scholarly journals Evidence of mingling between contrasting magmas in a deep plutonic environment: the example of Várzea Alegre, in the Ribeira Mobile Belt, Espírito Santo, Brazil

2001 ◽  
Vol 73 (1) ◽  
pp. 99-119 ◽  
Author(s):  
SILVIA R. MEDEIROS ◽  
CRISTINA M. WIEDEMANN-LEONARDOS ◽  
SIMON VRIEND
Keyword(s):  
Partial Melting ◽  
Granitic Magma ◽  
Geochemical Data ◽  
Mobile Belt ◽  
Tholeiitic Magma ◽  
Rock Types ◽  
Upper Proterozoic ◽  
Incompatible Elements ◽  
Wide Range ◽  
Intermediate Rock

At the end of the geotectonic cycle that shaped the northern segment of the Ribeira Mobile Belt (Upper Proterozoic to Paleozoic age), a late to post-collisional set of plutonic complexes, consisting of a wide range of lithotypes, intruded all metamorphic units. The Várzea Alegre Intrusive Complex is a post-collisional complex. The younger intrusion consists of an inversely zoned multistage structure envolved by a large early emplaced ring of megaporphyritic charnoenderbitic rocks. The combination of field, petrographic and geochemical data reveals the presence of at least two different series of igneous rocks. The first originated from the partial melting of the mantle. This was previously enriched in incompatible elements, low and intermediate REE and some HFS-elements. A second enrichment in LREE and incompatible elements in this series was due to the mingling with a crustal granitic magma. This mingling process changed the composition of the original tholeiitic magma towards a medium-K calc-alkalic magma to produce a suite of basic to intermediate rock types. The granitic magma from the second high-K, calc-alkalic suite originated from the partial melting of the continental crust, but with strong influence of mantle-derived melts.

scholarly journals Geoquímica do gabro coronítico de Amparo, RJ

2002 ◽  
Vol 25 ◽  
pp. 44-67
Author(s):  
Isabel Pereira Ludka ◽  
Cristina Maria Wiedemann
Keyword(s):  
Major Elements ◽  
Geochemical Data ◽  
Mobile Belt ◽  
Olivine Gabbro ◽  
Geochemical Analysis ◽  
Minor And Trace Elements ◽  
Tholeiitic Magma ◽  
Basic Rocks ◽  
The Town ◽  
Janeiro State

The aim of this paper is to present geochemical data and some petrological aspects of the Amparo gabbroic (hyperite) body, located approximately 30 km east of the town, Nova Friburgo, Rio de Janeiro State. Ten samples of these basic rocks were analysed for major, minor and trace elements, and three of these for REE. The data obtained reflect the limited mineralogical range. The contents of the major elements indicate a sub-alkalic tholeiitic magma, as shown by modal analysis, which classified these rocks as an olivine gabbro. Geochemical analysis of the minor, trace and rare-earth elements shows abnormal incompatible enrichment, such as the high LREE, Ba and Sr contents. Similar results for other basic and ultrabasic intrusions are common in this portion of the Ribeira Mobile Belt.

Petrogenesis of contrasting magmatic suites in the Abu Kharif area, Northern Eastern Desert, Egypt: implications for Pan-African crustal evolution and tungsten mineralization

2021 ◽  
pp. 1-27
Author(s):  
Nora G Abdel Wanees ◽  
Mohamed M El-Sayed ◽  
Khalil I Khalil ◽  
Hossam A Khamis
Keyword(s):  
Partial Melting ◽  
Fractional Crystallization ◽  
Eastern Desert ◽  
Granitic Magma ◽  
Geochemical Data ◽  
Calc Alkaline ◽  
Quartz Veins ◽  
Pan African ◽  
Granite Suite ◽  
Tungsten Mineralization

Abstract The Abu Kharif area in the Northern Eastern Desert consists of contrasting granitic magma suites: a Cryogenian granodiorite suite (850–635 Ma), an Ediacaran monzogranite suite (635–541 Ma) and a Cambrian alkali riebeckite granite suite (541–485 Ma). Tungsten mineralization occurs within W-bearing quartz veins and a disseminated type confined to the monzogranite. Whole-rock geochemical data classify the granodiorite as a late-orogenic I-type with calc-alkaline affinity, while the monzogranite and alkali riebeckite granite represent respectively a post-orogenic highly fractionated I-type with calc-alkaline affinity and an anorogenic A1-subtype with alkaline affinity. Geochemical modelling indicates that the three intrusions represent separate magmatic pulses where the granodiorite was generated by ∼75 % batch partial melting of an amphibolitic source followed by fractional crystallization of hornblende, biotite, apatite and titanite. The monzogranite was formed by 62 % batch partial melting of the normal ‘non-metasomatized’ Pan-African crust of calc-alkaline granite composition followed by fractional crystallization of plagioclase, biotite, K-feldspar, magnetite, ilmenite, with minor apatite and titanite. The alkali riebeckite granite was generated by 65 % batch partial melting of metasomatized Pan-African granite source followed by fractional crystallization of plagioclase, K-feldspar, amphibole and biotite with minor magnetite, apatite and titanite. In general, the parent magmas of the three intrusions were originally enriched in W, but with different concentrations. This W-enrichment would be caused by magmatic-related hydrothermal volatile-rich fluids and concentrated within the monzogranite.

scholarly journals Magmatism of the Kenya Rift Valley: a review

2002 ◽  
Vol 93 (3) ◽  
pp. 239-253 ◽  
Author(s):  
Ray Macdonald
Keyword(s):  
Partial Melting ◽  
Rift Valley ◽  
Volcanic Rocks ◽  
Mobile Belt ◽  
Kenya Rift ◽  
South Central ◽  
Northern Tanzania ◽  
Wide Range ◽  
High Level ◽  
Kenya Rift Valley

ABSTRACTTertiary–Recent magmatism in the Kenya Rift Valley was initiated c. 35 Ma, in the northern part of Kenya. Initiation of magmatism then migrated southwards, reaching northern Tanzania by 5–8 Ma. This progression was accompanied by a change in the nature of the lithosphere, from rocks of the Panafrican Mozambique mobile belt through reworked craton margin to rigid, Archaean craton. Magma volumes and the geochemistry of mafic volcanic rocks indicate that magmatism has resulted from the interaction with the lithosphere of melts and/or fluids from one or more mantle plumes. Whilst the plume(s) may have been characterised by an ocean island basalt-type component, the chemical signature of this component has everywhere been heavily overprinted by heterogeneous lithospheric mantle. Primary mafic melts have fractionated over a wide range of crustal pressures to generate suites resulting in trachytic (silica-saturated and-undersaturated) and phonolitic residua. Various Neogene trachytic and phonolitic flood sequences may alternatively have resulted from volatile-induced partial melting of underplated mafic rocks. High-level partial melting has generated peralkaline rhyolites in the south–central rift. Kenyan magmatism may, at some future stage, show an increasing plume signature, perhaps associated ultimately with continental break-up.

scholarly journals PLAGIOGRANITIC ROCKS OF EVROS OPHIOLITE, NE GREECE

2007 ◽  
Vol 40 (2) ◽  
pp. 884 ◽  
Author(s):  
A. Magganas
Keyword(s):  
Partial Melting ◽  
Fractional Crystallization ◽  
Geochemical Data ◽  
Incompatible Elements ◽  
Eu Anomaly ◽  
First Approximation ◽  
High Silica ◽  
Hydrothermal Metamorphism ◽  
Ree Patterns

Dykes or small stocks of plagiogranitic rocL· occur below the extrusive sequence and in mutually interpenetrating association with the sheeted dyke complex of the Evros Ophiolite, NE Greece. They are classified as tonalités, low silica trondhjemites (LST) and high silica trondhjemites (HST). Pétrographie and geochemical data suggest they resemble oceanic plagiogranites ofSSZ origin. Their normalized rock/ORG diagrams reveal ORG compatible element values, slightly depleted relative to ORG incompatible elements and Ba, Ta and Nb negative anomalies. Plagiogranites also show subparallel, relatively flat REE patterns with variable Eu anomaly. As such geochemical features are also found in the dacitic to rhyodacitic lavas of Evros Ophiolite, it is assumed that plagiogranitic melts, especially of LST composition, presumably fed them. As a first approximation to plagiogranites origin, it is suggested tonalité and HST could have been generated by 5-15 % partial melting of oceanic gabbros, whereas LST may possibly derive by fractional crystallization of a MORB type source. In a later stage, intense hydrothermal metamorphism affected the plagiogranites causing formation of peculiar epidositic spherical clots and veinlets

Lunar differentiation processes as characterized by trace element abundances

1977 ◽  
Vol 285 (1327) ◽  
pp. 199-205 ◽  
Keyword(s):  
Trace Element ◽  
Partial Melting ◽  
Melting Process ◽  
Reasonable Assumption ◽  
Lunar Crust ◽  
Crustal Layer ◽  
Element Abundances ◽  
Rock Types ◽  
Incompatible Elements ◽  
Partial Melting Process

The pattern of incompatible elements (K, Rb, Ba, r.e.e., H f etc.) is the same for most samples from the lunar highlands. It is suspected that this pattern of incompatible elements is typical for the whole lunar crust. This seems to be a reasonable assumption as one can show from heat flow data that a large part of the Moon’s total U (and consequently other incompatible elements) has to be concentrated in a thin crustal layer, which certainly contributes to the sampled highland rock types. It is supposed that a partial melting process of the major part of the Moon has extracted the trace elements from the interior into the crust. The patterns of incompatible elements of mare basalts are those expected if a second partial melting process were applied to the trace-element-depleted interior. Some consequences of this model are discussed. A relatively constant Sr and Eu distribution through the whole Moon is inferred, implying a positive Eu-anomaly in the lunar interior.

Early Cretaceous crust–mantle interaction linked to rollback of the Palaeo-Pacific flat-subducting slab: constraints from the intermediate–felsic volcanic rocks of the northern Great Xing’an Range, NE China

2021 ◽  
pp. 1-22
Author(s):  
Jia-Hao Jing ◽  
Hao Yang ◽  
Wen-Chun Ge ◽  
Yu Dong ◽  
Zheng Ji ◽  
...  
Keyword(s):  
Early Cretaceous ◽  
Volcanic Rocks ◽  
Geochemical Data ◽  
Calc Alkaline ◽  
Ne China ◽  
Asthenospheric Mantle ◽  
High K ◽  
Wide Range ◽  
Great Xing’An Range ◽  
Subducting Slab

Abstract Late Mesozoic igneous rocks are important for deciphering the Mesozoic tectonic setting of NE China. In this paper, we present whole-rock geochemical data, zircon U–Pb ages and Lu–Hf isotope data for Early Cretaceous volcanic rocks from the Tulihe area of the northern Great Xing’an Range (GXR), with the aim of evaluating the petrogenesis and genetic relationships of these rocks, inferring crust–mantle interactions and better constraining extension-related geodynamic processes in the GXR. Zircon U–Pb ages indicate that the rhyolites and trachytic volcanic rocks formed during late Early Cretaceous time (c. 130–126 Ma). Geochemically, the highly fractionated I-type rhyolites exhibit high-K calc-alkaline, metaluminous to weakly peraluminous characteristics. They are enriched in light rare earth elements (LREEs) and large-ion lithophile elements (LILEs) but depleted in high-field-strength elements (HFSEs), with their magmatic zircons ϵHf(t) values ranging from +4.1 to +9.0. These features suggest that the rhyolites were derived from the partial melting of a dominantly juvenile, K-rich basaltic lower crust. The trachytic volcanic rocks are high-K calc-alkaline series and exhibit metaluminous characteristics. They have a wide range of zircon ϵHf(t) values (−17.8 to +12.9), indicating that these trachytic volcanic rocks originated from a dominantly lithospheric-mantle source with the involvement of asthenospheric mantle materials, and subsequently underwent extensive assimilation and fractional crystallization processes. Combining our results and the spatiotemporal migration of the late Early Cretaceous magmatic events, we propose that intense Early Cretaceous crust–mantle interaction took place within the northern GXR, and possibly the whole of NE China, and that it was related to the upwelling of asthenospheric mantle induced by rollback of the Palaeo-Pacific flat-subducting slab.

Geochemistry and original nature of Precambrian khondalites in the Eastern Ghats, Orissa: a discussion

1991 ◽  
Vol 82 (1) ◽  
pp. 87-88 ◽  
Author(s):  
J. K. Nanda ◽  
U. C. Pati
Keyword(s):  
Major Part ◽  
Eastern Ghats ◽  
Geochemical Data ◽  
Mobile Belt ◽  
Indian Peninsula ◽  
Eastern Ghats Mobile Belt

While congratulating the authors for the wealth of geochemical data on a very important Precambrian lithological assemblage of India, known commonly as khondalites, which constitute a major part of the Eastern Ghats mobile belt bordering the eastern fringes of the Indian Peninsula, we have a few comments to offer on the hypothesis propounded by the authors (Dash et al. 1987).

Origin of the Ordovician Mansehra granite in the NW Himalaya, Pakistan: constraints from Sr–Nd isotopic data, zircon U–Pb age and Hf isotopes

2018 ◽  
Vol 481 (1) ◽  
pp. 277-298 ◽  
Author(s):  
Masatsugu Ogasawara ◽  
Mayuko Fukuyama ◽  
Rehanul Haq Siddiqui ◽  
Ye Zhao
Keyword(s):  
Granitic Magma ◽  
Geochemical Data ◽  
Large Contribution ◽  
Crustal Material ◽  
Sr Isotope ◽  
Nw Himalaya ◽  
Nd Isotope ◽  
Isotope Data ◽  
Late Neoproterozoic ◽  
T Values

AbstractThe Mansehra granite in the NW Himalaya is a typical Lesser Himalayan granite. We present here new whole-rock geochemistry, Rb–Sr and Sm–Nd isotope data, together with zircon U–Pb ages and Hf isotope data, for the Mansehra granite. Geochemical data for the granite show typical S-type characteristics. Zircon U–Pb dating yields 206Pb/238U crystallization ages of 483–476 Ma. The zircon grains contain abundant inherited cores and some of these show a clear detrital origin. The 206Pb/238U ages of the inherited cores in the granite cluster in the ranges 889–664, 1862–1595 and 2029 Ma. An age of 664 Ma is considered to be the maximum age of the sedimentary protoliths. Thus the Late Neoproterozoic to Cambrian sedimentary rocks must be the protolith of the Mansehra granitic magma. The initial Sr isotope ratios are high, ranging from 0.7324 to 0.7444, whereas the εNd(t) values range from −9.2 to −8.6, which strongly suggests a large contribution of old crustal material to the protoliths. The two-stage Nd model ages and zircon Hf model ages are Paleoproterozoic, indicating that the protolith sediments were derived from Paleoproterozoic crustal components.

scholarly journals Comparison of Magma Oxygen Fugacity and Zircon Hf Isotopes between Xianglushan Tungsten-Bearing Granite and Late Yanshanian Granites in Jiangxi Province, South China

Minerals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 106
Author(s):  
Xing-Yuan Li ◽  
Jing-Ru Zhang ◽  
Chun-Kit Lai
Keyword(s):  
Oxygen Fugacity ◽  
South China ◽  
Granitic Magma ◽  
Geochemical Data ◽  
Jiangxi Province ◽  
Magmatic Zircon ◽  
Late Mesozoic ◽  
Icp Ms ◽  
T Values ◽  
Southern Jiangxi Province

Jiangxi Province (South China) is one of the world’s top tungsten (W) mineral provinces. In this paper, we present a new LA-ICP-MS zircon U-Pb age and Hf isotope data on the W ore-related Xianglushan granite in northern Jiangxi Province. The magmatic zircon grains (with high Th/U values) yielded an early Cretaceous weighted mean U-Pb age of 125 ± 1 Ma (MSWD = 2.5, 2σ). Zircon εHf(t) values of the Xianglushan granite are higher (−6.9 to −4.1, avg. −5.4 ± 0.7) than those of the W ore-related Xihuanshan granite in southern Jiangxi Province (−14.9 to −11.2, avg. −12.5 ± 0.9), implying different sources between the W ore-forming magmas in the northern and southern Jiangxi Province. Compiling published zircon geochemical data, the oxygen fugacity (fO2) of the late Yanshanian granitic magmas in Jiangxi Province (the Xianglushan, Ehu, Dahutang, and Xihuashan plutons) were calculated by different interpolation methods. As opposed to the W ore-barren Ehu granitic magma, the low fO2 of the Xianglushan granitic magma may have caused W enrichment and mineralization, whilst high fO2 may have led to the coexistence of Cu and W mineralization in the Dahutang pluton. Additionally, our study suggests that the absence of late Mesozoic Cu-Mo mineralization in the Zhejiang, Jiangxi, and Anhui Provinces (Zhe-Gan-Wan region) was probably related to low fO2 magmatism in the Cretaceous.

scholarly journals Global whole-rock geochemical database compilation

2019 ◽  
Author(s):  
Matthew Gard ◽  
Derrick Hasterok ◽  
Jacqueline Halpin
Keyword(s):  
Database Management ◽  
Temporal Trends ◽  
Physical Property ◽  
Database Management System ◽  
Geochemical Data ◽  
Data Sets ◽  
Unique Contribution ◽  
Data Set ◽  
Wide Range ◽  
Geochemical Indices

Abstract. Dissemination and collation of geochemical data are critical to promote rapid, creative and accurate research and place new results in an appropriate global context. To this end, we have assembled a global whole-rock geochemical database, with other associated sample information and properties, sourced from various existing databases and supplemented with numerous individual publications and corrections. Currently the database stands at 1,023,490 samples with varying amounts of associated information including major and trace element concentrations, isotopic ratios, and location data. The distribution both spatially and temporally is quite heterogeneous, however temporal distributions are enhanced over some previous database compilations, particularly in terms of ages older than ~ 1000 Ma. Also included are a wide range of computed geochemical indices, physical property estimates and naming schema on a major element normalized version of the geochemical data for quick reference. This compilation will be useful for geochemical studies requiring extensive data sets, in particular those wishing to investigate secular temporal trends. The addition of physical properties, estimated by sample chemistry, represents a unique contribution to otherwise similar geochemical databases. The data is published in .csv format for the purposes of simple distribution but exists in a format acceptable for database management systems (e.g. SQL). One can either manipulate this data using conventional analysis tools such as MATLAB®, Microsoft® Excel, or R, or upload to a relational database management system for easy querying and management of the data as unique keys already exist. This data set will continue to grow, and we encourage readers to contact us or other database compilations contained within about any data that is yet to be included. The data files described in this paper are available at https://doi.org/10.5281/zenodo.2592823 (Gard et al., 2019).

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