5,858 research outputs found
Late Hercynian dyke magmatism of Sarrabus (SE Sardinia)
No full textThe late-Hercynian dyke magmatism of Sarrabus reflects the bimodal distribution observed in the other areas of Sardinia, the suite being represented by prevalent basaltic andesites and peraluminous rhyolites. Calcalkaline basalts and andesites are scarce, while dacites are extremely rare. The hypabyssal activity is closed by basaltic dykes with tholeiitic affinity. The chemical composition points out the 'medium-K' and 'high-K' character of the calcalkaline series. Fractionation links are lacking between calcalkaline and the majority of rhyolitic rocks. In comparison with dyke rocks of the other areas of Sardinia, many of the Sarrabus type show a more marked subalkaline character. The compositional variation of calcalkaline rocks can be partly explained by crystal-liquid fractionation processes. Among the rhyolitic rocks, two groups with different peraluminous characters have been recognized
Depositional processes of the mixed carbonate-siliciclastic rhodolith beds of the Miocene Saint-Florent Basin, northern Corsica
No full textMany sedimentary processes can lead to the formation of mixed carbonate-siliciclastic sediments in shallow shelf environments. The Miocene Saint-Florent Basin (Corsica), and in particular the Monte S. Angelo Formation, offers the possibility to analyze coarse mixed sediments produced by erosion of a rocky coast, ephemeral stream input, and shallow-water carbonate production dominated by red algae. The Monte S. Angelo Formation was deposited during the Burdigalian to Langhian interval. During this interval, the island of Corsica experienced increased subsidence related to the development of the Ligurian-Proven double dagger al Basin and associated Sardinia-Corsica block rotation. Four main rhodolith-rich subfacies have been recognized: conglomerate with rhodoliths, massive rhodolith rudstone, well-bedded rhodolith rudstone, and rhodolith floatstone. The four facies have been interpreted as having been deposited in different environments of a gravel-dominated, nearshore to offshore prograding wedge. Deep-water melobesioids dominate the red algal assemblage from shoreface to offshore. Shallow-water subfamilies of lithophylloids and mastophoroids occur in only accessory amounts. Poor illumination is believed to be due to terrigenous input by ephemeral streams and wave- and current-resuspension. Resuspension processes are favored by the limited occurrence of seagrasses. Two types of siliciclastic-carbonate mixing processes characterize the investigated rhodolith-rich deposits: (1) punctuated mixing, produced by the re-deposition of terrigenous sediments by debris-flow processes during flooding events onto carbonate sediments together with rhodoliths of the shoreface environments, and (2) in situ mixing, produced by growth of coralline algae on siliciclastic pebbles to form the rhodoliths.Many sedimentary processes can lead to the formation of mixed carbonate-siliciclastic sediments in shallow shelf environments. The Miocene Saint-Florent Basin (Corsica), and in particular the Monte S. Angelo Formation, offers the possibility to analyze coarse mixed sediments produced by erosion of a rocky coast, ephemeral stream input, and shallow-water carbonate production dominated by red algae. The Monte S. Angelo Formation was deposited during the Burdigalian to Langhian interval. During this interval, the island of Corsica experienced increased subsidence related to the development of the Ligurian-Provençal Basin and associated Sardinia-Corsica block rotation. Four main rhodolith-rich subfacies have been recognized: conglomerate with rhodoliths, massive rhodolith rudstone, well-bedded rhodolith rudstone, and rhodolith floatstone. The four facies have been interpreted as having been deposited in different environments of a gravel-dominated, nearshore to offshore prograding wedge.
Petrologia del magmatismo filoniano tardo-ercinico del Sarrabus (Sardegna sud-orientale)
No full textDottorato di ricerca in scienze della terra. 7. ciclo. A.a. 1991-95. Relatore G. Traversa. Coordinatore G. PialliConsiglio Nazionale delle Ricerche - Biblioteca Centrale - P.le Aldo Moro, 7, Rome; Biblioteca Nazionale Centrale - P.za Cavalleggeri, 1, Florence / CNR - Consiglio Nazionale delle RichercheSIGLEITItal
PROPENE/ETHENE-[1-13C] COPOLYMERIZATION AS A TOOL FOR INVESTIGATING CATALYST REGIOSELECTIVITY, 1 - THEORY AND CALIBRATION
No full textIn a previous letter, we proposed the synthesis and C-13 NMR characterization of propene/ethene-[1-C-13] copolymers at low ethene-[1-C-13] content as a convenient tool for measuring the regioselectivity of coordinated propene polyinsertion, in case 13C NMR fails to detect the regiomistakes in propene homopolymers. In the present article, we introduce the foundations of the approach in more detail, and illustrate how its scope can be extended to the evaluation of catalyst "dormancy" due to regiochemical monomer inversion. The method was calibrated for two well-known C-2-symmetric ansa-metallocene catalysts (namely, rac-Me2Si(1-indenyl)(2)ZrCl2 and rac-Me2Si(2-Me-4-phenyl-1-indenyl)(2)ZrCl2), by means of a cross-check with results of a C-13 NMR characterization of samples of poly(propene-[3-C-13]) prepared under corresponding experimental conditions. In particular, it was proved that the fraction of consecutive 2,1 insertions in propene homopolymerization promoted by the quoted catalysts, although nonzero, is low enough not to invalidate the propene/ethene-[1-C-13] copolymerization approach
Geochronology, Sr-Nd isotope geochemistry and petrology of Late-Hercynian dyke magmatism from Sarrabus (SE Sardinia)
No full textSedimentological analysis of the rhodolith rich deposits of Burdigalian Sant’Angelo Formation (Saint Florant, northern Corsica, France)
No full textDepositional processes of the carbonate-siliciclastic rhodolith rich deposits of Burdigalian Sant'Angelo Formation (Saint Florent, Northern Corsica, France)
No full textPost-Hercynian basic dyke magmatism of the Concas-Alà dei Sardi alignment (Northern Sardinia-Italy)
No full textPetrographic and mineral-glass chemical dataset of igneous rock clasts from Early Oligocene Aveto-Petrignacola Formation (Northern Italy)
No full textThis dataset article contains petrographic and mineral-glass chemical data of igneous rock clasts from Early Oligocene Aveto-Petrignacola Formation (APF; Northern Italy). Meth- ods for obtaining the dataset include optical microscopy, scanning electron microscopy and electron probe microanal- ysis. The APF volcanic rocks are basalts, basaltic andesites, andesites, dacites and rhyolites. Rare gabbroic cumulate nodules complete the dataset. Basalts are porphyritic, with calcic plagioclase (An 72–92 Ab 7–27 Or 0–1 ), ferroan enstatite (En 59–68 Fs 29–37 Wo 3–4 ) and augite (En 38–39 Fs 18–20 Wo 41–44 ) phenocrysts, in a hypocrystalline groundmass made up of bytownite (An 71–85 Ab 14–28 Or 1 ), augite (En 37–38 Fs 19 Wo 43–44 ), ferroan enstatite (En 62–68 Fs 30–35 Wo 1–4 ) and rare pigeonite (En 46–50 Fs 37–42 Wo 7–17 ). The basaltic andesites are porphyritic to glomeroporphyritic with phenocrysts of zoned plagio- clase (An 44–67 Ab 32–55 Or 1 ), orthopyroxene, Mg-rich augite (En 38–42 Fs 15–17 Wo 43–45 ), rare pargasite to edenite amphibole (Mg# 69–59) and very rare biotite in a hypocrystalline to holohyaline groundmass. Andesites are highly porphyritic with phenocrysts of plagioclase (An 47–79 Ab 20–52 Or 0–1 ), pargasite to magnesio-hornblende (Mg# 72–67), Mg-rich augite (En 43–46 Fs 12–17 Wo 41–43 ), subordinate ferroan enstatite (En 68–74 Fs 23–29 Wo 3–4 ), biotite (Mg# 53) and Ti-magnetite (Usp 29–41 ). Dacites (massive lavas and ignimbrites) are porphyritic, with phenocrysts and phenoclasts of plagioclase (An 33–79 Ab 20–62 Or 0–4 ), calcic amphibole (Ti-pargasite, Mg-hornblende and edenite; Mg# 81–46), biotite (Mg#67–56), very rare Mg-rich augite (En 41–42 Fs 16–18 Wo 40–43 ) and resorbed quartz in hypohyaline to holohyaline groundmass with a dense mat of anhedral quartz, labradorite-andesine (An 36–66 Ab 33–61 Or 1–4 ) and rare anorthoclase (An 22 Ab 66 Or 12 ).
Rhyolitic compositions have been found both as volcanic clasts (massive lava and ignimbrites) with andesine to oligoclase phenoclasts (An 25–38 Ab 61–71 Or 1–4 ), quartz, biotite (Mg# 55–53) and Ti-magnetite (Usp 18–77 ), and as interstitial glasses (residual melt drops) in other APF volcanic rocks. The cumulate nodules are olivine-gabbro and amphibolegabbro/gabbronorite with a mineral paragenesis dominatedby plagioclase (An 41–73 Ab 26–57 Or 1–3 ), olivine (Fo 68–72 ), Mg rich augite to ferroan diopside (En 41–45 Fs 12–15 Wo 42–45 ; Mg#79–74), ferroan enstatite (En 65–74 Fs 24–33 Wo 2–3 ; Mg# 76–68), magnetite (Usp 15–28 ) and titanian pargasite (Mg# 67–65). The main cumulus phases are plagioclase, olivine and pyroxene, while intercumulus/postcumulus phases are titanian pargasite and magnetite. The dataset can be used to compare petrographic features and chemical compositions of calcalkaline rocks emplaced in other subduction-related settings. Above all, it can represent a useful contribution in solving the problem linked to the identification of a hidden Early-Oligocene source of the thick volcaniclastic APF succession in the Alpine-Apennine belt geodynamic evolution
Mimicking Ziegler-Natta catalysts in homogeneous phase, Part 1 - C2-symmetric octahedral Zr(IV) complexes with tetradentate [ONNO]-type ligands
No full textPropene polymn. was carried out in the presence of 2 of the title Zr complexes, giving isotactic site-controlled or weakly syndiotactic chain-end-controlled polymers via highly regioselective 1,2 primary monomer insertion. The two catalysts are believed to be good models of Ziegler-Natta active species, albeit with lower abs. rates of chain propagation and transfer
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