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1.
The Alpine peridotite massif of Lanzo (Italy) contains three generations of basic dikes (gabbros and basalts). The older gabbros are plagioclase-rich mantle segregates while the younger gabbro dikes are cumulates very similar in chemical composition to recent oceanic gabbros and gabbros from ophiolitic complexes. They both were derived from the N-type mid-ocean ridge basalt (MORB) magmas which were progressively more depleted in incompatible elements and were probably generated during a dynamic melting of a rising mantle diapir. The basaltic dikes are the N-type MORB and closely resemble the Alpine-Apennine ophiolitic basalts. They were derived from a different upper mantle source than the parental magmas of the gabbros. The source of the basalts was less depleted in light REE. The presence of basic magmas with N-type MORB affinities in the Lanzo massif is consistent with the close genetic relationship between the Alpine peridotite body and the ophiolites of the Liguro-Piemontese basin. 相似文献
2.
Claudio Marchesi William L. Griffin Carlos J. Garrido Jean-Louis Bodinier Suzanne Y. O’Reilly Norman J. Pearson 《Contributions to Mineralogy and Petrology》2010,159(3):315-330
The western part of the Ronda peridotite massif (Southern Spain) consists mainly of highly foliated spinel-peridotite tectonites
and undeformed granular peridotites that are separated by a recrystallization front. The spinel tectonites are interpreted
as volumes of ancient subcontinental lithospheric mantle and the granular peridotites as a portion of subcontinental lithospheric
mantle that underwent partial melting and pervasive percolation of basaltic melts induced by Cenozoic asthenospheric upwelling.
The Re–Os isotopic signature of sulfides from the granular domain and the recrystallization front mostly coincides with that
of grains in the spinel tectonites. This indicates that the Re–Os radiometric system in sulfides was highly resistant to partial
melting and percolation of melts induced by Cenozoic lithospheric thermal erosion. The Re–Os isotopic systematics of sulfides
in the Ronda peridotites thus mostly conserve the geochemical memory of ancient magmatic events in the subcontinental lithospheric
mantle. Os model ages record two Proterozoic melting episodes at ~1.6 to 1.8 and 1.2–1.4 Ga, respectively. The emplacement
of the massif into the subcontinental lithospheric mantle probably coincided with one of these depletion events. A later metasomatic
episode caused the precipitation of a new generation of sulfides at ~0.7 to 0.9 Ga. These Proterozoic Os model ages are consistent
with results obtained for several mantle suites in Central/Western Europe and Northern Africa as well as with the Nd model
ages of the continental crust of these regions. This suggests that the events recorded in mantle sulfides of the Ronda peridotites
reflect different stages of generation of the continental crust in the ancient Gondwana supercontinent. 相似文献
3.
Antal?Embey-IsztinEmail author Gábor?Dobosi Jean-Louis?Bodinier Delphine?Bosch G.?A.?Jenner Simone?Pourtales Olivier?Bruguier 《Contributions to Mineralogy and Petrology》2014,168(3):1054
Peridotite xenoliths erupted by alkali basaltic volcanoes in the western Pannonian Basin can be divided into two fundamentally contrasting groups. Geochemical characteristics of the abundant protogranular, porphyroclastic and equigranular nodules suggest that these samples originate from an old consolidated and moderately depleted lithospheric mantle domain. In contrast, the geochemical features of the worldwide rare, but in the Pannonian Basin relatively abundant, poikilitic xenoliths attest to a more complex evolution. It has been argued that the origin of the peculiar texture and chemistry may be intimately linked to melt/rock reactions at successively decreasing liquid volumes in a porous melt flow system. The most likely site where such reactions can take place is the asthenosphere–lithosphere boundary. In this context, poikilitic xenoliths may provide petrological and geochemical evidence for reactions between magmatic liquids issued from the uprising asthenosphere and the solid mantle rocks of the lithosphere. These reactions are important agents of the thermal erosion of the lithosphere; thus, they could have considerably contributed to the thinning of the lithosphere in the Pannonian region. We suggest that in the Pannonian Basin, there could be a strong relation between the unusual abundance of poikilitic mantle xenoliths and the strongly eroded lithosphere. 相似文献
4.
Submarine reworking of exhumed subcontinental mantle rocks: field evidence from the Lherz peridotites,French Pyrenees 总被引：1，自引：0，他引：1
In the Pyrenees, the lherzolites nowhere occur as continuous units. Rather, they always outcrop as restricted bodies, never more than 3 km wide, scattered across Mesozoic sedimentary units along the North Pyrenean Fault. We report the results of a detailed analysis of the geological setting of the Lherz massif (central Pyrenees), the type‐locality of lherzolites and one of the most studied occurrences of mantle rocks worldwide. The Lherz body is only 1.5 km long and belongs to a series of ultramafic bodies of restricted size (a few metres to some hundreds of metres), occurring within sedimentary formations composed mostly of carbonate breccias originating from the reworking of Mesozoic platform limestones and dolomites. The clastic formations also include numerous layers of polymictic breccias reworking lherzolitic clasts. These layers are found far from any lherzolitic body, implying that lherzolitic clasts cannot derive from the in situ fragmentation of an ultramafic body alone, but might also have been transported far away from their sources by sedimentary processes. A detailed analysis of the contacts between the Lherz ultramafic body and the surrounding limestones confirms that there is no fault contact and that sediments composed of ultramafic material have been emplaced into fissures within the brecciated carapace of the peridotites. These observations bear important constraints for the mode of emplacement of the lherzolite bodies. We infer that mantle exhumation may have occurred during Albian strike‐slip deformation linked to the rotation of Iberia along the proto‐North Pyrenean Fault. 相似文献
5.
J. L. Bodinier C. Dupuy J. Dostal F. Carme 《Contributions to Mineralogy and Petrology》1982,78(4):379-388
The ophiolite complex of Chamrousse (Belledonne Massif, Alps), consists of mafic to ultramafic cumulates and non-cumulates metamorphosed to amphibolite facies grade. The non-cumulitic rocks are similar in chemical composition to recent ocean-floor olivine tholeiites (both N-type and enriched P-type). The distribution of lithophile elements shows that the non-cumulitic rocks represent several magmas of different parentage. The character of the magmas varies according to the time of emplacement.Geological and geochemical data suggest that the Chamrousse complex was formed at a spreading oceanic ridge. The dynamic partial melting of an upper mantle diapir generated tholeiitic melt which decreased in amount and in REE contents. The first melt, enriched in light REE, was generated along the axis of the ridge while the second batch of melt, of lesser quantity and slightly depleted in light REE, was emplaced on the flank of the ridge. The third melt formed cross-cutting dikes with REE abundances typical of N-type (strongly light REE depleted) mid-ocean ridge basalts. 相似文献
6.
Y.-G. Xu M. A. Menzies J.-L. Bodinier R. M. Bedini P. Vroon J.-C. C. Mercier 《Contributions to Mineralogy and Petrology》1998,132(1):65-84
Poikiloblastic harzburgite xenoliths (P-type) from Borée, France are characterised by large (>1 cm), essentially unstrained
olivines and high equilibrium temperatures (>1200 °C). Mineralogical data, trace element abundances and Sr-Nd-O isotopes of
the constituent minerals are consistent with formation as a result of melt percolation-reactions in a lherzolite precursor
during lithospheric erosion by an upwelling plume. This petrogenetic model contrasts with previous models involving isochemical
recrystallisation from a granular lherzolite precursor (G-type) or derivation as metacumulates from tholeiitic magmas. Numerical
simulation of percolation reactions at the lithosphere-plume boundary using the plate model of Vernières et al. (1997) indicates
that the different textured xenoliths may represent mantle from different levels in a percolation-reaction column. If correct
then the P-type harzburgites resulted from pyroxene-dissolving and olivine-producing reactions at increasing melt fraction
(>3%) at the lower part of column (base of the lithosphere), whereas the G-type lherzolites were located within the low-porosity
domain (<0.1%) above a permeability barrier, and are formed through a melt-rock reaction at decreasing melt mass. Given the
very low melt fraction, the REE fractionation in this zone is controlled by chromatographic effects coupled with source effects
of reaction. The variations in porosity, melt/rock ratio and melt-rock reaction mechanism are believed to be responsible for
the diversity of REE patterns and striking correlation between REE abundance and texture in Borée xenoliths.
Received: 15 June 1997 / Accepted: 7 January 1998 相似文献
7.
Dmitri?A.?IonovEmail author Vladimir?S.?Prikhodko Jean-Louis?Bodinier Alexander?V.?Sobolev Dominique?Weis 《Contributions to Mineralogy and Petrology》2005,149(6):647-665
We provide petrographic, major and trace element data for over 30 spinel peridotite xenoliths from the Tokinsky Stanovik (Tok) volcanic field on the Aldan shield to characterize the lithospheric mantle beneath the south-eastern margin of the Siberian craton, which formed in the Mesoproterozoic. High equilibration temperatures (870–1,010°C) of the xenoliths and the absence of garnet-bearing peridotites indicate a much thinner lithosphere than in the central craton. Most common among the xenoliths are clinopyroxene-poor lherzolites and harzburgites with Al2O3 and CaO contents nearly as low as in refractory xenoliths from kimberlite pipes (Mir, Udachnaya) in the central and northern Siberian craton. By contrast, the Tok peridotites have higher FeO, lower Mg-numbers and lower modal orthopyroxene and are apparently formed by shallow partial melting (3 GPa). Nearly all Tok xenoliths yield petrographic and chemical evidence for metasomatism: accessory phlogopite, amphibole, phosphates, feldspar and Ti-rich oxides, very high Na2O (2–3.1%) in clinopyroxene, LREE enrichments in whole-rocks.Electronic Supplementary Material Supplementary material is available for this article at 相似文献
8.
9.
Origin of the recrystallisation front in the Ronda peridotite by km-scale pervasive porous melt flow 总被引：5，自引：0，他引：5
It is well established that porous melt flow in the upper mantle may significantly affect partial mantle melt compositions.
Less well established are the length-scale of porous flow and whether porous melt flow can be a volumetrically important magmatic
process. The only source for observations concerning the length-scale and nature of pervasive porous melt flow are peridotite
massifs. Here we present such observations in the form of structural, and major and trace element data from peridotites of
the Ronda massif, southern Spain. Trace element concentrations were obtained with high analytical precision (ICP-MS) and include
trace elements rarely analysed in peridotites, such as Rb, Th, Nb and Ta. The western portion of the Ronda massif can be divided
into two structural facies. The first and oldest is composed of deformed, porphyroclastic spinel peridotites, the second of
virtually undeformed granular spinel peridotites. They are separated by a recrystallisation front across which grain growth
of all phases occurred. The granular domain can be further subdivided into three subfacies: coarse-granular, fine-granular,
and layered-granular peridotites. According to structural facies, km-scale spatial variations unrelated to Ca and Al abundances
have been recognised for mg-numbers [atomic Mg/(Mg±Fe)] and incompatible elements such as rare earth elements (REE), Th and
high-field-strength elements (HFSE; including Ti). Such variations are reminiscent of those commonly ascribed to mantle metasomatism,
but have never been documented on the km-scale. The origin of the recrystallisation front is related to km-scale pervasive
melt percolation. Feed-back processes between grain growth and melt fraction could have led to important accumulation of melt
at the recrystallisation front, accomplished mainly by melting/dissolution. Variation in melt fraction across the front explains
the spatial variation in the degree of recrystallisation, mg-numbers, REE fractionation, and HFSE abundances, and could account
for many of the classical differences between basalts from convergent and extensional tectonic settings. Whereas the coarse-granular
peridotites reflect a stage of steady-state pervasive porous melt flow, the fine- and layered-granular facies probably reflect
the terminate stages of porous melt flow. Processes associated with both domains are pyroxene-forming freezing reactions at
decreasing melt volumes, and progressive channelling of melt flow associated with olivine-producing reactions. Both processes
show complex overprinting relationships in both time and space.
Received: 10 January 1995/Accepted: 1 September 1995 相似文献
10.
A. Leyreloup J. L. Bodinier C. Dupuy J. Dostal 《Contributions to Mineralogy and Petrology》1982,79(1):68-75
Granulitic xenoliths, enclosed in Neogene alkali basalts from the Atakor and Adrar N'Addjer volcanic massifs in Central Hoggar, southern Algeria, include mafic metaigneous and felsic metasedimentary rocks. The main mineral phases of metaigneous xenoliths are plagioclase and pyroxenes whereas quartz, feldspars, sillimanite, garnet and sapphirine occur in metasedimentary granulites. The metaigneous xenoliths represent a magmatic sequence of cumulitic and non-cumulitic rocks which resembles gabbroic bodies associated with anorthosites and has calc-alkaline affinities. Similar types and distributions of granulitic xenoliths are widespread and are probably characteristic of the lower crust in general, suggesting its homogeneity on a large scale but heterogencity on a local scale. 相似文献