for peer review only - arpi.unipi.it · 3 giovanni musumeci1, maria elena spano 2, gian piero...

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Geological map of Monte Grighini Variscan basement

(Sardinia, Italy)

Journal: Journal of Maps

Manuscript ID: Draft

Manuscript Type: Original Article

Date Submitted by the Author: n/a

Complete List of Authors: Musumeci, Giovanni; Università di Pisa, Scienze della Terra Spano, Maria; Università di Cagliari, Dipartimento di Scienze della Terra Cherchi, Gian Piero; ARPAS, Dipartimento Provinciale di Sassari Franceschelli, Marcello; Università di Cagliari, Dipartimento di Scienze della Terra Pertusati, Pier Carlo; Università di Pisa, Dipartimento di Scienze della Terra Cruciani, Gabriele; Università di Cagliari, Dipartimento di Scienze della Terra

Keywords: Variscan basement, metamorphic units, stryke-slip shear zone, synkinematic magmatism, Sardinia

URL: http://mc.manuscriptcentral.com/tjom

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GEOLOGICAL MAP OF MONTE GRIGHINI VARISCAN BASEMENT 1

(SARDINIA, ITALY) 2

Giovanni Musumeci1, Maria Elena Spano

2, Gian Piero Cherchi

3, Marcello Franceschelli

2, Pier 3

Carlo Pertusati1, Gabriele Cruciani

2 4

1Dipartimento di Scienze della Terra, Università di Pisa, Via S. Maria 53, 56126 Pisa Italy. 5

2Dipartimento di Scienze della Terra, Università di Cagliari, Via Trentino 51, Cagliari, Italy. 6

3ARPAS Dipartimento Provinciale di Sassari, Via Rockfeller, 58-60, Sassari. 7

8

Abstract 9

The study area belongs to the Nappe zone of the Sardinian Variscan basement in the NW part 10

of the Flumendosa Antiform. The area shows a section of the Variscan orogen in Sardinia 11

with three tectonic units stacked and folded during the Middle Carboniferous Variscan 12

tectonics under lower greenschist nd upper amphibolites facies conditions, 13

successively juxtaposed during late Variscan tectonics. The presented 1:25,000 scale 14

geological map, the cross sections and the shear zone deformation map illustrate the tectonic 15

and metamorphic setting of the area, resulting from the polyphasic Variscan collisional 16

evolution including early nappe stacking and following strike slip and extensional tectonics 17

coeval with a late Carboniferous magmatism. 18

19

20

21

22

23

Corresponding author: G. Musumeci, email. [email protected] 24

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1. Introduction 27

The Monte Grighini complex is located in the Nappe zone of the Variscan metamorphic 28

basement of Sardinia (Fig. 1), which is a part of the Southern Variscan realm (Carmignani et 29

al., 1994). In the Nappe zone all of the tectonic units are emplaced with a top-to-the-south 30

transport direction (Conti et al., 2001); metamorphism and internal deformation of rocks 31

increase northward from subgreenschist in the south, up to amphibolite facies in the internal 32

Nappe zone (Franceschelli et al. 1990; Elter et al. 1986). The inner zone of the chain, north of 33

Posada-Asinara line, is characterized by widespread occurrence of migmatite (Cruciani et al. 34

2008a,b) with subordinate eclogite and granulite (Franceschelli et al. 2002, 2007). 35

The Monte Grighini complex (Fig. 2) was firstly considered a basement of pre-Variscan age 36

(Carmignani et al., 1982) on the basis of occurrence of metamorphic rocks of amphibolites 37

facies. Successively detailed field survey coupled with structural and petrological studies 38

allow to reinterpret the Monte Grighini complex as a Variscan basement marked by the 39

occurrence of (i) the deepest unit of the Nappe zone and (ii) a major late Variscan strike-slip 40

shear zone (Elter et al. 1990) exploited by metaluminous (diorite to monzogranite) and 41

peraluminous (leucogranite) synkinematic intrusions (Cherchi and Musumeci 1986; 42

Musumeci 1992). 43

The aim of this map is to give new and updated information about the lithological, structural 44

and metamorphic setting of the Variscan basement in the Nappe zone of central Sardinia. 45

46

2. Methods 47

The map at 1:25,000 scale covers an area of nearly 60 km2 that was originally mapped at the 48

1:10,000 scale. Both the original data and map are represented on a vector topographic map 49

(Carta Tecnica Regionale – Regione Autonoma della Sardegna) and stored in a GIS database 50

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(Coordinate System Monte Mario Gauss Boaga ovest). The overall dataset includes i) 51

lithological, structural and petrographic data collected in two master theses (Cherchi 1985, 52

Musumeci 1985) and PhD thesis (Musumeci 1991a), together with ii) new geo-petrographic 53

data (M.E. Spano PhD thesis, in progress). During the first field survey a wide ductile shear 54

zone (Monte Grighini Shear Zone) and synkinematic intrusions were recognized for the first 55

time in the Variscan basement of Sardinia and described in Cherchi and Musumeci (1986), 56

Carmignani et al. (1987) and Elter et al. (1990). Structural data interpretation is based on 57

geometrical analysis (equal-area lower-hemisphere stereographic projections) of the main 58

foliation (S1 and S2) in the tectonic units and mylonitic and cataclastic foliation in the shear 59

zone that allow to calculate the shear strain variation and the amount of ductile displacement 60

(Musumeci 1991b; 1992) 61

62

Lithostratigraphy 63

The Variscan basement in the study area consists of three tectonic units with lower 64

greenschist to upper amphibolites facies metamorphism and late Carboniferous intrusive 65

rocks. From bottom to top they are: Monte Grighini Unit, Castello Medusa Unit and Gerrei 66

Unit. 67

Gerrei Unit: Middle Ordovician to Siluro–Devonian very low metamorphic grade 68

lithostratigraphic succession that starts with the Middle Ordovician metavolcanics 69

(Carmignani et al 1994) that consists of metavolcanite of intermediate composition (Monte 70

Santa Vittoria Fm.) upward followed by metasandstone and metarkoses (Su Muzzioni Fm.) 71

and rhyolitic-rhyodacitic metavolcanics (Porfiroidi Fm.). The Upper Ordovician-Silurian 72

succession starts with metarkoses and quartzites (Genna Mesa Fm.) followed by metapelites 73

with fossiliferous metasiltites (crynoids articles and inarticulated brachiopods) with thick 74

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fossiliferous (encrinite) metalimestone (Rio Canoni Fm.). Black shales with decametre thick 75

lenticular bodies of nodular limestone correspond to the Siluro-Devonian succession (Scisti 76

Neri Fm. ). 77

Castello Medusa Unit: low metamorphic grade (biotite zone, upper greenschist facies) 78

metarkoses related to the Upper Ordovician volcanoclastic succession of Genna Mesa Fm., 79

upward followed by metapelites with intercalated decameter thick marble and calc-schist 80

belonging to the Sa Lilla Fm. of Upper Silurian-Devonian age. 81

Monte Grighini Unit: metavolcanic-volcanoclastic (Truzzulla Fm.) and metasedimentary 82

(Toccori Fm.) rocks of medium metamorphic grade (Figs 3a, b, c) intruded by late 83

Carboniferous granitoids (Figs 3d, e, f). The metamorphic grade increases from the biotite-84

garnet zone at east-southeast to the sillimanite zone at west-northwest. Common mineral 85

assemblages are (i) muscovite + biotite + garnet, (ii) muscovite + biotite + garnet + staurolite 86

+ oligoclase, (iii) biotite + andalusite + plagioclase + K-feldspar, (iv) biotite + staurolite + 87

andalusite + plagioclase + K-feldspar + fibrolite (Musumeci 1992). 88

The Truzzulla Fm. consists of Upper Ordovician (447 ± 4.3 Ma) acidic metavolcanics, 89

metarkose and arkosic metasandstones of calc-alkaline affinity (Cruciani et al. 2013). 90

Metavolcanics are upward followed by metarkoses and arkosic metasandstones with augen 91

textures partitioned in intensely foliated domains (Fig. 3b). 92

The Toccori Fm. consists of metapelite with intercalated centimeter to decimeter-thick 93

metasiltite layers. White quartzite levels (Fig. 3c) marks the base of the Toccori Fm., while 94

black graphitic metapelite and meter-thick marble lenses occur in the uppermost portion of 95

the formation. The garnet + staurolite + biotite + K-white mica + plagioclase mineral 96

assemblage of the Toccori Fm. (Fig. 3a) is interpreted as the result of medium metamorphic 97

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grade conditions developed in the deepest portion of external nappes during the main phase of 98

folding and south verging nappe stacking (Musumeci 1992). 99

100

Monte Grighini Intrusive complex 101

Late Variscan intrusive rocks and dyke system (305-295 Ma) constitute the Monte Grighini 102

intrusive complex emplaced in the Monte Grighini Unit. On the basis of mineral assemblages 103

and geochemical signature (Del Moro et al. 1991), a diorite, tonalite, monzogranite suite ( I-104

type calc-alkaline metaluminuos suite) and a leucogranite (S-type peraluminous suite) have 105

been distinguished. 106

Monte Grighini Diorite: fine-grained biotite-bearing diorite occur as metre to decametre thick 107

bodies and as centimetre to decimetre thick enclaves within tonalites and monzogranites (Fig. 108

3d, e). The largest bodies of diorites crop out at north and northwest of Monte Grighini top. 109

Monte Grighini Tonalite: biotite-bearing medium to fine grained tonalites are two NW-SE 110

elongated sheet bodies. Fabric marked by alignment of igneous plagioclase and biotite 111

characterizes the tonalite body emplaced within the Toccori Fm. at east of Cuccuru Mannu. 112

Monte Grighini Monzogranite: medium-grained biotite monzogranite (Fig. 3d, e), forms a 113

wide NW-SE elongated sheet intrusion exposed in the central and northern portion of the 114

massif, that extends eastward at shallow depth within the Monte Grighini Unit. 115

Monte Grighini Leucogranite: fine-grained muscovite-bearing leucogranite (Fig. 3e, f) forms 116

a NW-SE elongated sheet intrusion. Mineral assemblages are (i) quartz + K-feldspar + 117

plagioclase + K-white mica + biotite ± garnet and (ii) quartz + K-feldspar + plagioclase + K-118

white mica +garnet ± biotite. K-white mica -bearing assemblage dominates in the southern 119

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portion (Su Cruccuri-Monte Corongiarbu) while K-white mica - and biotite-bearing 120

assemblages occur in the northern portion (Cuccuru Mannu). 121

Dyke system consists of aplitic dykes related to intrusive complex and quartz dykes that are 122

very abundant and cross-cutting lithological contacts and tectonic structures including the 123

shear zone. Dykes strike mainly along ENE-WSW and NW-SE directions, orthogonal and 124

parallel to the shear zone, respectively. 125

126

Tectonic and metamorphic evolution 127

The tectonic units experienced a polyphase Variscan tectonic and metamorphic evolution 128

characterized by an early shortening deformation related to the syn-collisional southward 129

nappe stacking (D1 phase Gerrei Unit and D1-D2 phases Castello Medusa and Monte Grighini 130

Unit) with isoclinal folds overturned towards southwest and axial plane foliation (F1 - S1 131

Gerrei Unit and F2 -S2 Castello Medusa and Monte Grighini Unit; Fig. 4a). Deformation 132

developed under lower greenschist facies (chlorite zone) in the Gerrei Unit while Castello 133

Medusa and Monte Grighini units experienced syn-D2 upper greenschist facies (biotite zone) 134

and amphibolite (garnet – staurolite zone) facies metamorphism, respectively (Fig. 5a). In the 135

Monte Grighini Unit upper amphibolite facies P-T conditions are testified by syn-post D2 136

growth of andalusite and sillimanite/fibrolite and cordierite assemblage (Fig. 5b). Recent 137

geothermobarometric data (Spano et al. 2012), indicate P-T condition of 7,5 kbar - 500°C for 138

syn-D2 and 4 kbar –for post-D2 amphibolite facies metamorphism. Nappe-stacking structures 139

were deformed by successive deformation phase (D2 Gerrei Unit and D3 Castello Medusa and 140

Monte Grighini Unit; Fig. 5c) with development of large scale NW-SE trending upright 141

antiform and synform (F2 Gerrei Unit and F3 Castello Medusa Unit and Monte Grighini Unit). 142

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Late Variscan shear zone: NW-SE trending kilometer-wide dextral strike-slip shear zone 143

marked by the synkinematic emplacement of the intrusive complex represents the main 144

tectonic lineament of the Monte Grighini complex (Musumeci 1992). Shear deformation 145

increases toward west from protomylonite zone to ultramylonite zone forming a narrow belt 146

along the western side of shear zone (Figs, 4b, c). At mesoscopic scale, mylonite fabrics are 147

NW-SE trending C-type shear bands and mylonitic-ultramylonite foliation that steeply dip 148

toward southwest and bear subhorizontal to gently plunging mineral lineations (Figs 4e, f and 149

Figs 5d,e,f). The C-type shear bands are homogeneously distributed throughout shear zone, 150

while consistently with the westward increase of shear strain , the ultramylonite foliation are 151

partitioned in the ultramylonite zone where the highest value of shear strain are attained 152

(Musumeci 1991b). The westernmost and southernmost portions of the shear zone correspond 153

to a west dipping zone of cataclastic rocks of variable thickness (decametre to hectometre), 154

marked by brittle deformation. Southwest dipping cataclastic foliation and shear planes show 155

a top to the southwest sense of shear (Fig. 4d). 156

Conclusions 157

A detailed field survey, including geological mapping, petrographic/petrologic investigations 158

and systematic structural analyses allowed the depiction of a 1:25,000 scale geological map of 159

the Monte Grighini complex that gives new insights about the Ordovician magmatism and the 160

composite stack of Variscan units in the north-western sector of Sardinia Nappe zone. 161

Specifically, detailed geological mapping has allowed us to pursue the following main topics: 162

- compilation of a synthesis of both existing and new data about the lithological, structural 163

and petrological features that characterize the metamorphic and igneous units of the mapped 164

area; 165

- detailed mapping of late Variscan shear zone and synkinematic intrusions; 166

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- the role of late Variscan strike-slip and extensional tectonics in the final architecture of the 167

chain. 168

The new and updated geological information about the Monte Grighini complex may be the 169

base for further studies on the tectono-metamorphic evolution and geodynamic setting of 170

Paleozoic basement in Sardinia. 171

172

173

Software 174

The map database was built using ArcGIS software with the final map layout assembled using 175

CorelDRAW X5 graphics suite. Topographic maps of Carta Tecnica Regionale of the 176

Regione Autonoma della Sardegna were downloaded from www.sardegnaterritorio.it. Photos 177

were managed and compiled with CorelDRAW X5 graphics suite. 178

179

Acknowledgements 180

M.E.Spano gratefully acknowledges the Sardinia Regional Government for the financial 181

support to her PhD scholarship (P. O. R. Sardegna F. S. E. Operational Programme of the 182

Autonomous Region of Sardinia, European Social Found 2007–2013—Axis IV Human 183

Resources, Objective l.3, Line of Activity l.3.1.). Financial support from Università degli 184

Studi di Cagliari and Università degli Studi di Pisa is acknowledged. The authors wish to 185

thank the Ente Foreste of the Regione Autonoma della Sardegna for hospitality during the 186

field work. 187

188

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Map Design 189

The topographic map has been done through the following steps: i) cartographic base was 190

imported in ArcGIS software, ii) then it was edited: contour lines directives (every 50 m) has 191

been stained by black color whereas the contour lines every 10 meters are grey, iii) few listed 192

spots are reported at the top of the hills, iv) roads are brown and rivers are blue, v) few 193

toponyms are reported. Coordinate grid is related to UTM (Universal Transversal Mercator - 194

Zone 32S – European Datum 1950) coordinate system and Gauss Boaga (West– Rome 1940) 195

and latitude /longitude system are also reported. 196

197

References 198

Carmignani L, Oggiano G, Barca S, Conti P, Eltrudis A, Funedda A, Pasci S, Salvadori I 199

(2001) Geologia della Sardegna. Note illustrative della Carta Geologica della Sardegna in 200

scala 1:200,000. Memorie descrittive della Carta Geologica d’Italia LX, p 283. 201

Carmignani L., Carosi R., Di Pisa A., Gattiglio G., Musumeci G., Oggiano G., & Pertusati 202

P.C. (1994). The Hercynian chain in Sardinia (Italy). Geodinamica Acta, 7, 1, 31-47. 203

Carmignani, L., Cherchi, G.P, Del Moro, A., Franceschelli, M., Ghezzo, C., Musumeci, G., 204

& Pertusati, P.C. (1987). The mylonitic granitoids and tectonic Units of the Monte 205

Grighini Complex (Western-Central Sardinia): A preliminary note. In: Sassi F., Bourrouilh 206

R., (eds) IGCP Project N° 5. Correlation of Variscan and Pre-variscan events of the 207

Alpine-Mediterranean Mountain belt. Newsletter, 7, 25-26. 208

Carmignani, L., Cocozza, T., Ghezzo, C., Pertusati, P.C., & Ricci, C.A. (1982). I lineamenti 209

del Basamento Sardo. Guida alla Geologia del Paleozoico sardo. Guide Geologiche 210

Regionali. Memorie della Società Geologica Italiana, 20, 11-23. 211

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Carmignani, L., Oggiano, G., Barca, S., Conti, P., Salvadori, I., Eltrudis, A., Funedda, A., & 212

Pasci, S. (2001). Geologia della Sardegna; Note Illustrative della Carta Geologica della 213

Sardegna in scala 1:200.000, Memorie Descrittive della Carta Geologica d’Italia, vol. 60, 214

Servizio Geologico d’Italia, Roma, 283 pp. 215

Cherchi, G.P. (1985). Il granito del Monte Grighini studio meso e microstrutturale. 216

Unpublished MSc Thesis, Università di Pisa, Dipartimento di Scienze della Terra. 217

Cherchi, G.P., & Musumeci, G. (1987). Il leucogranito del M. Grighini (Sardegna centro-218

occidentale), un esempio di granito deformato all'interno di una fascia di taglio duttile: 219

caratteristiche meso e microstrutturali. Atti Società Toscana di Scienze Naturali, Memorie, 220

(1986), Serie A, XCIII, 13-29. 221

Conti, P., Carmignani, L. and Funedda, A. (2001). Change of nappe transport direction during 222

the Variscan collisional evolution of central-southern Sardinia (Italy), Tectonophysics, 223

332, 255–273. 224

Cruciani, G., Franceschelli, M., Musumeci, G., Spano, M.E., & Tiepolo, M. (2013). U–Pb 225

zircon dating and nature of metavolcanics and metarkoses from the Monte Grighini Unit: 226

new insights on Late Ordovician magmatism in the Variscan belt in Sardinia, Italy. 227

International Journal of Earth Sciences, 102, 2077–2096. 228

Del Moro, A., Laurenzi, M., Musumeci, G., & Pardini, G. (1991). Rb/Sr and Ar/Ar 229

chronology of Hercynian Mt. Grighini intrusive and metamorphic rocks, (central-western 230

Sardinia). Plinius, 4, 121-122. 231

Elter, F.M., Franceschelli, M., Ghezzo, C., Memmi, I., & Ricci, C.A. (1986). The geology of 232

northern Sardinia. In: Carmignani L., Cocozza T., Ghezzo C., Pertusati P.C., Ricci C.A., 233

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(Eds.) Guide-book to the excursion on the paleozoic basement of Sardinia. IGCP Project 234

No. 5, Newsletter, special issue, 87-102. 235

Elter, F.M., Musumeci, G., & Pertusati, P.C. (1990). Late Hercynian shear zones in Sardinia. 236

Tectonophysics, 176, 387- 404. 237

Franceschelli, M., Carcangiu, G., Caredda, A.M., Cruciani, G., Memmi, I., & Zucca, M. 238

(2002). Transformation of cumulate mafic rocks to granulite and re-equilibration in 239

amphibolite and greenschist facies in NE Sardinia, Italy. Lithos, 63, 1-18. 240

Franceschelli, M., Pannuti, F., & Puxeddu, M. (1990). Texture development and PT time path 241

of psammitic schists from the Hercynian chain of NW Sardinia (Italy). European Journal 242

of Mineralogy, 2, 385 – 398. 243

Franceschelli, M., Puxeddu, M., Cruciani, G., & Utzeri, D. (2007). Metabasites with eclogite 244

facies relics from Variscides in Sardinia, Italy: a review. International Journal of Earth 245

Sciences, 96, 795–815. 246

Musumeci, G. (1985). Monte Grighini: evoluzione tettonico-metamorfica di un edificio a 247

falde di ricoprimento erciniche. Unpublished MSc Thesis, Università di Pisa, Dipartimento 248

di Scienze della Terra. 249

Musumeci, G. (1991a). Tettonica trascorrente, magmatismo e metamorfismo nel basamento 250

ercinico sardo: Il Complesso del Monte Grighini (Sardegna centro-occidentale). Università 251

di Pisa, PhD Thesis, Dipartimento di Scienze della Terra. 252

Musumeci, G. (1991b). Displacement calculation in a ductile shear zone: Monte Grighini 253

shear zone (Central-Western Sardinia). Bollettino della Società Geologica Italiana, 110, 254

771-777. 255

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Musumeci, G. (1992). Ductile wrench tectonics and exhumation of hercynian metamorphic 256

basement in Sardinia: Monte Grighini Complex. Geodinamica Acta, 5, 1-2, 119-133. 257

Spano, M.E., Cruciani, G., Franceschelli, M., Massonne, H.-J., & Musumeci, G. (2012). 258

Variscan metamorphic evolution of the Monte Grighini Unit in central Sardinia. Gèologie 259

de la France, 1, 204-205. 260

261

Figure captions 262

Figure 1. Tectonic map of the Variscan basement of Sardinia (after Carmignani et al., 2001, 263

modified). 264

Figure 2. Tectonic sketch map of Monte Grighini complex. 265

Figure. 3. (a) staurolite-garnet-bearing micaschist of Toccori Fm.; (b) metavolcanic 266

sandstone of Truzzulla Fm with augen fabric; (c) white quartzite at the base of Toccori Fm; 267

(d) intrusive contact between diorite (MGd) and monzogranite (MGm). Scale bar: 30 cm; (e) 268

monzogranite (MGm) with diorite enclaves (MGd), cross cut by muscovite –bearing 269

leucogranite (MGl); (f) muscovite-bearing leucogranite. Red dots are Fe-oxides. 270

271

Figure. 4. (a) F2 isoclinal folds in micaschist. Scale bar: 12 cm; (b) ultramylonite-phyllonite 272

rocks at the western boundary of the shear zone; (c) outcrop scale view of mylonite-273

ultramylonite transition. Scale bar: 20 cm; (d) cataclastic zone, detail of southwest dipping 274

cataclastic foliation enveloping leucogranite dykes; (e) muscovite-bearing mylonitic 275

leucogranite with C/S fabric. Scale bar: 3 cm; (f) ultramylonite fabric in sheared 276

monzogranite marked by quartz ribbons and K-feldspar porphyroclasts. Scale bar: 1cm. 277

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Figure. 5 (a) Toccori micaschist, syntectonic garnet porphyroblast in a fine- to medium- 279

grained quartz and phillosilicate-rich layered matrix; (b) millimetric mica fish of potassic 280

white mica with growth of fibrolitic sillimanite in a fine -grained quartz and fibrolite matrix; 281

(c) F3 microfold deforming S2 foliation; (d) C/S fabric in mylonitic K-white mica bearing 282

leucogranite. Scale bar: 1 mm; (e) ultramylonite fabric in strongly sheared monzogranite 283

marked by quartz ribbons with K-feldspar porphyroclasts; (f) phyllonite fabric in the most 284

deformed domain of the ultramylonite zone. 285

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Figure 1 289

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Figure 2 297

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Figure 3 306

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Journal of Maps

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For Peer Review Only

Geological map of Monte Grighini Variscan basement (Sardinia, Italy)(1) (2) (3) (2) (2)G.Musumeci , M.E.Spano , G.P.Cherchi , M.Franceschelli , G.Cruciani(1), P.C.Pertusati

(1) Dipartimento Scienze della Terra, Università di Pisa (2) Dipartimento Scienze Chimiche e Geologiche, Università di Cagliari (3) ARPAS, Dipartimento provinciale di Sassari

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GERREI UNIT SHEAR ZONE MONTE GRIGHINI UNIT

Toccori

Cuccuru Mannu

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200

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400

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200

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400

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M.E.Spano gratefully acknowledges the Sardinia Regional Government for the financial support to her PhD scholarship (P. O. R. Sardegna F. S. E. Operational Programme of the Autonomous Region of Sardinia, European Social Found 2007–2013—Axis IV Human Resources, Objective l.3, Line of Activity l.3.1.).

The authors wish to thank the Ente Foreste della Regione Autonoma della Sardegna for hospitality during the field work.

Financial support from Università degli Studi di Cagliari and Università degli Studi di Pisa is aknowledged.

Topographic map from the 1.10.000 C.T.R. (Carte Tecniche Regionali) maps - Regione Autonoma della Sardegna.

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#0

401.43

393.11

357.85

299.03

344.14

332.80

348.06

283.08

274.95

265.80

264.09

359.21

304.53

307.83

340.76

310.40

328.84

346.30

333.10 334.86

322.59

337.41

354.56

354.41

362.79

383.70

384.62

373.37

377.06

388.97

417.80

425.94

278.16

337.56

334.35

351.51 305.36

314.75

305.42

213.54

234.77

208.25

226.60

234.10

251.83

245.95

286.51

266.90

269.52

283.54

289.78

298.21

289.09

321.17

312.74

281.34

288.08

308.49

338.88

312.84

304.86312.57

314.44321.83

332.69

334.95

344.70353.13

325.85

343.51

343.00

355.35

350.13

358.56

453.45

440.25

332.19

284.83

276.58

275.23

273.97

197.38

174.32

171.65

213.57

198.78

194.05

177.10

160.20

162.10

154.66

158.22

152.96

166.23

137.65

136.75

126.39

125.73

105.48

84.82

101.29

81.56

167.15

200.72

183.68

194.87

218.69

206.27

265.96

233.05

251.11

284.56

284.98

295.10356.95

355.51

376.99

259.03

272.88

191.16

167.17

306.00

299.10

294.92

278.00

264.41

208.12

310.27

332.42409.21

389.68

351.66

356.76

391.47

285.87

283.86

316.59

114.07

112.25

205.61

121.69

310.43

311.69

183.89

184.65

183.77

129.49

107.8588.39

118.55

103.61

92.95

300.78

311.53

336.92

235.68

343.36

371.17

399.05

415.11

400.63

417.74

433.36

432.07

539.69

552.97

577.44

574.42

614.26

647.95

622.48

649.28

670.22

663.02

669.74

250.58

215.71

170.62

167.45

134.89

84.94

268.51

139.23129.17

150.69

257.99

173.87

128.81

174.63

170.59

142.87 226.22

176.80

214.12

206.40

216.66

209.14204.68

273.20

264.94

200.28

180.44

218.38

184.69

211.25

216.59

240.17

235.03

251.17

272.54

270.45

270.99

270.25

288.18

214.69

84.94

234.10

309.06

313.16

251.19

327.40

312.46

285.10

284.29

155.07

132.42

137.46

116.14

209.45

157.26

85.67

46.17

91.29

73.51

91.09

144.20

150.48

117.36

209.07

252.23

236.57

373.99

140.69

146.48

143.86

42.77

305.08

202.22

662.72

208.47

235.14

244.95

206.61

296.25

404.93

319.52

275.11

356.15

403.19

401.57

382.54

425.01

280.24

244.59

215.61

274.05

232.41

272.19 270.39

407.14

467.60

460.42

472.89434.37

307.71

415.89

401.49

148.40

185.21

184.88

266.95

216.94

233.50

227.45

240.81

244.32

253.21

273.32

271.85

280.19276.59

225.54

238.08

264.32

283.12

270.42

303.12

296.91

297.27

270.90

293.66

281.57

290.27

387.60

376.89

365.73

349.54386.90

355.79

265.01

302.89

306.91

366.84

370.96

346.75

496.84

492.70

533.18

126.71

344.06

370.99

380.59

382.52

378.26

403.01

385.56

437.07

512.40

617.12

300

250

350

200

400

450

350

300

300

350

300

300

350

350

300

200

250

350

300

300

250

350

300

350

250

350

250

250

300

300

350

400

150

100

200

250

300

250

250

200

150 200

100

200

200

150

200

300

250

200

250

250

250

150

sa Grutta Saua Madri

Br.cu Fogaies

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CUCCURUE’UAS

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SERRA CANNA

Allai

200

250

350

150

100

400

450

500

550

600

300

650

50

150

650

200

200

350

150

400

150

100

350

350

100

100

150

350

400

100

350

100

200

150

250

150

400

250

100

100

100

150

300

300

150

150

600

350

400

100

50

400

250

150

200

450

300

350

500

550

250

300

200

200

100

600

150

150

400

250

350

100

200

100

350

250200

250

200

100

250

250

450

200

400

300

250

400

350

250

400

350

450

300

350

150

400

150

200

350

250

350

200

150

300

250

200

350

400

350

150

150

81 000 m E14 8214 8314 8414 85148614

87148814 8914 9014

8114 8214 8314 8414 85148614

87148814 8914 9014

2544

2444

2344

2244

2144

2044

1944

1844

1744

1644

1544

1444

13 000 m N44

2544

2444

2344

2244

2144

2044

1944

1844

1744

1644

1544

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#

GIOSTRIS

81 000mE4

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1844

1744

1644

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13 000mN44 13 44

2444

2544

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1844

1744

1644

1544

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2444

2544

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4 854

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4 88489

490

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81 000 m E4 82

483

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904

M.FILIGHI

39°51 41’’’

39°57 00’’’39°57 00’’’

39°54 00’’’39°54 00’’’

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0’’

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East from Greenwich - UTM (Universal Transverse Mercator) Grid, Zone 32S (ED50) - Roma 1940 - Gauss Boaga Ovest

Shear zone Monte Grighini Unit

1.3 %

2.7 %

4.0 %

5.3 %

6.7 %

8.0 %

9.3 %

10.7 %

12.0 %

2.2 %

4.3 %

6.5 %

8.7 %

10.9 %

13.0 %

15.2 %

17.4 %

19.6 %

3.6 %

7.1 %

10.7 %

14.3 %

17.9 %

21.4 %

S foliation2 n=150

mineral lineation

n=80

F fold axis2 n=80

1.4 %

4.3 %

7.2 %

10.1 %

13.0 %

15.9 %

18.8 %

F fold axis3 n=70

Gerrei Unit

1.8 %

3.6 %

5.5 %

7.3 %

9.1 %

10.9 %

12.7 %

14.5 %

16.4 %

1.4 %

2.9 %

5.7 %

8.6 %

10.0 %

12.9 %

15.7 %

18.6 %

S foliation1 n=110

F -F fold axis1 2 n=80

0.8 %

3.0 %

6.8 %

10.6 %

15.2 %

20.5 %

25.0 %

30.3 %

1.5 %

3.8 %

5.3 %

7.6 %

10.6 %

15.2 %

20.5 %

25.0 %

29.5 %

2.6 %

5.3 %

10.5 %

15.8 %

21.1 %

26.3 %

S-plane n=132

C-plane n=132

minerallineation

n=75

ACN

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MSV

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3040

45

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55

60

40

45

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15

70

45

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55

50

50

25

50

60

70

80

80

80 75

7080

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65

80

25

75

85

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20 70

15

80

60

80

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25

8570

70

75

25

70

65

80

75

2070

80

70

15

80

75

85

50

60

80

10

70

8085

80

75

80

75

75

25

80

50

65

15

15

12

60

15

20

18

40

35

60

20

35

15

20

35

20

15

75

80

50

50

40

60

60

40

15

22

50

55

15

30

60

10

12

55

15

60

35

50

20

30

35

50

15

65

40

6540

35

40

45

40

30

45

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80

8075

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1027

80

7075

75

25

45

45

50

60

45

40

45

40

25

15

30

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15

40

30

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30

45

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50

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15

30

10

45

60

75

40

10

45

25

40

20

55

50

60

35

25

50

40

40

45

5040

30

20

10

30

35

20

35

40

60

40

35

60

45

25

10

15

30

35

25

30

35

35

3525

20

20

30

10

55

45

30

75

80

70

40

25

3510

50

50

65

15

20

55

12

10

45

30

30

5045

40

55

10

15

50

65

65 65

70

65

80

20

4580

70

75

15

50

12

7075

45

45

30

40

25

10

15

25

75

10

70

75 60

70

80

55

55

18

40

80

70

20

0 250 500 750 1km

0 250 500 750 1250 1500 17501Km 2km

Scale 1:25.000

N

a

a

b

GEOLOGICAL LEGEND:

Q - Quaternary deposits

Qd - Quartz dykes

Cz - Cataclasite zone

MGl - Monte Grighini Leucogranite

SGA - ‘Scisti Neri’ Formation

CSA - Complesso di Sa Lilla

TC - Toccori Formation

PRF - ‘Porfiroidi’

BGR - Basalti delle Giare

Ad - Aplite dykes

PG - Perdoseddu granite

MGm - Monte Grighini Granite

ACN - Argilloscisti di Riu Canoni

MGM - Metarcose di Genna Mesa

TZ - Truzzulla Formation

MUZ - Metarenarie di Su Muzzioni

UMz - Ultramylonite zone

MGt - Monte Grighini Tonalite

MGM - Metarcose di Genna Mesa

MSV - Monte Santa Vittoria Formation

MGd - Monte Grighini Diorite

GST - Marne di Gesturi Formation

RML - Marmilla Formation

OMPF - Calc-alkaline volcanics

USS - Ussana Formation

FMC - Monte Cardiga Formation

Heterometric and heterogenic conglomerate with cineritic matrix (U. Aquitaniano - L. Burdigaliano)

Alluvial terraced and in evolution deposit (Holocene - Pleistocene)

Dacitic to basaltic subalkaline and alkaline lavas (Pliocene)

Alternation of arenaceous and clay marl (U. Burdigaliano - M. Langhiano)

Dacitic to ryodacitic pyroclastic flows (Oligo-miocene)

Continental heterometric deposits (U.Oligocene - L. Aquitanian)

Sandstone and quartzite sandstone. Fluvial-deltaic deposits (L. Eocene)

Cataclastic rocks with small bodies of a) shale, b) silicized metalimestone and c) hornfels

Equigranular fine grained muscovite-bearing peraluminous leucogranite

Black shales; a) nodular metalimestones (Silurian - L.Devonian)

Grey-greenish phyllites, a) marble and calcschist (? Silurian - ?L. Carboniferous)

Metarkoses, quartzites and metaconglomerates (U. Ordovician)

a) acidic metavolcanics, b) metarkose and metasandstone (U.Ordovician - 440 Ma)

Garnet-staurolite-andalusite-bearing schist and micaschist (TC)a) white quartzite, b) marble (U. Ordovivcian - Silurian)

Calc-alkaline metapyroclastites with rhyolitic-dacitic composition (?M. - U. Ordovician)

a) intensely fractured medium-grained mylonitic monzogranite (PGm) and b) mylonitic leucogranite (PGl)

Equigranular to disequigranular medium-grained biotite-bearing calc-alkaline monzogranite and granodiorite

Metapelites, a) fossiliferous metasiltites, b) fossiliferous metalimestone (encrinite), (U. Ordovician)

Quartzites, metarsandstone and metaconglomerates (M. - ?U. Ordovician)

Mylonitic and ultramylonitic leucogranites and monzogranites

Equigranular fine-grained calc-alkaline tonalite

Metarkose, quartzites and mtaconglomerates (U.Ordovician)

Intermediate to basic metavolcanites (M.- ?U.Ordovician)

Equigranular fine grained calc-alkaline diorite

POST-PALEOZOIC SEDIMENTARY AND VOLCANIC SUCCESSION

LATE VARISCAN DYKE SYSTEM

LATE VARISCAN SHEAR ZONE

MONTE GRIGHINI INTRUSIVE COMPLEX (305-290 Ma)

GERREI UNIT

CASTELLO MEDUSA UNIT

MONTE GRIGHINI UNIT

VARISCAN BASEMENT

a

b

a

a

b

a

a

b

c

b

STRUCTURALSYMBOLS:

S axial plane foliation2



F fold axis1

F fold axis2

F fold axis 3

stretching/mineral lineation

cataclastic foliation

mylonitic/ultramylonitic foliation

mylonitic stretching lineation

axial plane trace of F antiform 1

and synform


and synform


and synform

main thrust

transtensive fault

normal fault

strike-slip fault

trace of geological sectionA A’

fossiliferous locality

NU

RR

A

I. Asinara

Posada

ARBURESE

Cagliari

Sassari

30 km

ANGLONA

Mt.Grighini

Capo Spartivento

SULCIS

Migmatite complex

Variscan granitoids

Post-Variscan covers

Amphibolite-faciesmetamorphic complex

Internal nappes

External nappes

Sarrabus Unit

Arburese Unit

Mt. Grighini Unit

Gerrei Unit

Meana Sardo Unit

Riu Gruppa-Castello Medusa Units

GERREI

SARCIDANO

Thrusts and foldsexternal zone

Major thrusts

GALLURA

Nuoro

BARBAGIA

SARRABUS

N

IGLESIENTE

Axial zone

Nappe zone

External zone

Tectonic sketch map of Sardinia

Tectonic sketch map

N Allai

M. Fogaies

M. Filighi

M.Grighini

Cuccurue’uas

transtensive fault

shear zone eastern boundary

thrust

Castello Medusa Unit

Monte Grighini Unit

Gerrei Unit

leucogranite

Ms* Ms** 298 ± 5

302 ± 0.24

Ms* Ms** 297 ± 5

300 ±1.2

295 ± 9 Ms**

Bt*** 302 ± 6

299 ± 5 Ms**

Ms** 305 ± 6 Ms* 296 ± 1.5

Bt 304 ± 6 ***

Bt 293 ± 4**

Bt 294 ± 9Bt*** 302 ± 6

**

Ms** 307 ± 5

Radiometric ages (Ma)* Ar/Ar, **Rb/Sr, *** K/Ar 0 1 2km

fault

tonalite-monzogranite

cataclasite

ultramylonite

diorite

Neogene

g

d5000

5

10

15

20

1000 1500 2000

protomylonite zone (0.35 < g <1.15)

st1 mylonite zone (1.15 < g < 5.5)

nd2 mylonite zone (5.5 < g < 11.5)

ultramylonite zone (g > 11.5)

0 1 2km

graph of shear strain (g) vs. width (d) of shear zone

Map distribution of deformation zone based on shear strain (g =2cotan2q’) angle (q’) between shear planes (C-plane) and foliation (S-

plane) in the synkinematic intrusions

variation, calculated on the basis of

Page 19 of 19


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