Supplemental Material: Early Cenozoic partial melting of meta-sedimentary rocks of the eastern Gangdese arc, southern Tibet, and its contribution to syn-collisional magmatism

10.1130/gsab.s.14241947.v1 ◽

2021 ◽

Author(s):

Yuan-Yuan Jiang ◽

et al.

Keyword(s):

Trace Element ◽

Partial Melting ◽

Sedimentary Rocks ◽

Hf Isotope ◽

Chemical Compositions ◽

Trace Element Data ◽

Southern Tibet ◽

Magmatic Arc ◽

Isotope Data ◽

Early Cenozoic

The chemical compositions of minerals from the paragneisses (Tables S1–S3), the zircon and monazite age and trace element data of the paragneisses and leucosome (Tables S4–S5), and the zircon Lu-Hf isotope data of the paragneisses and leucosome (Table S6) from the eastern Gangdese magmatic arc.

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Early Cenozoic partial melting of meta-sedimentary rocks of the eastern Gangdese arc, southern Tibet, and its contribution to syn-collisional magmatism

Geological Society of America Bulletin ◽

10.1130/b35763.1 ◽

2021 ◽

Author(s):

Yuan-Yuan Jiang ◽

Ze-Ming Zhang ◽

Richard M. Palin ◽

Hui-Xia Ding ◽

Xuan-Xue Mo

Keyword(s):

Partial Melting ◽

Lower Crust ◽

Sedimentary Rocks ◽

Late Carboniferous ◽

Southern Tibet ◽

Magmatic Arc ◽

Magmatic Rocks ◽

Deep Crust ◽

Juvenile Crust ◽

Early Cenozoic

Continental magmatic arcs are characterized by the accretion of voluminous mantle-derived magmatic rocks and the growth of juvenile crust. However, significant volumes of meta-sedimentary rocks occur in the middle and lower arc crust, and the contributions of these rocks to the evolution of arc crust remain unclear. In this paper, we conduct a systematic study of petrology, geochronology, and geochemistry of migmatitic paragneisses from the eastern Gangdese magmatic arc, southern Tibet. The results show that the paragneisses were derived from late Carboniferous greywacke, and underwent an early Cenozoic (69−41 Ma) upper amphibolite-facies metamorphism and partial melting at pressure-temperature conditions of ∼11 kbar and ∼740 °C, and generated granitic melts with enriched Hf isotopic compositions (anatectic zircon εHf(t) = −10.57 to +0.78). Combined with the existing results, we conclude that the widely distributed meta-sedimentary rocks in the eastern Gangdese arc deep crust have the same protolith ages of late Carboniferous, and record northwestward-decreasing metamorphic conditions. We consider that the deeply buried sedimentary rocks resulted in the compositional change of juvenile lower crust from mafic to felsic and the formation of syn-collisional S-type granitoids. The mixing of melts derived from mantle, juvenile lower crust, and ancient crustal materials resulted in the isotopic enrichment of the syn-collisional arc-type magmatic rocks of the Gangdese arc. We suggest that crustal shortening and underthrusting, and the accretion of mantle-derived magma during the Indo-Asian collision transported the supracrustal rocks to the deep crust of the Gangdese arc.

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Rare-earth and other trace element data bearing on the origin of Archaean granitic rocks from Yellowknife, Northwest Territories

Canadian Journal of Earth Sciences ◽

10.1139/e79-071 ◽

1979 ◽

Vol 16 (4) ◽

pp. 809-815 ◽

Cited By ~ 13

Author(s):

S. A. Drury

Keyword(s):

Rare Earth ◽

Trace Element ◽

Partial Melting ◽

Northwest Territories ◽

Granitic Rocks ◽

Trace Element Data ◽

Sr Isotope ◽

Isotope Data ◽

Element Data ◽

Ree Patterns

Trace element data, including rare-earth elements, for six granitic rocks and two metasediments from the Archaean granite–greenstone terrain of Yellowknife, Northwest Territories are presented. Three granodiorites from the synkinematic Western and South-east plutons show similar Rb, Sr, Th, Rb/Sr, and K/Rb to many high level granodiorites, but are enriched in Ba. Their rare-earth element (REE) patterns show enrichment of light REE relative to heavy REE, and lack Eu anomalies. These features, together with Sr isotope data, are compatible with their origin by partial melting of mantle depth garnet-bearing basaltic source rocks, and little if any detectable fractionation of the rising magma. Potassic granites from post-kinematic plutons, such as the Prosperous Lake granite, are enriched in Th, depleted in Sr and Eu, and have very high Rb/Sr ratios and low K/Rb ratios. Their REE patterns, except for Eu, are very similar to those of metasediments which they intrude. These features, together with Sr isotope data, suggest that high degrees of partial melting of metasediments, leaving a plagioclase-rich residue, are the most likely origin for the post-kinematic granites. The REE patterns of the Archaean metasediments, in particular their high CeN/YbN ratios, suggest that they contain a high proportion of material derived from earlier sialic crust, and that local metavolcanic rocks are not clearly reflected in the composition of the stratigraphically younger metasediments.

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Supplemental Material: The Mesozoic magmatic, metamorphic, and tectonic evolution of the eastern Gangdese magmatic arc, southern Tibet

10.1130/gsab.s.16548213 ◽

2021 ◽

Author(s):

Zeming Zhang

Keyword(s):

Trace Element ◽

Late Cretaceous ◽

Tectonic Evolution ◽

Chemical Compositions ◽

Isotopic Data ◽

Southern Tibet ◽

Magmatic Arc ◽

Magmatic Rocks

Table S1: Major features of the reported Jurassic magmatic rocks of the eastern Gangdese arc; Table S2: Zircon U-Pb dating and trace element (in ppm) data of the studied Jurassic magmatic rocks of the eastern Gangdese arc; Table S3: Zircon Hf isotopic data of the studied Jurassic magmatic rocks of the eastern Gangdese arc; Table S4: Whole-rock chemical compositions of the studied Jurassic magmatic rocks of the eastern Gangdese arc; Table S5: Whole-rock chemical compositions of the Mesozoic magmatic rocks of the eastern Gangdese arc; Table S6: Whole-rock SiO2 and Cu concentrations of the Late Cretaceous magmatic rocks of the eastern Gangdese arc.

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Spotted structures in gneiss and veins from Broken Hill, New South Wales, Australia

Mineralogical Magazine ◽

10.1180/minmag.1980.043.330.13 ◽

1980 ◽

Vol 43 (330) ◽

pp. 779-787

Author(s):

Bryan E Chenhall ◽

Evan R. Phillips ◽

R. Gradwell

Keyword(s):

Trace Element ◽

Partial Melting ◽

Prolate Spheroid ◽

Matrix Phase ◽

Chemical Compositions ◽

Trace Element Data ◽

Element Data ◽

Broken Hill ◽

Vein Formation ◽

The Matrix

SynopsisSpotted eye-like structures, made up of densely packed biotite ‘pupils’ mantled by quartz and feld-spar, constitute about 10% by volume of a high-grade quartzofeldspathic gneiss located on the road to Purnamoota Homestead about 10 km north of Broken Hill. These spotted structures have an uneven distribution within rocks exposed at this locality. In some parts of the outcrop they tend to be closely spaced (fig. 1), whereas elsewhere they are less abundant and the spotted gneiss merges into an essentially homogeneous gneiss composed of quartz (34%. by volume), plagioclase (24%), Kfeldspar (17%), biotite (20%), and garnet, muscovite, and opaques (5%). This homogeneous gneiss is believed to have developed into a ‘matrix’ gneiss phase holding the ‘eyes’ which have a felsic mantle to mafic clot ratio of 4:1.The whole eye-like structure appears to be a distorted prolate spheroid with its axis set close to the foliation plane of the gneiss. The internal biotite clot forms another prolate spheroid with its axis inclined at approximately 70° to that of the enveloping quartz-feldspar mantle. Although most of the eyes are isolated within the matrix, some are linked to hold three or four biotite aggregates (fig. S1) and rarely a vein-like patch which contains some ten or more partly linked spots of biotite may be found. In addition to the biotite, xenoblasts of almandine occur within some of the eye-like structures.Whole-rock chemical analyses (including both major oxides and trace elements) show that the homogeneous gneiss and the spotted gneiss are very similar. The most notable feature of the geochemistry of the spotted rocks is the close chemical correspondence between the matrix and the whole eyes. Moreover, the compositions of corresponding minerals in these phases are very similar. For example, plagioclase is consistently about An35–40, the biotites are all very iron-rich (Fe/(Fe + Mg) ≈ 0.87) with compositions near siderophyllite, and K-feldspar has the composition Or94Ab6.It has been suggested that the biotite spots formed by alteration of garnet probably during a retrograde metamorphic event. However, studies of the microstructure of the biotite and garnet in the spotted gneiss show that biotite of the spots does not replace garnet. Furthermore, the chemical similarity between the spots and the matrix is best explained by an isochemical rearrangement of components of the matrix phase to form the eyes. Thus, a more likely origin is best related to the displacement of matter along chemical potential gradients possibly induced by deformation in the rock system—a process described by the term metamorphic differentiation.Veins in the Purnamoota Road gneiss are of two main contrasting types—regularly-disposed veinlets which are composed almost entirely of K-feldspar and quartz, and irregularly shaped discontinuous trondhjemitoid variants rich in biotite spots and carrying rare garnet porphyroblasts. The field relationship between these two main types of veins is difficult to discern. In some parts of the out-crop the veins occur adjacent to one another and locally appear to merge. Veins with modal (and chemical) compositions intermediate between the spotted and the K-feldspar-rich veins have also been recorded from the outcrop.Despite a wide whole-rock chemical variation, the minerals in all the veins are similar chemically and compare closely with corresponding minerals in the host gneiss. One exception may be the plagioclase in veins rich in K-feldspar where normative calculations indicate a composition near An14.Interpretation of the trace element data counts against the veins having formed by partial melting and the variable K-feldspar contents place both main vein types well away from ternary minima in the system Q-Ab-Or. Calculations based on the compositions of co-existing biotite and garnet in the host quartzofeldspathic gneiss and in associated prograde pelitic schists indicate an equilibrium temperature of 650° ± 50 °C at pressures between 3 and 4 kilobars. This fact, together with trace element data and the calcic nature of the plagioclase in the homogeneous gneiss and the matrix phase, places some doubt on the suggestion that partial melting has played a signficant role in the genesis of the veins.Although mechanisms of vein formation such as igneous injection or metasomatism are considered as other alternatives for vein formation, we suggest that metamorphic segregation (as proposed for the origin of the spots in the gneiss) will also account for the development of the veins.

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Supplemental Material: The Mesozoic magmatic, metamorphic, and tectonic evolution of the eastern Gangdese magmatic arc, southern Tibet

10.1130/gsab.s.16548213.v1 ◽

2021 ◽

Author(s):

Zeming Zhang

Keyword(s):

Trace Element ◽

Late Cretaceous ◽

Tectonic Evolution ◽

Chemical Compositions ◽

Isotopic Data ◽

Southern Tibet ◽

Magmatic Arc ◽

Magmatic Rocks

Table S1: Major features of the reported Jurassic magmatic rocks of the eastern Gangdese arc; Table S2: Zircon U-Pb dating and trace element (in ppm) data of the studied Jurassic magmatic rocks of the eastern Gangdese arc; Table S3: Zircon Hf isotopic data of the studied Jurassic magmatic rocks of the eastern Gangdese arc; Table S4: Whole-rock chemical compositions of the studied Jurassic magmatic rocks of the eastern Gangdese arc; Table S5: Whole-rock chemical compositions of the Mesozoic magmatic rocks of the eastern Gangdese arc; Table S6: Whole-rock SiO2 and Cu concentrations of the Late Cretaceous magmatic rocks of the eastern Gangdese arc.

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U-Pb geochronology of Paraná volcanics combined with trace element geochemistry of the zircon crystals and zircon Hf isotope data

Journal of South American Earth Sciences ◽

10.1016/j.jsames.2018.11.026 ◽

2019 ◽

Vol 89 ◽

pp. 219-226 ◽

Cited By ~ 6

Author(s):

Léo A. Hartmann ◽

Sérgio B. Baggio ◽

Matheus P. Brückmann ◽

Daniel B. Knijnik ◽

Cristiano Lana ◽

...

Keyword(s):

Trace Element ◽

Hf Isotope ◽

Trace Element Geochemistry ◽

Element Geochemistry ◽

Isotope Data ◽

Zircon Hf Isotope

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Geochemical evidence for the emplacement of the Whin Sill complex of northern England

Geological Magazine ◽

10.1017/s0016756800031836 ◽

1985 ◽

Vol 122 (4) ◽

pp. 389-396 ◽

Cited By ~ 11

Author(s):

R. S. Thorpe ◽

R. Macdonald

Keyword(s):

Trace Elements ◽

Trace Element ◽

Partial Melting ◽

Sedimentary Rocks ◽

Crustal Contamination ◽

Mantle Peridotite ◽

Chemical Characteristics ◽

Heterogeneous Mantle ◽

Magma Pulses ◽

Significant Chemical

AbstractThe Whin Sill comprises a major quartz tholeiite sill of late Carboniferous age underlying an area of c. 5000 km2 and with a volume of c. 200 km3, associated with contemporaneous dykes emplaced within Carboniferous sedimentary rocks in northeast England. New trace element analyses of chilled margins, sill interiors and dykes indicate that the Whin Sill complex magmas show significant chemical variations in terms of the relatively stable trace elements Th, Ce, Y, Zr, Nb and Ni. These data indicate that the complex was fed by a large number of compositionally distinct magma pulses, and that certain of the dykes may have formed feeder channels for the sill. The chemical characteristics of the sill and dyke samples are consistent with derivation by extensive polybaric fractional crystallization of olivine tholeiite magma derived by partial melting of compositionally heterogeneous mantle peridotite and/or crustal contamination of mantle-derived magmas.

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