Retrograde <i>P‐T‐t</i> path for the Voltri Massif eclogites (Ligurian Alps, Italy): some tectonic implications

Messiga, Bruno; Scambelluri, Marco

doi:10.1111/j.1525-1314.1991.tb00506.x

Cited by 63 publications

(35 citation statements)

References 43 publications

(50 reference statements)

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“…The P – T path of the western Tianshan eclogites is quite different to that of the blueschists and eclogites from the Franciscan ( Ernst, 1988), Dora Maira ( Dobretsov, 1991), Sambagawa ( Maruyama et al ., 1996 ) or Qiling‐Dabie‐Sulu belt ( Wang et al ., 1992 ; Zhang & Liou, 1994; Zhang et al ., 1995 ). However, it appears to be similar to the Voltri eclogites in the western Alps ( Messiga & Scambelluri, 1991). Moreover, the P – T path of the metabasic blueschists in the Kekesu section ( Gao et al ., 1995 ) is quite different to that of the HP–LT rocks of the Akeyazhi and the Changawuzhi sections.…”

Section: Metamorphic Evolution Of Hp–lt Rockssupporting

confidence: 62%

“…8) 4 Lws+Jd 50 = 2 Zo+Pg+Qtz+6H 2 O ( Heinrich & Althaus, 1988) and Pg=Jd 50 +Ky+H 2 O ( Holland, 1979). These peak P – T conditions of 14–21 kbar and 530±50 °C of the western Tianshan HP–LT rocks are similar to those of other HP–LT regimes worldwide, such as the Jenner eclogites in California ( Krogh et al ., 1994 ), eclogite exotic blocks in the Franciscan complex ( Moore & Blake, 1989), Voltri eclogites ( Messiga & Scambelluri, 1991; Vallis & Scambelluri, 1996) and Sesia‐Lanzo eclogites in the western Alps ( Kienast et al ., 1991 ).…”

Section: Metamorphic Evolution Of Hp–lt Rocksmentioning

confidence: 99%

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P–T path of high‐pressure/low‐temperature rocks and tectonic implications in the western Tianshan Mountains, NW China

Gao

Klemd

Zhang

et al. 1999

Journal Metamorphic Geology

172

141

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The Chinese western Tianshan high‐pressure/low‐temperature (HP–LT) metamorphic belt, which extends for about 200 km along the South Central Tianshan suture zone, is composed of mainly metabasic blueschists, eclogites and greenschist facies rocks. The metabasic blueschists occur as small discrete blocks, lenses, bands, laminae or thick beds in meta‐sedimentary greenschist facies country rocks. Eclogites are intercalated within blueschist layers as lenses, laminae, thick beds or large massive blocks (up to 2 km2 in plan view). Metabasic blueschists consist of mainly garnet, sodic amphibole, phengite, paragonite, clinozoisite, epidote, chlorite, albite, accessory titanite and ilmenite. Eclogites are predominantly composed of garnet, omphacite, sodic–calcic amphibole, clinozoisite, phengite, paragonite, quartz with accessory minerals such as rutile, titanite, ilmenite, calcite and apatite. Garnet in eclogite has a composition of 53–79 mol% almandine, 8.5–30 mol% grossular, 5–24 mol% pyrope and 0.6–13 mol% spessartine. Garnet in blueschists shows similar composition. Sodic amphiboles include glaucophane, ferro‐glaucophane and crossite, whereas the sodic–calcic amphiboles mainly comprise barroisite and winchite. The jadeite content of omphacite varies from 35–54 mol%. Peak eclogite facies temperatures are estimated as 480–580 °C for a pressure range of 14–21 kbar. The conditions of pre‐peak, epidote–blueschist facies metamorphism are estimated to be 350–450 °C and 8–12 kbar. All rock types have experienced a clockwise P–T path through pre‐peak lawsonite/epidote‐blueschist to eclogite facies conditions. The retrograde part of the P–T path is represented by the transition of epidote‐blueschist to greenschist facies conditions. The P–T path indicates that the high‐pressure rocks formed in a B‐type subduction zone along the northern margin of the Palaeozoic South Tianshan ocean between the Tarim and Yili‐central Tianshan plates.

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Section: Metamorphic Evolution Of Hp–lt Rockssupporting

confidence: 62%

Section: Metamorphic Evolution Of Hp–lt Rocksmentioning

confidence: 99%

P–T path of high‐pressure/low‐temperature rocks and tectonic implications in the western Tianshan Mountains, NW China

Gao

Klemd

Zhang

et al. 1999

Journal Metamorphic Geology

172

141

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“…Messiga et al. , 1989; Hoogerduijn Strating, 1991; Messiga & Scambelluri, 1991; Brouwer et al. , 2002), whereas quantitative data on the prograde trajectory have not yet been proposed.…”

Section: Geological Settingmentioning

confidence: 99%

“…, 2002), whereas quantitative data on the prograde trajectory have not yet been proposed. Nevertheless, it is commonly assumed, based on the occurrence of crossite + paragonite + epidote inclusions in garnet and by omphacite + epidote aggregates as pseudomorphs after lawsonite (Messiga & Scambelluri, 1991; Brouwer et al. , 2002), that the prograde path towards the eclogitic peak traversed the blueschist facies.…”

Section: Geological Settingmentioning

confidence: 99%

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A counter‐clockwise P–T path for the Voltri Massif eclogites (Ligurian Alps, Italy)

Vignaroli

Rossetti

Bouybaouène

et al. 2005

Journal Metamorphic Geology

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Integrated petrological and structural investigations of eclogites from the eclogite zone of the Voltri Massif (Ligurian Alps) have been used to reconstruct a complete Alpine P-T deformation path from burial by subduction to subsequent exhumation. The early metamorphic evolution of the eclogites has been unravelled by correlating garnet zonation trends with the chemical variations in inclusions found in the different garnet domains. Garnet in massive eclogites displays typical growth zoning, whereas garnet in foliated eclogites shows rim-ward resorption, likely related to re-equilibration during retrogressive evolution. Garnet inclusions are distinctly different from core to rim, consisting primarily of Ca-, Na/Ca-amphibole, epidote, paragonite and talc in garnet cores and of clinopyroxene ± talc in the outer garnet domains. Quantitative thermobarometry on the inclusion assemblages in the garnet cores defines an initial greenschist-to-amphibolite facies metamorphic stage (M1 stage) at c. 450-500°C and 5-8 kbar. Coexistence of omphacite + talc + katophorite inclusion assemblage in the outer garnet domains indicate c. 550°C and 20 kbar, conditions which were considered as minimum P-T estimates for the M2 eclogitic stage. The early phase of retrograde reactions is polyphase and equilibrated under epidote-blueschist facies (M3 stage), characterized by the development of composite reaction textures (garnet necklaces and fluid-assisted Na-amphibole-bearing symplectites) produced at the expense of the primary M2 garnet-clinopyroxene assemblage. The blueschist retrogression is contemporaneous with the development of a penetrative deformation (D3) that resulted in a non-coaxial fabric, with dominant topto-the-N sense of shear during rock exhumation. All of that is overprinted by a texturally late amphibolite/greenschist facies assemblages (M4 & M5 stages), which are not associated with a penetrative structural fabric. The combined P-T deformation data are consistent with an overall counter-clockwise path, from the greenschist/amphibolite, through the eclogite, the blueschist to the greenschist facies. These new results provide insights into the dynamic evolution of the Tertiary oceanic subduction processes leading to the building up of the Alpine orogen and the mechanisms involved in the exhumation of its high-pressure roots.

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Fault‐slip analysis in the metaophiolites of the Voltri Massif: constraints for the tectonic evolution at the Alps/Apennine boundary

et al. 2008

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The metaophiolitic Voltri Massif underwent a complex tectono-metamorphic evolution, resulting from subduction to collision events during the Alpine orogenic cycle, and was subsequently involved in the first stages of the Apennine Orogeny. So this is a key area to investigate the late orogenic Alpine tectonics and its time relationship with the first Apenninic deformation events.We performed detailed mapping, fault-slip analysis and study of fault rocks in a study area located at the eastern border of the Voltri Massif. Here we recognized two main generations of reverse shear zones (RSZ). The first one (RSZ1) is associated to mylonites and protomylonites in greenschist to low-greenschist metamorphic facies and is characterized by a ductile to ductilebrittle behaviour; RSZ1 display either top-to-N-NW or to-SW kinematics. The second generation of reverse shear zones (RSZ2) is characterized by fault breccia, crush breccia or protocataclasite; RSZ2 sense of tectonic transport ranges from top-to-NW, -SW and -NE.RSZ1 structures are locally folded by 10 m-scale, open chevron folds with fold axes gently plunging to SW that likely represent the last phases of deformation during Alpine collision.RSZ2 structures locally reactivate RSZ1, with a more brittle behaviour and produce a huge volume of fault rock. They are coeval with low-greenschist to zeolite-facies metamorphic conditions. The RSZ2 fit a transpressional regime active at the eastern border of the Voltri Massif at least during the late Oligocene-early Miocene.

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Retrograde P‐T‐t path for the Voltri Massif eclogites (Ligurian Alps, Italy): some tectonic implications

Cited by 63 publications

References 43 publications

P–T path of high‐pressure/low‐temperature rocks and tectonic implications in the western Tianshan Mountains, NW China

P–T path of high‐pressure/low‐temperature rocks and tectonic implications in the western Tianshan Mountains, NW China

A counter‐clockwise P–T path for the Voltri Massif eclogites (Ligurian Alps, Italy)

Fault‐slip analysis in the metaophiolites of the Voltri Massif: constraints for the tectonic evolution at the Alps/Apennine boundary

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