Genesis of the Eastern Adamello Plutons (Northern Italy): Inferences for the Alpine Geodynamics

Geosciences ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 13
Author(s):  
Alessio Relvini ◽  
Silvana Martin ◽  
Bruna B. Carvalho ◽  
Giacomo Prosser ◽  
Luca Toffolo ◽  
...  
Keyword(s):  
Fractional Crystallization ◽  
Eastern Alps ◽  
Thermodynamic Modelling ◽  
Magmatic Complex ◽  
Minor Elements ◽  
Ne Italy ◽  
Isotopic Analyses ◽  
Eastern Border ◽  
Geochemical Analyses ◽  
Best Fit

The Corno Alto–Monte Ospedale magmatic complex crops out at the eastern border of the Adamello batholith, west of the South Giudicarie Fault (NE Italy). This complex includes tonalites, trondhjemites, granodiorites, granites and diorites exhibiting an unfoliated structure suggesting passive intrusion under extensional-to-transtensional conditions. Major, minor elements, REE and isotopic analyses and geochemical and thermodynamic modelling have been performed to reconstruct the genesis of this complex. Geochemical analyses unravel a marked heterogeneity with a lack of intermediate terms. Samples from different crust sections were considered as possible contaminants of a parental melt, with the European crust of the Serre basement delivering the best fit. The results of the thermodynamic modelling show that crustal melts were produced in the lower crust. Results of the geochemical modelling display how Corno Alto felsic rocks are not reproduced by fractional crystallization nor by partial melting alone: their compositions are intermediate between anatectic melts and melts produced by fractional crystallization. The tectonic scenario which favored the intrusion of this complex was characterized by extensional faults, active in the Southalpine domain during Eocene. This extensional scenario is related to the subduction of the Alpine Tethys in the Eastern Alps starting at Late Cretaceous time.

Discovery of Llandovery (Silurian) graptolites and probable Devonian corals in the Southalpine Metamorphic Basement of the Eastern Alps (Agordo, NE Italy)

2005 ◽  
Vol 142 (1) ◽  
pp. 1-5 ◽  
Author(s):  
IGINIO DIENI ◽  
DANILO GIORDANO ◽  
DAVID K. LOYDELL ◽  
FRANCESCO P. SASSI
Keyword(s):  
Shear Zone ◽  
Local Strain ◽  
Eastern Alps ◽  
Strain Partitioning ◽  
Ne Italy ◽  
Metamorphic Basement ◽  
Depositional Age ◽  
Devonian Age ◽  
Age Range

We report the discovery of Aeronian (Middle Llandovery) graptolites, and corals of probable Devonian age, in boudins hosted by greenschists, within the Southalpine Metamorphic Basement. These discoveries provide key constraints to the depositional age range of the protoliths. This remarkable occurrence of almost undeformed graptolites and compound corals in boudins within a metamorphic shear zone indicates very marked local strain partitioning.

scholarly journals Using Whole Rock and Zircon Geochemistry to Assess Porphyry Copper Potential of the Tonggou Copper Deposit, Eastern Tianshan

Minerals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 584
Author(s):  
Xue-Bing Zhang ◽  
Feng-Mei Chai ◽  
Chuan Chen ◽  
Hong-Yan Quan ◽  
Ke-Yong Wang ◽  
...  
Keyword(s):  
Fractional Crystallization ◽  
Porphyry Copper ◽  
Copper Deposit ◽  
Middle Part ◽  
Orogenic Belt ◽  
Geochemical Data ◽  
Eastern Tianshan ◽  
Porphyry Cu ◽  
Central Asian ◽  
Geochemical Analyses

Eastern Tianshan hosts a number of porphyry Cu deposits. However, these mainly formed in the Jueluotage Belt, in the middle part of Eastern Tianshan. The Tonggou porphyry Cu mineralization is an exception to this, since it is located in the Bogda Orogenic Belt, north of Eastern Tianshan. We obtained new zircon U-Pb ages, whole-rock geochemical data, zircon Hf isotope data, and zircon trace element compositions. LA-ICP-MS zircon U-Pb dating indicates a crystallization age of 302.2–303.0 Ma for the Tonggou mineralized granodiorite (TMG), which suggests that the Tonggou porphyry Cu mineralization formed in the Late Carboniferous period. εHf (t) data (1.8–14.1) for TMG suggests it was sourced from juvenile crustal melts, mixed with some mantle materials. TMG displays low ΣREE, compatible elements (Ba, Sr, Zr, and Hf), Zr/Hf and Nb/Ta ratios, as well as clearly negative Eu anomalies in whole rocks analyses. In addition, TMG is enriched in P, Hf and Th/U ratios in zircon, and has lower crystallization temperatures (734 to 735 °C) than the Daheyan barren granodiorite (DBG) (753 to 802 °C). Whole rock and zircon geochemical analyses show that the TMG was formed by fractional crystallization to a greater extent than the DBG in the Bogda Orogenic Belt. Moreover, zircon grains of the TMG show high Ce4+/Ce3+ ratios (159–286), which are consistent with related values from large porphyry deposits of the Central Asian Orogenic Belt (CAOB). High Ce4+/Ce3+ ratios reflect oxidizing magmas as a result of fractional crystallization, which indicates that the Tonggou deposit has potential to host a large porphyry Cu deposit.

Archean Boninite-like Rocks of the Northwestern Youanmi Terrane, Yilgarn Craton: Geochemistry and Genesis

2019 ◽  
Vol 60 (11) ◽  
pp. 2131-2168 ◽  
Author(s):  
Jack R Lowrey ◽  
Derek A Wyman ◽  
Tim J Ivanic ◽  
R Hugh Smithies ◽  
Roland Maas
Keyword(s):  
Trace Element ◽  
Crustal Contamination ◽  
Mantle Metasomatism ◽  
Chemical Compositions ◽  
Yilgarn Craton ◽  
Fine Grained ◽  
Mafic Intrusions ◽  
Field Evidence ◽  
Isotopic Analyses ◽  
Geochemical Analyses

Abstract Rocks with chemical compositions similar to Cenozoic boninites occur in many Archean cratons (boninite-like rocks), but they are rarely well-preserved, well-sampled, or presented within chrono- and chemo-stratigraphic context. This study provides a detailed description of the most extensive and well-preserved Archean boninite-like rocks reported to date. Within the 2820 to 2740 Ma magmatic suites of the northwest Youanmi Terrane, Yilgarn Craton, boninite-like rocks occur as two distinct units. The first boninite-like unit is thinner (several 10 s of m thick), occurs close to the base of the 2820–2800 Ma Norie Group and includes both volcanic flows and subvolcanic intrusions. The second boninite-like unit is thicker (locally several 100 s m), occurs near the base of the 2800–2740 Ma Polelle Group and consists of mainly fine-grained volcanic flows with local cumulate units. On average, major and trace element compositions for Youanmi Terrane boninite-like rocks are marginal between basalt, picrite and boninite and they have asymmetrically concave REE patterns, and Th–, Zr–Hf enrichments, similar to many Phanerozoic low-Si boninite suites, but at generally higher MREE–HREE contents. We report over 300 new whole-rock geochemical analyses, and 16 new Sm–Nd isotopic analyses, and associated petrographic evidence, including representative mineral compositions, which we support with published geochemical analyses and several decades of fieldwork in our study area. Comparison between Archean boninite-like rocks and Cenozoic boninites shows that most Archean examples had less depleted sources. We consider two possible petrogenetic models for the Youanmi Terrain examples: (1) they reflect variably contaminated komatiites, or (2) they reflect melts of metasomatised refractory mantle, analogous to Phanerozoic boninites. Trace element modelling indicates that crustal contamination could potentially produce rocks with boninite-like compositions, but requires an Al-enriched komatiitic parent liquid, for which there is no field evidence in our study area. Initial εNdT values in pre-2800 Ma rocks (εNdT -0·4 to +1·2) are on average slightly higher than those in 2800–2733 Ma examples (εNdT -3·2 to +1·2), compatible with increasing mantle metasomatism involving recycling of ≥ 2950 Ma crust. Integration of trace element and Nd isotopic data demonstrates that significant direct crustal assimilation was restricted to felsic magmas. The Th–Nb and Ba–Th systematics of mafic-intermediate rocks reflect fluid- and sediment-derived processes in the mantle, with boninite-like examples being linked primarily to fluid metasomatism. We compare the well-preserved igneous textures and mineralogy of Youanmi Terrane boninite-like rocks with those of their Phanerozoic counterparts, and based on studies of the latter, suggest that former had similarly hot, H2O-rich parent magmas. The association of boninite-like rocks in the Norie and Polelle Groups with coeval high-Mg andesites, sanukitoids and hydrous mafic intrusions of the Narndee Igneous Complex strongly suggests a metasomatised mantle source and subduction operating in the Yilgarn between 2820 and 2730 Ma.

Petrochemistry of Paleozoic spilites of the eastern Alps (Austria)

1973 ◽  
Vol 110 (1) ◽  
pp. 19-28 ◽  
Author(s):  
J. Loeschke
Keyword(s):  
Low Temperature ◽  
Fractional Crystallization ◽  
Basaltic Magma ◽  
Eastern Alps ◽  
Pillow Lavas ◽  
Secondary Origin ◽  
External Sources ◽  
Primary Minerals

SummaryIn the Karawanken Mountains (SE Austria) spilites (pillow lavas and sills) are found intercalated in a sequence of Paleozoic slates and graywackes. The petrogenesis of these spilites is interpreted as follows: The pillow lavas and sills consolidated as mugearites and hawaiites, which were derived from an alkali olivine-basaltic magma by fractional crystallization. Under low temperature metamorphic conditions water entered into the rocks predominantly from external sources. The primary minerals (Na-Ca plagioclase, pyroxene and glass) were thus replaced either partially or completely by minerals characteristic of spilites (albite, chlorite, epidote and others). The spilites analysed are of secondary origin. They are compared with spilites and basalts of other (continental and oceanic) areas.

Geochemical underpinnings of Australia's offshore hydrocarbon prospectivity

2014 ◽  
Vol 54 (1) ◽  
pp. 415
Author(s):  
Marita Bradshaw ◽  
Dianne Edwards ◽  
Chris Boreham ◽  
Emmanuelle Grosjean ◽  
Jennifer Totterdell ◽  
...  
Keyword(s):  
Source Rock ◽  
Lower Triassic ◽  
Source Rocks ◽  
Petroleum Systems ◽  
Isotopic Analyses ◽  
Marine Source ◽  
History Of ◽  
Hydrocarbon Sources ◽  
Geochemical Analyses ◽  
Gippsland Basin

Molecular and isotopic analyses of oils and gases can provide information on the depositional environment, maturation and age of their source rocks, and the post expulsion history of the hydrocarbons generated. Source rock analyses can determine their potential to generate hydrocarbons of varying type over specific thermal ranges, as well as demonstrating the strength of oil- or gas-to-source correlations. Together, this geochemical interpretation can provide insights about the extent of petroleum systems and can help delineate the relationships between hydrocarbon occurrences in a basin and across the continent. Oils that do not fit the well-established framework of oil families and Australian petroleum systems point to new source rock fairways. Examples include vagrant oils with lacustrine affinities found at various locations on the western Australian margin. Other examples are oil occurrences in the Gippsland Basin whose geochemical signatures contrast with the dominant non-marine oils, supporting the existence of a viable marine source rock facies. In under-explored and frontier basins, geochemical analyses of potential source rocks can provide key evidence to underpin new exploration efforts. For example, the recent acreage uptake in the Bight Basin was supported by Geoscience Australia’s recovery and analysis of oil-prone marine source rocks, and in the northern Perth Basin by new geochemical analysis extending the distribution of Lower Triassic Hovea marine source rocks offshore. Geoscience Australia has now embarked on a regional petroleum geological program that includes a national source rock study aimed at identifying and characterising Australia’s hydrocarbon sources, families and systems.

HT–LP crustal syntectonic anatexis as a source of the Permian magmatism in the Eastern Southern Alps: evidence from xenoliths in the Euganean trachytes (NE Italy)

2020 ◽  
Vol 177 (6) ◽  
pp. 1211-1230
Author(s):  
Raffaele Sassi ◽  
Claudio Mazzoli ◽  
Renaud Merle ◽  
Valentina Brombin ◽  
Massimo Chiaradia ◽  
...  
Keyword(s):  
Eastern Alps ◽  
Isotopic Signature ◽  
Southern Alps ◽  
Crustal Component ◽  
Content Type ◽  
Crustal Rocks ◽  
Ne Italy ◽  
Crustal Thinning ◽  
Supplementary Material ◽  
Migmatitic Gneiss

Oligocene trachytes from the Euganean Hills include various regionally metamorphosed gneissic and granulitic xenoliths. These xenoliths provide the unique opportunity to investigate South Alpine intermediate to deep crustal levels that are not at present exposed in the Eastern Alps. The estimated P–T conditions are in the range of 780–850°C and 0.45–0.55 GPa for a migmatitic gneiss xenolith. Sensitive high-resolution ion microprobe (SHRIMP II) U–Pb analyses on zircon from this xenolith provide concordant ages around 259.7 ± 3.5 Ma, consistent with a proton-induced X-ray emission (PIXE) U–Th–Pb age on monazite of 262 ± 12 Ma. The Sr–Nd–Pb isotopic compositions, and major and trace element data show distinct origins for the different types of xenoliths. Mafic granulite xenoliths have an isotopic signature close to mantle-derived rocks and to Permian gabbroic rocks from the Western Southern Alps. Metapelite xenoliths have high Sr and low Nd initial ratios like those of acid crustal rocks and could possibly represent the source of the crustal component that is dominant in the acid Permian supervolcanoes. The migmatitic xenolith provides the first documented evidence for a Permian thermal event associated with crustal thinning in the Eastern Southern Alps. Here the South Alpine basement escaped most of the Alpine crustal shortening and still preserves most of the original Permian extension under thick Mesozoic cover.Supplementary material: Microprobe analyses of mineralogical phases and Ti-in-biotite geothermometric calculations are available at https://doi.org/10.6084/m9.figshare.c.5032337

Fossil submarine hydrothermalism in metabasalts from the Gudon (Bressanone) amphibolite (Southalpine basement, Eastern Alps, NE Italy)

2018 ◽  
Vol 30 (2) ◽  
pp. 355-366 ◽  
Author(s):  
Dario Visonà ◽  
Christine M. Meyzen ◽  
Paolo Nimis ◽  
Fabrizio Nestola
Keyword(s):  
Eastern Alps ◽  
Ne Italy ◽  
Southalpine Basement

scholarly journals Is it possible to study palaeoenvironmental changes in Alpine spring habitats? A few examples from the south-eastern Alps (NE Italy)

2011 ◽  
Vol 70 (1s) ◽  
pp. 155 ◽  
Author(s):  
Maria Letizia FILIPPI ◽  
Gayane PILIPOSIAN ◽  
Laura MARZIALI ◽  
Nicola ANGELI ◽  
Valeria LENCIONI ◽  
...  
Keyword(s):  
Eastern Alps ◽  
The South ◽  
South Eastern ◽  
Ne Italy ◽  
Palaeoenvironmental Changes

Closure of India–Asia collision margin along the Shyok Suture Zone in the eastern Karakoram: new geochemical and zircon U–Pb geochronological observations

2020 ◽  
Vol 157 (9) ◽  
pp. 1451-1472 ◽  
Author(s):  
Shailendra Pundir ◽  
Vikas Adlakha ◽  
Santosh Kumar ◽  
Saurabh Singhal
Keyword(s):  
Fractional Crystallization ◽  
Late Cretaceous ◽  
Inductively Coupled Plasma ◽  
Active Continental Margin ◽  
Oceanic Lithosphere ◽  
Suture Zone ◽  
Geochemical Evolution ◽  
Geochronological Data ◽  
Inductively Coupled ◽  
Geochemical Analyses

AbstractNew whole-rock geochemical analyses along with laser ablation multi-collector inductively coupled plasma mass spectrometry U–Pb zircon ages of the granite–rhyolite from the Karakoram Batholith, exposed along the Shyok Valley, NW India, have been performed to understand the timing and geochemical evolution of these magmatic bodies and their implications for the geodynamic evolution of the Karakoram Batholith. New geochronological data on granites and rhyolites along with previously published geochronological data indicate that the Karakoram Batholith evolved during Albian time (~110–100 Ma) owing to the subduction of Tethys oceanic lithosphere along the Shyok Suture Zone. This region witnessed a period of no magmatism during ~99–85 Ma. Following this, the Kohistan–Ladakh arc and Karakoram Batholith evolved as a single entity in Late Cretaceous and early Palaeogene times. Late Cretaceous (~85 Ma) rhyolite intrusions within the Karakoram Batholith show calc-alkaline subduction-related signatures with a highly peraluminous nature (molar A/CNK = 1.42–1.81). These intrusions may have resulted from c. ~13.8 % to ~34.5 % assimilation of pre-existing granites accompanied by fractional crystallization during the ascent of the magma. The contamination of mantle wedge-derived melts with crust of the active continental margin of the Karakoram most likely enhanced the high peraluminous nature of the rhyolite magma, as has been constrained by assimilation fractional crystallization modelling. Two granite samples from the contact of the Shyok Metamorphic Complex and Karakoram Batholith indicate that the post-collisional Miocene magmatism was not only confined along the Karakoram Fault zone but also extends ~30 km beyond the Shyok–Muglib strand.

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