The mare basalt magma source region and mare basalt magma genesis

1982 ◽  
Vol 87 (S01) ◽  
pp. A37 ◽  
Author(s):  
Alan B. Binder
Keyword(s):  
Source Region ◽  
Magma Source ◽  
Basalt Magma ◽  
Magma Genesis ◽  
Mare Basalt

scholarly journals Differentiating between Inherited and Autocrystic Zircon in Granitoids

2020 ◽  
Vol 61 (8) ◽  
Author(s):  
Hugo K H Olierook ◽  
Christopher L Kirkland ◽  
Kristoffer Szilas ◽  
Julie A Hollis ◽  
Nicholas J Gardiner ◽  
...  
Keyword(s):  
Trace Element ◽  
Source Region ◽  
Wall Rock ◽  
Magma Source ◽  
Trace Element Data ◽  
Element Data ◽  
Age Constraints ◽  
Erroneous Interpretation ◽  
Zircon Fraction

Abstract Inherited zircon, crystals that did not form in situ from their host magma but were incorporated from either the source region or assimilated from the wall-rock, is common but can be difficult to identify. Age, chemical and/or textural dissimilarity to the youngest zircon fraction are the primary mechanisms of distinguishing such grains. However, in Zr-undersaturated magmas, the entire zircon population may be inherited and, if not identifiable via textural constraints, can lead to erroneous interpretation of magmatic crystallization age and magma source. Here, we present detailed field mapping of cross-cutting relationships, whole-rock geochemistry and zircon textural, U–Pb and trace element data for trondhjemite, granodiorite and granite from two localities in a complex Archean gneiss terrane in SW Greenland, which reveal cryptic zircon inheritance. Zircon textural, U–Pb and trace element data demonstrate that, in both localities, trondhjemite is the oldest rock (3011 ± 5 Ma, 2σ), which is intruded by granodiorite (2978 ± 4 Ma, 2σ). However, granite intrusions, constrained by cross-cutting relationships as the youngest component, contain only inherited zircon derived from trondhjemite and granodiorite based on ages and trace element concentrations. Without age constraints on the older two lithologies, it would be tempting to consider the youngest zircon fraction as recording crystallization of the granite but this would be erroneous. Furthermore, whole-rock geochemistry indicates that the granite contains only 6 µg g–1 Zr, extremely low for a granitoid with ∼77 wt% SiO2. Such low Zr concentration explains the lack of autocrystic zircon in the granite. We expand on a differentiation tool that uses Th/U ratios in zircon versus that in the whole-rock to aid in the identification of inherited zircon. This work emphasizes the need for field observations, geochemistry, grain characterization, and precise geochronology to accurately determine igneous crystallization ages and differentiate between inherited and autocrystic zircon.

Geochemistry, zircon ages and whole-rock Nd isotopic systematics for Palaeoproterozoic A-type granitoids in the northern part of the Delhi belt, Rajasthan, NW India: implications for late Palaeoproterozoic crustal evolution of the Aravalli craton

2006 ◽  
Vol 144 (2) ◽  
pp. 361-378 ◽  
Author(s):  
PARAMPREET KAUR ◽  
NAVEEN CHAUDHRI ◽  
INGRID RACZEK ◽  
ALFRED KRÖNER ◽  
ALBRECHT W. HOFMANN
Keyword(s):  
Source Region ◽  
Magma Source ◽  
Crustal Evolution ◽  
Nd Isotope ◽  
Tectonic Environment ◽  
Granulite Metamorphism ◽  
Extensional Tectonic ◽  
Aravalli Craton ◽  
Isotope Systematics

Determination of zircon ages as well as geochemical and Sm–Nd isotope systematics of granitoids in the Khetri Copper Belt of the Aravalli mountains, NW India, constrain the late Palaeoproterozoic crustal evolution of the Aravalli craton. The plutons are typical A-type within-plate granites, derived from melts generated in an extensional tectonic environment. They display REE and multi-element patterns characterized by steep LREE-enriched and almost flat HREE profiles and distinct negative anomalies for Sr, P and Ti. Initial εNd values range from −1.3 to −6.2 and correspond to crustal sources with mean crustal residence ages of 2.5 to 2.1 Ga. A lower mafic crustal anatectic origin is envisaged for these granitoids, and the heterogeneous εNd(t) values are inferred to have been acquired from the magma source region. Zircon Pb–Pb evaporation and U–Pb ages indicate widespread rift-related A-type magmatism at 1711–1660 Ma in the northern Delhi belt and also suggest a discrete older magmatic event at around 1800 Ma. The emplacement ages of the compositionally distinct A-type granitoid plutons, and virtually coeval granulite metamorphism and exhumation in another segment of the Aravalli mountains, further signify that part of the Aravalli crust evolved during a widespread extensional event in late Palaeoproterozoic time.

scholarly journals On the source region of the lunar mare basalt

2001 ◽  
Vol 106 (E7) ◽  
pp. 14691-14700 ◽  
Author(s):  
Arkani-Hamed Jafar ◽  
Alison Pentecost
Keyword(s):  
Source Region ◽  
Mare Basalt ◽  
Lunar Mare

Zircon U–Pb geochronology, Hf isotope composition, and petrochemical characteristics of Paleocene granitoids in the western Gangdese Belt, Tibet

2021 ◽  
Author(s):  
J.Q. Lin ◽  
F. Ding ◽  
C.H. Chen ◽  
T. Shen
Keyword(s):  
Isotope Composition ◽  
Source Region ◽  
Hf Isotope ◽  
Magma Source ◽  
Calc Alkaline ◽  
Peraluminous Granite ◽  
High K ◽  
Stable Isotopic ◽  
Tethys Ocean ◽  
The Impact

Abstract ––The research team studied the petrology, whole-rock geochemistry, zircon U–Pb age, and stable isotopic characteristics of the Rongguo Longba and Garongcuo granites of the Nuocang area to better understand the impact of Neo-Tethys ocean subduction and In-dia–Eurasia continental collision on Paleocene tectonomagmatic processes along the southern margin of the Gangdese Belt. The Rongguo Longba granite and Garongcuo granite porphyry formed at 61.86 and 62.17 Ma, respectively. The Nuocang granitoids are characterized by (1) high SiO2, NaO2, and Al2O3 contents and low FeOT, MgO, and TiO2 contents; (2) LREE and LILE enrichment and HREE and HFSE (Nb, P, and Ti) depletion; and (3) obvious negative Eu anomalies. These features indicate that the Nuocang granites are of the high-K calc-alkaline and peraluminous granite types. Furthermore, their zircon Hf isotope characteristics suggest that the magma source region has an ancient crystalline basement. The basaltic andesitic crystal tuff is the product of garnet–peridotite partial melting and crust contamination from rising magma emplacement.

Boron and lithium isotopic compositions as provenance indicators of Cu-bearing tourmalines

2010 ◽  
Vol 74 (2) ◽  
pp. 241-255 ◽  
Author(s):  
B. M. Shabaga ◽  
M. Fayek ◽  
F. C. Hawthorne
Keyword(s):  
Late Stage ◽  
Isotope Fractionation ◽  
Large Range ◽  
Source Region ◽  
Magma Ascent ◽  
Magma Source ◽  
B Values ◽  
Granite Pegmatite ◽  
Isotopic Compositions ◽  
Li Isotope

AbstractThe Li and B isotopic compositions of gem-quality Cu-bearing tourmalines were used (1) to distinguish among Paraiba tourmalines from Brazil and Cu-bearing tourmalines from Nigeria and Mozambique; and (2) to identify the likely source of Li and B for these gem-quality tourmalines. The δ11B values of tourmaline from Paraiba, Brazil, range from –42.4‰ to –32.9‰, whereas the δ11B values of Cu-bearing tourmaline from Nigeria and Mozambique range from –30.5‰ to –22.7‰ and –20.8‰ to –19.1‰ respectively. Tourmalines from each locality have relatively homogeneous δ11B values and display no overlap. There is slight overlap between δ7Li values of Paraiba tourmaline (+24.5‰ to +32.9‰) and Cu-bearing tourmaline from Nigeria (+32.4‰ to +35.4‰), and δ7Li values of Cu-bearing tourmaline from Nigeria and Mozambique (+31.5‰ to +46.8‰). Nevertheless, Cu-bearing tourmalines from each locality can be fingerprinted using a combination of their δ11B and δ7Li values. The very small δ11B values are consistent with a non-marine evaporite source, and are among the smallest reported for magmatic systems, expanding the global range of B isotopicc omposition for tourmaline by 12‰. The corresponding large δ7Li values are among the largest reported, although they are less diagnostic of the source of the Li. The large δ7Li values in conjunction with the small δ11B values suggest a non-marine evaporite or brine as a source for Li and B, either as constituent(s) of the magma source region or, by assimilation during magma ascent. The large range in δ11B and δ7Li values suggests that B and Li isotope fractionation occurred during magmatic degassing and late-stage magmatic-hydrothermal evolution of the granite-pegmatite system.

MESOZOIC Mo MINERALIZATION IN NORTHEASTERN CHINA DID NOT REQUIRE REGIONAL-SCALE PRE-ENRICHMENT

2021 ◽  
Author(s):  
Qihai Shu ◽  
Massimo Chiaradia
Keyword(s):  
Lower Crust ◽  
Large Scale ◽  
Source Region ◽  
Regional Scale ◽  
Northeastern China ◽  
Magma Source ◽  
Oceanic Plate ◽  
Ne China ◽  
Cretaceous Deposits ◽  
Regional Compression

Abstract Northeastern China is one of the richest Mo-mineralized regions in China, with 95 Mesozoic Mo-bearing deposits and a total metal resource of >12.2 Mt Mo. The reasons behind the large-scale Mesozoic Mo mineralization in NE China remain unclear, and whether or not there was any regional-scale pre-enrichment of the source region (e.g., a Mo-rich lower crust) is still a matter of debate. In this study, whole-rock Nd and zircon Hf isotope compositions of the intrusions related to the Mo mineralization have been compiled. The results show that the isotopic compositions are highly heterogeneous among these deposits with different ages and Mo tonnages, indicating that Mo-related magmas could be derived from either ancient lower crust or relatively juvenile lower crust or via mixing of mantle-derived magmas with varying proportions of crustal melts. This suggests that different magmas, independently from their sources, can produce Mo mineralization in NE China, and, therefore, that there was probably not an unusually Mo rich basement underlying NE China. In addition, Monte Carlo simulations have been carried out to explore the magmatic processes potentially associated with the formation of magmatic-hydrothermal (porphyry- or skarn-type) Mo deposits. The results reveal that a variably large magma volume (e.g., >150 km3) was required to provide enough Mo metal to form the large (>0.1 Mt Mo) deposits. In NE China, the Jurassic Mo deposits are much more abundant and larger than the Triassic and Cretaceous deposits, which could be attributed to the specific Jurassic tectonic regime. In the Jurassic, the subduction of the Paleo-Pacific oceanic plate led to regional compression, which favors accumulation of larger amounts of magmas at depth, ultimately resulting in larger Mo deposit formation. In this study, we highlight the importance of magma volume, rather than magma source, in the formation of the Mesozoic Mo deposits in NE China.

Chemical and isotopic systematics of the Caledonian intrusions of Scotland and Northern England: a guide to magma source region and magma-crust interaction

1984 ◽  
Vol 310 (1514) ◽  
pp. 709-742 ◽  
Keyword(s):  
Source Region ◽  
Thermal Conditions ◽  
Magma Source ◽  
Substantial Part ◽  
Upper Crust ◽  
Scottish Highlands ◽  
Late Proterozoic ◽  
Source Regions ◽  
Subducted Oceanic Crust ◽  
Lower Palaeozoic

Chemical and O-, Sr-, Nd-, and Pb-isotope relations for the British Caledonian granitoids exhibit systematic variations that are attributed to derivation from both mantle and crustal sources. The ‘older’ (more than ca . 470 Ma) pre- and syn-tectonic granites were the product of local anatectic melting of Late Proterozoic metasedimentary upper crust (8 18 O æ 8 to 14% 0 , 87 S r/ 86 Sr > 0.710, 206 Pb / 204 Pb « 18.1-19.2) during the peak thermal conditions of the Grampian Orogeny. The ‘younger’ (less than ca . 440 Ma) post-tectonic granitoids have a complex origin which, in individual cases, involved at least four different source regions: (i) the upper mantle or subducted oceanic crust (8 18 O « 5.7 to 7.0%o, 87 Sr/ 86 Sr « 0.7035-0.7040, 206 Pb/ 204 Pb = 17.9 to 18.1) and (ii) Lower Palaeozoic geosynclinal sedimentary upper crust (8 18 O « 11 to 14% 0 , 87 Sr/ 86 Sr « 705-0.711, 206 Pb/ 204 Pb « 18.4) within the paratectonic Caledonides in the Scottish Midland Valley and Southern Uplands and in Northern England or (iii) Middle Proterozoic (?) mafic to intermediate granulitic lower crust (8 18 O « 8 to 10% 0 , 87 Sr/ 86 Sr « 0.705-0.707, 206 Pb / 204 Pb « 16.5-17.0) and (iv) Middle to Late Proterozoic metasedimentary upper crust (8 18 0 « 8 to 14% 0 , 87 Sr/ 86 Sr > 0.710, 206 Pb/ 207 Pb » 18.1-19.2) in the Scottish Highlands. Mantle-derived magmas or their direct derivatives were likely involved in the development of all of the ‘younger’ granitoids, either as end-member components or as the source for a substantial part of the heat required for crustal melting and assimilation. Although the Lower Palaeozoic was a time during which a large amount of igneous material was introduced into the upper crust in Britain, it was not a major crust-forming period because the Caledonian granitoids are dominated by recycled continental crust.

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