High-magnesian andesite from Mount Shasta: A product of magma mixing and contamination, not a primitive mantle melt

Streck, Martin J.; Leeman, William P.; Chesley, John T.

doi:10.1130/g23286a.1

Cited by 418 publications

(151 citation statements)

References 27 publications

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“…Finally, there is a clear compositional gap between high-Mg andesites (SiO 2 = 54-60 wt.%) and dacites (SiO 2 = 67-71 wt.%) (Figs. 5 and 6), which is inconsistent with the continuous compositional trend implied by AFC, FC or magma mixing processes (Castillo et al, 1999;Macpherson et al, 2006;Streck et al, 2007).…”

Section: Petrogenesismentioning

confidence: 43%

“…First, the Hohxil dacites, including a sample with the lowest LOI or H 2 O + CO 2 content (indicating the least alteration), exhibits initial 87 Sr/ 86 Sr isotopic ratios slightly lower than those of the high-Mg andesites (Appendix 8l and Fig. 9), which is inconsistent with AFC or magma mixing models (Castillo et al, 1999;Streck et al, 2007). A positive correlation between Th/Nb and εNd(t) values (Fig.…”

Section: Petrogenesismentioning

confidence: 70%

“…Second, geochemical disequilibrium (e.g., low Mg # core and high Mg # rim) during the crystallization of augites in the Hohxil high-Mg andesites (Appendix 1e, f; Figs. 3-4), not only argues against low-Mg # crustal material assimilation, but also is inconsistent with the compositions (e.g., low Mg # rim and high Mg # interior) of zoned augites from magma mixing-derived high-Mg andesites (Streck et al, 2007). Third, PGE (e.g., Ir) contents do not decrease with increasing Th contents (an indicator of the degree of fractionation) (Fig.…”

Section: Petrogenesismentioning

confidence: 94%

“…8a), indicating that variations in their PGE content are not related to sulfide fractional crystallization (Setiabudi et al, 2007). Fourth, the Hohxil high-Mg andesite-adakitic rock suites are not associated with contemporary basaltic rocks that would correspond to the required mafic end member in AFC, FC and magma mixing models (e.g., Castillo et al, 1999;Macpherson et al, 2006;Streck et al, 2007). Finally, there is a clear compositional gap between high-Mg andesites (SiO 2 = 54-60 wt.%) and dacites (SiO 2 = 67-71 wt.%) (Figs.…”

Section: Petrogenesismentioning

confidence: 97%

“…5-7). There are different models accounting for the petrogenesis of such highMg andesite-adakitic rock suites, including assimilation fractional crystallization (AFC) or fractional crystallization (FC) from parental basaltic magmas (Castillo et al, 1999;Macpherson et al, 2006), magma mixing between felsic and basaltic magmas (e.g., Streck et al, 2007), and interaction between melts and mantle (e.g., Gao et al, 2004; (Rapp et al, 1999(Rapp et al, , 2003, and references therein). The fields for delaminated lower crust, subducted oceanic crust, and thickened lower crust-derived adakitic rocks are after Wang et al (2006a, b).…”

Section: Petrogenesismentioning

confidence: 99%

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Late Triassic high-Mg andesite/dacite suites from northern Hohxil, North Tibet: Geochronology, geochemical characteristics, petrogenetic processes and tectonic implications

Wang

Chung

et al. 2011

Lithos

102

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Section: Petrogenesismentioning

confidence: 43%

Section: Petrogenesismentioning

confidence: 70%

Section: Petrogenesismentioning

confidence: 94%

Section: Petrogenesismentioning

confidence: 97%

Section: Petrogenesismentioning

confidence: 99%

See 3 more Smart Citations

Late Triassic high-Mg andesite/dacite suites from northern Hohxil, North Tibet: Geochronology, geochemical characteristics, petrogenetic processes and tectonic implications

Wang

Chung

et al. 2011

Lithos

102

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Diverse magmatic effects of subducting a hot slab in SW Japan: Results from forward modeling

Kimura

Gill

Kunikiyo³

et al. 2014

Geochem Geophys Geosyst

211

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In response to the subduction of the young Shikoku Basin of the Philippine Sea Plate, arc magmas erupted in SW Japan throughout the late Cenozoic. Many magma types are present including ocean island basalt (OIB), shoshonite (SHO), arc-type alkali basalt (AB), typical subalkalic arc basalt (SAB), high-Mg andesite (HMA), and adakite (ADK). OIB erupted since the Japan Sea back-arc basin opened, whereas subsequent arc magmas accompanied subduction of the Shikoku Basin. However, there the origin of the magmas in relation to hot subduction is debated. Using new major and trace element and Sr-Nd-Pb-Hf isotope analyses of 324 lava samples from seven Quaternary volcanoes, we investigated the genetic conditions of the magma suites using a geochemical mass balance model, Arc Basalt Simulator version 4 (ABS4), that uses these data to solve for the parameters such as pressure/temperature of slab dehydration/melting and slab flux fraction, pressure, and temperature of mantle melting. The calculations suggest that those magmas originated from slab melts that induced flux melting of mantle peridotite. The suites differ mostly in the mass fraction of slab-melt flux, increasing from SHO through AB, SAB, HMA, to ADK. The pressure and temperature of mantle melting decreases in the same order. The suites differ secondarily in the ratio of altered oceanic crust to sediment in the source of the slab melt. The atypical suites associated with hot subduction result from unusually large mass fractions of slab melt and unusually cool mantle temperatures.

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Eocene adakitic porphyries in the central‐northern Qiangtang Block, central Tibet: Partial melting of thickened lower crust and implications for initial surface uplifting of the plateau

Wang

Wyman

et al. 2017

JGR Solid Earth

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The time and mechanism of crustal thickening and initial surface uplift of the Tibetan Plateau remain highly controversial. Here we report on zircon U‐Pb age, and mineral, element, and Sr‐Nd isotope composition data for Eocene adakitic porphyries in the Laorite Co area of central‐northern Qiangtang Block, central Tibet. Laser ablation‐inductively coupled plasma‐mass spectrometry zircon U‐Pb age dating shows that the porphyries were generated at 42–41 Ma. All samples display adakitic geochemical characteristics, such as high SiO2 and Al2O3, and low Y and Yb contents, and high Sr/Y and La/Yb ratios with positive Sr and negligible Eu anomalies and Nb‐Ta depletion. They also have low magnesium number (Mg #) (16–45) and high K2O (4.0–4.6 wt %) values, as well as high (87Sr/86Sr)i (0.7076–0.7080) and low εNd(t) (−5.9 to −4.4) values. These adakitic rocks were most probably generated by partial melting of thickened lower crust in the stability field of garnet, amphibole, and rutile but with relatively minor plagioclase. Moreover, such a crustal thickening process beneath this block likely occurred no later than the middle Eocene and was most probably caused by the southward subduction of the Songpan‐Ganzi Block in the early Cenozoic. In addition, the occurrences of exposed adakitic porphyries unambiguously indicate that exhumation process occurred after their formation. Thus, these ~42 Ma adakitic porphyries indicate the occurrence of significant exhumation since 42 Ma. Integrated with the thermochronological and paleoelevation data, we suggest that the initial surface uplift of the Qiangtang Block, triggered by crustal thickening, was underway by the middle Eocene (~42 Ma).

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High-magnesian andesite from Mount Shasta: A product of magma mixing and contamination, not a primitive mantle melt

Cited by 418 publications

References 27 publications

Late Triassic high-Mg andesite/dacite suites from northern Hohxil, North Tibet: Geochronology, geochemical characteristics, petrogenetic processes and tectonic implications

Late Triassic high-Mg andesite/dacite suites from northern Hohxil, North Tibet: Geochronology, geochemical characteristics, petrogenetic processes and tectonic implications

Diverse magmatic effects of subducting a hot slab in SW Japan: Results from forward modeling

Eocene adakitic porphyries in the central‐northern Qiangtang Block, central Tibet: Partial melting of thickened lower crust and implications for initial surface uplifting of the plateau

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