Geological Map of the Monte Grighini Variscan Complex (Sardinia, Italy)

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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

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1

GEOLOGICAL MAP OF MONTE GRIGHINI VARISCAN BASEMENT

1

(SARDINIA, ITALY)

2

Giovanni Musumeci1, Maria Elena Spano2, Gian Piero Cherchi3, Marcello Franceschelli2, Pier

3

Carlo Pertusati1, Gabriele Cruciani2 4

1

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

2

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

3

ARPAS 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. gm@dst.unipi.it

24 25 26 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59

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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 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58

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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 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59

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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 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58

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

white mica +garnet ± biotite. K-white mica -bearing assemblage dominates in the southern 119 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59

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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).

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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 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59

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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 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58

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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 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59

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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

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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 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58

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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.

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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.

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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.

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

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

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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 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59

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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 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58

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13 278

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. 285 286 287 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59

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288 Figure 1 289 290 291 292 293 294 295 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58

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15 296 Figure 2 297 298 299 300 301 302 303 304 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59

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305 Figure 3 306 307 308 309 310 311 312 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58

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17 313 314 Figure 4 315 316 317 318 319 320 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59

For Peer Review Only

321 322 Figure 5 323 324 325 326 327 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58

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

, P.C.Pertusati

(1)

, G.Cruciani

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

Acn Cz UMz PMg Cza Cza Czb Czc Cz MGm MGm MGm MGt MGl MGl

GERREI UNIT SHEAR ZONE MONTE GRIGHINI UNIT

Toccori Cuccuru Mannu 0 200 -200 400 600 800 SW 0 200 -200 400 600 800 NE

A

A’

MGl PGm PGl MGm MGm MGm MGt MGt Cza Cza Cza Czb Czb Czc Cz UMz Cz 0 200 -200 400 600 0 200 -200 400 600

800 GERREI UNIT SHEAR ZONE MONTE GRIGHINI UNIT 800

Truzzulla

Cuccuru e Uas Ghenniespos

SW NE

B

B’

GERREI UNIT SHEAR ZONE MONTE GRIGHINI UNIT

CASTELLO MEDUSA UNIT Br.cu Fogaies Perda Arrubia Serra Canna Su Cruccuri SW NE Cz _MGl MGm MGd 0 200 400 600 0 200 400 600 800 800 TC

Su Pinnoi

Uss MGL MGL TZb TCa Qd

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.). 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.

A

B

C

C’

C’’

B’

A’

# 0 # 0 # 0 # 0 # 0 # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # 0 # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # 0 # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # 0 # # # 0 # # # 0 # # # # # # # # # # # # # # 0 # 0 # # # # # # # # # # 0 # 0 # # # # # # # # # 0 # # # # # # # # # # # # # # # # # # # # 0 # # # # # # # # # # # # 0 # # # # # # # # # # 0 # # # # # # # # # # # # # # # # 0 # # # # # # # # # # # # # # # # # # # # # # # # # 0 # 0 # # # 0 # 0 # 0 # # # # # 0 # # 0 # 0 # # # # # # # # 0 # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # 0 401.43 393.11 357.85 299.03 344.14 332.80 348.06 283.08 274.95 265.80 264.09 359.21 304.53 307.83 340.76 310.40 328.84 346.30 333.10 334.86 322.59 337.41 354.56 354.41 362.79 383.70 384.62 373.37 377.06 388.97 417.80 425.94 278.16 337.56 334.35 351.51 305.36 314.75 305.42 213.54 234.77 208.25 226.60 234.10 251.83 245.95 286.51 266.90 269.52 283.54 289.78 298.21 289.09 321.17 312.74 281.34 288.08 308.49 338.88 312.84 304.86 312.57 314.44 _321.83 332.69 334.95 344.70 353.13 325.85 343.51 343.00 355.35 350.13 358.56 453.45 440.25 332.19 284.83 276.58 275.23 273.97 197.38 174.32 171.65 213.57 198.78 194.05 177.10 160.20 162.10 154.66 158.22 152.96 166.23 137.65 136.75 126.39 125.73 105.48 84.82 101.29 81.56 167.15 200.72 183.68 194.87 218.69 206.27 265.96 233.05 251.11 284.56 284.98 295.10 356.95 355.51 376.99 259.03 272.88 191.16 167.17 306.00 299.10 294.92 278.00 264.41 208.12 310.27 332.42 409.21 389.68 351.66 356.76 391.47 285.87 283.86 316.59 114.07 112.25 205.61 121.69 310.43 311.69 183.89 184.65 183.77 129.49 107.85 88.39 118.55 103.61 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 84.94 268.51 139.23 129.17 150.69 257.99 173.87 128.81 174.63 170.59 142.87 226.22 176.80 214.12 206.40 216.66 209.14 204.68 273.20 264.94 200.28 180.44 218.38 184.69 211.25 216.59 240.17 235.03 251.17 272.54 270.45 270.99 270.25 288.18 214.69 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 42.77 305.08 202.22 662.72 208.47 235.14 244.95 206.61 296.25 404.93 319.52 275.11 356.15 403.19 401.57 382.54 425.01 280.24 244.59 215.61 274.05 232.41 272.19 270.39 407.14 467.60 460.42 472.89 434.37 307.71 415.89 401.49 148.40 185.21 184.88 266.95 216.94 233.50 227.45 240.81 244.32 253.21 273.32 271.85 280.19 276.59 225.54 238.08 264.32 283.12 270.42 303.12 296.91 297.27 270.90 293.66 281.57 290.27 387.60 376.89 365.73 349.54 386.90 355.79 265.01 302.89 306.91 366.84 370.96 346.75 496.84 492.70 533.18 126.71 344.06 370.99 380.59 382.52 378.26 403.01 385.56 437.07 512.40 617.12 300 250 350 200 400 450 350 300 300 350 300 300 350 350 300 200 250 350 300 300 250 350 300 350 250 350 250 250 300 300 350 400 150 100 200 250 300 250 250 200 150 ₂₀₀ 100 200 200 150 200 300 250 200 250 250 250 150

sa Grutta Saua Madri

Br.cu Fogaies

N.ghe Molas

N.ghe Pra Mesa

CUCCURUE’UAS SARIST ON COST A TRA TZU S'ENA DE SA PIRA N.ghe Griolu PALA SUERGIUS PEDRU MAGGIU SERRA CANNA GENNA PUNTEDDU PERDOSU MANNU SERRA MAIORI M. CRISTU CODINAS DE LAMPU PERDAS ASPAS GRAGALLASA Br.cu Su Saccu

Br.cu Cussorgiu Mannu

FUSTIS ARBUS CONCA BASIGHEDDU TERRA ARGIOLAS PERDA ARRUBIA SANTU PERDU AZZA PULAU CORONAS CUCCURU MANNU SEDDANA CANNUREU PIRESTEDA PERDARBA MATZUZZI LEPORADA PERDA BIANCA SP 39 MASONI ARGHENTU

N.ghe Pra Pinna

N.ghe Minda Iara

COGULA LADOGIAST A ZIODDIA CANNISONE GHENNIESPOS FRISSA M. OLLASTRA Funt.na Liccari N.ghe Liggiu PISEDDU Funt.na Airi Funt.na s'Eremita Funt.na Promonte LACHIXEDDUS TRUZZULLA MURISINU BADUGGIANAS SA PALA MANNA s'Ispelunca Minore Mitza Pabixiabis PICCIORRE MODDIZZI TOCCORI

N.ghe Predi Proccu

N.ghe Bidella SA FUSTINAGA B.cu ENTOSU Bau Accas Nuraxeddu N.ghe MAIORI M. IRONI N.ghe Luas ZIU NARI M. PODDIGAS M. GRIGHINI C. Tatti BENAS M. PAGLIARTANA B.cu SU PINNOI M. FAURRAS M. CORONGIUARBU MINDAPIRA MONTI PALLA C. Sulis C. Marras PRA MAIORI C. Urru C. Pischedda C. Cocco N.ghe Quasigu Cava di Pietra CAMPU TRAIA M.za s' Iscibi SU CRUCCURI C. se Deidda C. Macci PUNTEDDU Nuraxeddu Villaurbana Nuraxeddu Mogorella 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 50 400 250 150 200 450 300 350 500 550 250 300 200 200 100 600 150 150 400 250 350 100 200 100 350 250 200 250 200 100 250 250 450 200 400 300 250 400 350 250 400 350 450 300 350 150 400 150 200 350 250 350 200 150 300 250 200 350 400 350 150 150 81 000 m E 14 82 14 83 14 84 14 85 14 86 14 87 14 ₁₄88 89 14 90 14 25 44 24 44 23 44 22 44 21 44 20 44 19 44 18 44 17 44 16 44 15 44 14 44 13 000 m N 44 25 44 24 44 23 44 22 44 21 44 20 44 19 44 18 44 17 44 16 44 15 44 14 44 13 44 # GIOSTRIS 23

44

22

44

21

44

20

44

19

44

18

44

17

44

16

44

15

44

14

44

13 000mN

44

13

44

24

44

25

44

26

44

23

44

22

44

21

44

20

44

19

44

18

44

17

44

16

44

15

44

14

44

24

44

25

44

26

44

M.FILIGHI 39°51 41’’’ 39°57 00’’’ 39°57 00’’’ 39°54 00’’’ 39°54 00’’’ 39°51 41’’’ 8°46 39°59 ’’’7 39°59 7’’’ 8°54 8°50

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 % S₂ foliation _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 % S₁ foliation n=110 F -F fold axis_{1 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 mineral lineation n=75 ACN RLM RLM RLM RLM GST USS Q Q Q BGR RLM USS RLM RLM RLM RLM RLM OMPF OMPF OMPF OMPF OMPF USS Q RLM RLM RLM RLM RLM RLM RLM RLM RLM RLM OMPF OMPF OMPF OMPF OMPF OMPF _USS USS USS USS USS USS Uss Uss OlMc Q Q Q Q Q OMPF OMPF OMPF OMPF OMPF OMPF OMPF OMPF OMPF OMPF OMPF OMPF OMPF OMPF OMPF OMPF RLM RLM OMPF OMPF OMPF OMPF USS Q Q Q OMPF RLM RLM RLM OMPF OMPF OMPF OMPF OMPF OMPF OMPF OMPF OMPF OMPF OMPF USS Q Q Q Q Q Q Q Q OMPF RLM USS USS Q Q Q BGR BGR RLM RLM USS USS USS USS USS USS USS USS FMC RLM RLM GST USS USS Q Q Q RLM RLM RLM USS Q Q RLM RLM RLM RLM RLM RLM RLM USS BGR BGR Q USS Q USS MRl FMC USS USS MRl USS MRl MRl USS USS USS USS MRl CSA MGM MGM CSA Csa MGM MGM Csa Csa Csa MGM Csaa MGM CSA TC TC TC TCa TC TC TC TC a TZ TZ TZ TZ TC a TCb TC b TC TC TC TC b TC TC TC TC TC TZb TZa TZb TZb TZb TZ TZ TZb TZb TC b b a TC TC TC TC b TCb TCa TC TC TC TC TZa TZb TC TC TC TZb TC TZb TZb TZa TZa TC TC TC TCa TCa TZa TZb TZb TC TC TC TC PRF ACN ACN ACN ACNa ACN SGA ACNa ACNb ACNb ACN MGM ACNa SGA SGAa ACNa MGM ACN PRF ACN PRF PRF ACN ACN PRF ACN ACN MUZ MSV MSV MUZ ACN MSV MUZ PRF MUZ MSV ACN PRF ACN PRF PRF ACN ACN ACN ACN PRF PRF PRF ACN ACN ACN ACN PRF PRF MUZ MSV ACN MSV MUZ MUZ PRF PRF PRF MUZ MSV UMz Cz UMz Cz Czb PGm b Cz UMz Cz Cz PGm Czc Cz PGm CZa PGl PGm SGA UMz Cz Cz UMz UMz Cz Cz Cz MGm MGm MGl MGl MGl MGl MGm MGm Qd MGm MGm _MGm Qd Qd MGd MGd MGt MGt MGd MGm MGd Qd Qd MGd Qd MGd Qd MGl Qd MGm MGm Qd Qd MGl MGl MGt MGm MGm MGd Ad Qd Qd MGl MGm MGl MGt MGm MGm MGl MGd Qd MGl MGm Qd Qd MGl Qd Qd MGm MGd MGl MGl Ad Qd MGl MGd Ad Ad Ad Qd MGl MGm MGl Ad MGm 30 40 45 20 20 65 57 55 60 40 45 40 15 70 45 60 55 50 50 25 50 60 70 80 80 80 ₇₅ 70 80 80 75 65 80 25 75 85 80 20 ₇₀ 15 80 60 80 80 25 85 70 70 75 25 70 65 80 75 20 70 80 70 15 80 75 85 50 60 80 10 70 80 85 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 65 40 35 40 45 40 30 45 60 80 80 75 80 10 27 80 70 75 75 25 45 45 50 60 45 40 45 40 25 15 30 25 15 40 30 25 50 25 50 25 10 25 30 45 35 50 25 15 30 10 45 60 75 40 10 45 25 40 20 55 50 60 35 25 50 40 40 45 50 40 30 20 10 30 35 20 35 40 60 40 35 60 45 25 10 15 30 35 25 30 35 35 35 25 20 20 30 10 55 45 30 75 80 70 40 25 35 10 50 50 65 15 20 55 12 10 45 30 30 50 45 40 55 10 15 50 65 65 65 70 65 80 20 45 80 70 75 15 50 12 70 75 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 1Km 1250 1500 1750 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

STRUCTURAL

SYMBOLS:

S axial plane foliation2

S axial plane foliation1

S axial plane foliation3

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

axial plane trace of F antiform 2

and synform

axial plane trace of F antiform 3

and synform main thrust

transtensive fault normal fault

strike-slip fault

trace of geological section

A A’ fossiliferous locality NURRA I. Asinara Posada ARBURESE Cagliari Sassari 30 km ANGLONA Mt.Grighini Capo Spartivento SULCIS Migmatite complex Variscan granitoids Post-Variscan covers Amphibolite-facies metamorphic 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 folds external 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 ± 9 Bt*** 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 d 500 0 5 10 15 20 1000 1500 2000 protomylonite zone (0.35 < g <1.15) st 1 mylonite zone (1.15 < g < 5.5) nd 2 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

2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60