Kharaelakh mafic-ultramafic intrusion and its exceptionally large metamorphic and metasomatic aureoles. In this study, we employed in situ laser ablation-inductively coupled plasma-mass spectrometry U-Pb isotope dating of apatite, titanite, garnet, and perovskite that cocrystallize with disseminated sulfides within the aureole of metasomatic and contact metamorphic rocks. The calculated isotopic ages for apatite (257.3 ± 4.5 and 248.9 ± 5.1 Ma), titanite (248.6 ± 6.8 and 249.1 ± 2.9 Ma), garnet (260.0 ± 11.0 Ma), and perovskite (247.3 ± 8.2 Ma), though with large uncertainties, indicate that sulfide mineralization within metasomatic and contact-metamorphic rocks is coeval with the emplacement of the Kharaelakh intrusion. These isotopic dates are in complete agreement with the published isotope dilution-thermal ionization mass spectrometry U-Pb zircon ages for the Norilsk intrusions and, at the same time, notably older than available Re-Os isochron ages of sulfides. The latter ages have been long interpreted as evidence for a prolonged duration of magmatic ore-forming processes; however, our data narrow their life span. Trace elements in titanite and garnet allow distinguishing late- and postmagmatic grains, which show indistinguishable U-Pb isotope ages.

Geology and U–Pb geochronology of the Neoarchean Snare River terrane: tracking evolving tectonic regimes and crustal growth mechanisms

2005 ◽  
Vol 42 (6) ◽  
pp. 895-934 ◽  
Author(s):  
Venessa Bennett ◽  
Valerie A Jackson ◽  
Toby Rivers ◽  
Carolyn Relf ◽  
Pat Horan ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Detrital Zircon ◽  
Inductively Coupled Plasma ◽  
Granulite Facies ◽  
Crustal Thickening ◽  
Ionization Mass ◽  
Granulite Facies Metamorphism ◽  
Zircon Crystallization ◽  
Facies Metamorphism ◽  
Turbidite Sedimentation

U–Pb zircon crystallization ages determined by isotope dilution – thermal ionization mass spectrometry (ID–TIMS) and laser ablation microprobe – inductively coupled plasma – mass spectrometry (LAM–ICP–MS) for 13 intrusive units in the Neoarchean Snare River terrane (SRT) provide tight constraints on the timing of crust formation and orogenic evolution. Seven metaluminous plutons were emplaced over ~80 Ma from ca. 2674 to 2589 Ma, whereas six peraluminous bodies were emplaced in a ~15 Ma interval from ca. 2598 to 2585 Ma. A detrital zircon study yielded an age spectrum with peaks correlative with known magmatic events in the Slave Province, with the ca. 2635 Ma age of the youngest detrital zircon population providing a maximum estimate for the onset of sedimentation. This age contrasts with evidence for pre-2635 Ma sedimentation elsewhere in the SRT, indicating that sedimentation was protracted and diachronous. Evolution of the SRT can be subdivided into four stages: (i) 2674–2635 Ma — formation of a metaluminous protoarc in a tonalite–trondhjemite–granodiorite (TTG) – granite–greenstone tectonic regime (TR1) and coeval with early turbidite sedimentation; (ii) 2635–2608 Ma — continued turbidite sedimentation, D1/M1 juxtaposition of turbidites and protoarc lithologies prior to ~2608 Ma, and metaluminous granitoid plutonism; (iii) 2608–2597 Ma — onset of TR2, collision of Snare protoarc with Central Slave Basement Complex, D2/M2 crustal thickening and mid-crustal granulite-facies metamorphism, sychronous with metaluminous and peraluminous plutonism; and (iv) 2597–2586 Ma — orogenic collapse, D3/M3 mid-crustal uplift, granulite-facies metamorphism, and waning metaluminous and peraluminous plutonism. The distribution of igneous rocks yields an "orogenic stratigraphy" with an older upper crust underlain by a younger synorogenic mid-crust. These data can be used to provide constraints for the interpretation of the Slave – Northern Cordillera Lithospheric Evolution (SNORCLE) Lithoprobe transect.

Free soil colloids and colloidal building units of soil aggregates

2020 ◽  
Author(s):  
Ni Tang ◽  
Nina Siebers ◽  
Erwin Klumpp
Keyword(s):  
Mass Spectrometry ◽  
Organic Matter ◽  
Organic Carbon ◽  
Inductively Coupled Plasma ◽  
Soil Aggregates ◽  
Size Fraction ◽  
Ionization Mass ◽  
Soil Matrix ◽  
Size Fractions ◽  
20 Nm

<p>Nanosized mineral particles and organic matter (<100 nm) ,as well as their associations, belong to the most important ingredients for the formation of the soil aggregate structure being a hierarchically organized system. Colloids (< 220 nm) including nanoparticles can be occluded as primary building units of soil aggregates. Nevertheless, a large proportion of these colloids is mobile and presents in the solution phase (as “free”) within the soil matrix. However, the differences between “free” and occluded colloids remain unclear.</p><p>Here, both occluded and free colloids were isolated from soil samples of an arable field with different clay contents (19% and 34%) using wet sieving and centrifugation. The release of occluded colloids from soil macroaggregates (>250 µm) was carried out with ultrasonic treatment at 1000 J mL<sup>-1</sup>. The free and occluded colloidal fractions were then characterized for their size-resolved elemental composition using flow field-flow fractionation inductively coupled plasma mass spectrometry and organic carbon detector (FFF-ICP-MS/OCD). In addition, selected samples were also subjected to transmission electron microscopy as well as pyrolysis field ionization mass spectrometry (Py-FIMS).</p><p>Both, free and occluded colloids were composed of three size fractions: nanoparticles <20 nm, medium-sized nanoparticles (20 nm–60 nm), and, fine colloids (60 nm–220 nm). The fine colloid fraction was the dominant size fraction in both free and occluded colloids, which mainly consist of organic carbon, Al, Si, and Fe, probably present as phyllosilicates and associations of Fe- and Al- (hydr)oxides and organic matter. However, the organic matter contents for all three size fractions were higher for the occluded colloids than for the free ones. The role of OM concentration and composition in these colloids will be discussed in the paper.</p>

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