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ÑÏÈÑÀÍÈÅ ÍÀ ÁÚËÃÀÐÑÊÎÒÎ ÃÅÎËÎÃÈ×ÅÑÊÎ ÄÐÓÆÅÑÒÂÎ, ãîä. 68, êí. 1—3, 2007, ñ. 46—65

REVIEW OF THE BULGARIAN GEOLOGICAL SOCIETY, vol. 68, part 1—3, 2007, p. 46—65

Magmatic rocks and evolution of the Late Cretaceousmagmatism in the region of the Asarel porphyry copper deposit,Central Srednogorie, Bulgaria

Rossen Nedialkov1, Aneta Zartova1, Robert Moritz2

1 Sofia University “St. Kliment Ohridski”, FGG; E-mail: rned@gea.uni-sofia.bg2 University of Geneva; E-mail: Robert.Moritz@terre.unige.ch

Ð. Íåäÿëêîâ, À. Çàðòîâà, Ð. Ìîðèö. 2007. Ìàãìåíè ñêàëè è åâîëþöèÿ íà êúñíîêðåäíèÿ ìàãìàòèçúìïðè ìåäíî-ïîðôèðíî íàõîäèùå Àñàðåë, Öåíòðàëíî Ñðåäíîãîðèå, Áúëãàðèÿ. – Ñï. Áúëã. ãåîë. ä-âî,68, 1—3, 46—65.

Ðåçþìå. Ìàãìàòèçìüò íà ìåäíî-ïîðôèðíîòî íàõîäèùå Àñàðåë äîñåãà íå å áèë èçñëåäâàí öåëåíàñî÷åíî.Ìàãìàòè÷íèÿò öåíòüð å èçãðàäåí îò âóëêàíèòè (àìôèáîëîâè àíäåçèòè äî ëàòèòè, ïèðîêñåí-àìôèáîëîâè àíäå-çèòîáàçàëòè äî øîøîíèòè è áèîòèò-àìôèáîëîâè äî àìôèáîë-áèîòèòîâè àíäåçèòè), êîèòî çàëÿãàò âúðõó ñêàëè-òå íà öîêúëà (ìåòàìîðôèòè è ïàëåîçîéñêè ãðàíèòîèäè íà Ñìèëoâåíñêèÿ ïëóòîí). Ñðåä àíäåçèòîáàçàëòèòå ñåóñòàíîâÿâàò ìàëêè òúìíè çàîáëåíè ìàãìàòè÷íè âêëþ÷åíèÿ ñ áëèçúê äî áàçàëòîâ è ïèðîêñåíèòîâ ñúñòàâ. Ñðåäñêàëèòå íà öîêúëà è âóëêàíèòèòå å âíåäðåía Àñàðåëñêàòà ìàëêà ïîðôèðèòîâà èíòðóçèÿ èçãðàäåíà îò òðè ôàçè:1) Q-äèîðèòîâ äî Q-ìîíöîíèòîâ ïîðôèðèò; 2) Q-ìîíöîíèò äî ãðàíîäèîðèò ïîðôèðè; 3) ãðàíèò-ïîðôèð. Ìàã-ìàòè÷íèòå ïðîöåñè îïðåäåëèëè ìàãìàòè÷íîòî ðàçíîîáðàçèå ñà êðèñòàëèçàöèîííàòà äèôåðåíöèàöèÿ è ñìåñ-âàíåòî íà ìàãìè. Êðèñòàëèçàöèîííàòà äèôåðåíöèàöèÿ å ñâúðçàíà ñ ôðàêöèîíèðàíå íà ïèðîêñåí, àìôèáîë,ìàãíåòèò è àïàòèò. Ìàãìàòèçìúò ïðîòè÷à â îáñòàíîâêà ñâúðçàíà ñ ïðîöåñ íà ñóáäóêöèÿ è ñ îòíîñèòåëíî âè-ñîêî âîäíî ñúäúðæàíèå â ìàãìàòà. Òåìïåðàòóðàòà íà êðèñòàëèçàöèÿ íà àìôèáîë-ïëàãèîêëàçîâîòî ðàâíîâå-ñèå ïðè âóëêàíèòèòå å â èíòåðâàëà îò 730 äî 910° Ñ ïðè íàëÿãàíèÿ îò 4 äî 9 kb, à çà ïàëåîçîéñêèòå ãðàíîäèîðè-òè íà Ñìèëîâåíñêèÿ ïëóòîí – òåìïåðàòóðà íà êðèñòàëèçàöèÿ îêîëî 760° Ñ è íàëÿãàíå îêîëî 4,5—5,5 kb.

Êëþ÷îâè äóìè: ïåòðîëîãèÿ, Àñàðåëñêî ìåäíî-ïîðôèðíî íàõîäèùå, òåðìî-áàðè÷íè óñëîâèÿ, òåêòîíñêàîáñòàíîâêà.

Abstract. The magmatic evolution of the Asarel porphyry copper deposit has not been studied until now. The mag-matic center includes volcanites (amphibole andesites to latites, pyroxene-amphibole basaltic andesites to shoshonitesand biotite-amphibole to amphibole-biotite andesites), disposed over the rocks of the basement (metamorphic rocks andthe Paleozoic granitoides of the Smilovene pluton). Among the basaltic andesites, small rounded mafic enclaves withbasaltic to pyroxenitic composition were established. The volcanites and the basement rocks were intruded by the smallporphyritic pluton of Asarel composed of three phases: 1) Q-diorite to Q-monzonite porphyrites; 2) Q-monzonite togranodiorite porphyries; 3) granite porphyries. The magmatic diversity is defined by the processes of magma mixing andcrystallization differentiation, the later being related to the fractionation of pyroxene, amphibole, magnetite and apatite.The magmatism evolved in subduction related tectonic setting in high water content conditions. The estimation of thecrystallization parameters for the volcanic rocks are based on the Al content in amphibole (P = 4—9 kb) and the amphib-ole-plagioclase equilibrium (T = 730—910° Ñ). The pressure estimated for the Paleozoic granitoides, is 4.5—5.5 kb and thetemperature of crystallization – 760° Ñ.

Key words: petrology, Asarel porphyry copper deposit, thermobarometry, tectonic setting.

Introduction

The region of the Asarel porphyry copper deposit issituated in the central part of the Srednogorie zonenear the town of Panagyurishte. The Srednogorie zoneis a part of the Apuseni—Banat—Timok—SrednogorieBelt (Popov et al., 2000), characterized by upper cre-taceous magmatism and the disposition of numer-ous copper, gold-copper, copper-molybdenum andcopper-base metal deposits and occurrences. Main

factors controlling the ore generation and ore em-placement are magmatism and tectonics.

The petrology of the Paleozoic granitoides andCretaceous magmatites was studied essentially outof the areas of the ore deposits, where rocks are oftenaffected by hydrothermal alteration (Dabovski et al.,1965; Boyadjiev, 1979, 1993; Arnaudov et al., 1989;Peytcheva et al., 2001; Ivanov et al., 2001). The Up-per Cretaceous volcanism and coeval plutonic mag-matism were studied by Ushev (1962), Chipchakova

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(1970), Dimitrov (1983), Stanisheva-Vassileva, (1980),Bogdanov (1987), Popov (1981), Ignatovski and Bairak-tarov (1996), Lilov and Chipchakova (1999), Kame-nov et al. (2003, 2004), Von Quadt and Peytcheva(2004). The metallogenic importance of the magmaticcenters renewed the interest on the magmatism ofthe Central Srednogorie. The Asarel magmatic cen-ter is related to one of the biggest porphyry copperdeposits in Europe and its study as a fertile magmat-ic system is very interesting.

In the present paper, we aim to give details aboutthe magmatic rocks in the area of the Asarel por-phyry copper deposit and also the magmatic evolu-tion of the Upper Cretaceous magmatic center, sincebeing of key importance for the formation of theporphyry copper ore system.

Geology

The geological structure of the Central SrednogorieZone (CSZ) is defined by two main units: a Palaeo-zoic basement and a Mesozoic—Tertiary cover.

The basement rocks of CSZ are product of high-grade metamorphism with Paleozoic age (408 ± 40Ma; 480 ± 30 Ma; 485 ± 50 Ma – U-Pb method onzircons – Arnaudov et al., 1989 and 316—317 Ma –Velichkova et al., 2001). They were intruded by Up-per Carboniferous granitoids as well as gabbroic andultrabasic plutonic bodies.

The Mesozoic cover of CSZ consists of Triassicand Cretaceous sediments and volcanites (Karagju-leva et al., 1974). The Triassic sediments (sandstones,limestones and conglomerates) outcrop essentially in

Fig. 1. Geologic sketch map of the region of the Panagyurishte ore region with indication of the Asarel and Medet porphyrycopper deposits (after Ignatovski, Bayraktarov, 1996, with changes)

Ôèã. 1. Îïðîñòåíà ãåîëîæêà êàðòà íà Ïàíàãþðñêèÿ ðóäåí ðàéîí ñ ðàçïîëîæåíèå íà ìåäíî-ïîðôèðíèòå íàõîäèùàÀñàðåë è Ìåäåò (ïî Ignatovski, Bayraktarov, 1996, ñ èçìåíåíèÿ)1 – òåðöèåðíè è êâàòåðíåðíè ñåäèìåíòè; 2 – Ê2 ïîñòâóëêàíñêè ñåäèìåíòè; 3 – Ê2 ïîðôèðèòîâè ïëóòîíè÷íè ñêàëè;4 – âóëêàíñêè ñêàëè îò Ðàäêèíñêàòà âóëêàíñêà èâèöà; 5 – âóëêàíñêè ñêàëè îò Ïåñîâåöñêàòà âóëêàíñêà èâèöà; 6 –âóëêàíñêè ñêàëè îò Êðàñåí–Ïåòåëîâñêàòà âóëêàíñêà èâèöà; 7 – âóëêàíñêè ñêàëè îò Àñàðåëñêàòà âóëêàíñêà èâèöà;8 – Ê2 äîâóëêàíñêè ñåäèìåíòè; 9 – òðèàñêè ñåäèìåíòè; 10 – Pz ãðàíèòîèäíè èíòðóçèè; 11 – Pz ãàáðîèäíè èíòðóçèè;12 – Pz ìåòàìîðôíè ñêàëè îò ôóíäàìåíòà; 13 – ðàçëîìè; 14 – âúçñåäíè çîíè

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the western part of the Panagyurishte region. UpperCretaceous volcanites and sediments are disposed inbasins with WNW direction. À volcano-sedimentarytephroidal flysch was formed mutually with the vol-canism in the western part of the Panagyurishte re-gion (Dimitrova et al., 1984). The terrigenous flysch(conglomerates, sandstones, siltstones and marls witha specific red colored marl layer at the top) wasformed after the volcanic activity. In the followedcompression that folded CSZ, volcanites formed an-ticlinal stripes with the same WNW direction (Dimi-trov, 1983). Toward the end of the Senonian mag-matic activity, small subvolcanic to hypabyssal in-trusives and dykes crosscut the volcanites and therocks of the basement. The rocks in the magmaticcenter are affected by synchronous to magmatism orpostmagmatic hydrothermal alteration that preced-ed or was synchronous to the ore formation.

The Asarel copper porphyry deposit is disposed7 km northwest of the town of Panagyurishte in CSZ.It is controlled by the intersection of the Asarel vol-

canic stripe (emplaced in strike-slip basins formedby faults with ESE-WNW direction (100—130°) –Ivanov et al., 2001) with the deep faults of the Pa-nagyurishte corridor with NNW direction (Tzvetkovet al., 1978). The Asarel deposit is situated in themost eastern part of the Asarel volcanic stripe (Fig. 1).The deposit basement is presented by biotite or twomica gneisses and the rocks of the Variscan Smilovenepluton (330—320 Ma – Arnaudov et al., 1989; 307.7± 4.5 Ma – Von Quadt, Peytcheva, 2004; 305.3 ±1.3 Ma – Peytcheva et al., 2004; 304.1±5.5 Ma –Carrigan et al., 2005). The pluton was formed in threemagmatic phases. The first one, which dominates,produced equigranular coarse-grained granodiorites.The rocks of the second phase are equigranular fine-grained granites, showing sharp intrusive contactswith the granodiorites. The third phase is presentedby pegmatites and aplites.

The volcanic structures are weekly preserved andepiclastic rocks predominate in the Asarel volcanicstripe. Pyroclastic rocks and lava flows in their initial

Fig. 2. Geologic map of the open pit mine of the Asarel porphyry copper deposit (horizon 885) (after the investigations of thegeologic survey of the Asarel mine, with changes)

Ôèã. 2. Ãåîëîæêà êàðòà íà õ-ò 885 îò îòêðèòèÿ ðóäíèê íà ìåäíî ïîðôèðíî íàõîäèùå Àñàðåë (ïî ìàòåðèàëè íàãåîëîæêàòà ñëóæáà íà ðóäíèêà ñ ìàëêè èçìeíåíèÿ)1 – âóëêàíñêè ñêàëè; 2 – ïîðôèðèòîâè èíòðóçèâíè ñêàëè: à) êâàðöìîíöîíèòîâ ïîðôèðèò; b) ãðàíîäèîðèò ïîðôèð(II ôàçà); ñ) ãðàíèò ïîðôèð; 3 – ïàëåîçîéñêè ãðàíèòîèäè; 4 – ðàçëîìè; 5 – ãåîëîæêè ãðàíèöè

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position are rare. Subvolcanic bodies, dykes and necksare relatively well preserved and their concentrationin some places gave us the possibility to suppose thepresence of the volcanic centers and to follow themagmatic evolution. First were formed Hb andesitesto latites, presented by epiclastic rocks and occasion-ally lava flows, and pyroclastic rocks. They composethe major part of the Asarel volcanic stripe. The sec-ond phase is related to the formation of several neckswith isometric or oval in cross section colon-like bod-ies of clinopyroxene-amphibole to amphibole twopyroxene basaltic andesites incorporating smallrounded mafic magmatic enclaves. Occasional ba-saltic andesite pyroclastic rocks (psammitic tuffs),dykes and epiclastic rocks also occur. The third vol-canic event is related to the formation of subvolcanicbodies (isometric or elongated in WNW direction) ofbiotite-amphibole to amphibole-biotite andesites,quartz-andesites to dacites, crosscutting all of thepreviously formed effusive and volcaniclastic rocks.

The porphyritic intrusive rocks are disposed essen-tially in the Asarel magmatic center and northern ofit. They were intruded in both of the volcanites andthe basement rocks (metamorphics and the Paleozoicgranitoides of the Smilovene pluton). In the centralpart of the Asarel deposit, all the rocks of the base-ment, the volcanites and the subvolcanic porphyriticrocks are strongly hydrothermally altered (K-silicate,argillitic, advanced argillitic, quartz-sericitic and pro-pylitic alterations – Arnaudova et al., 1991; Kanazir-ski et al., 1995, 2000). Nevertheless, in the northernpart of the deposit, less affected by the alteration apo-physes of the pluton gave us the possibility to distin-guish three successive impulses. Chilled zones betweenthe different magmatic phases observed in polyphaseformed dyke bodies (Fig. 2) determine the intrusivemagmatic evolution: 1) fine to medium porphyriticQ-diorite to Q-monzonites; 2) Q-monzonite porphy-ries to granodiorites porphyries; 3) granite porphyry.

Petrography of the magmatic rocks

Paleozoic granitoides

The Paleozoic granitoides of the Smilovene plutonare studied as they were host rocks for the late Creta-ceous plutonics and the porphyry copper deposit,and they can give us new information about the Pa-leozoic geology.

Granodiorites are massive, leuco- to mesocratic withgranitic texture and local elements of monzonitic. Theyare composed of plagioclase (oligoclase – andesineAn28—35 (Table 1), potassic feldspar (perthitic – Or90—93Ab8—5 Cn1—2), quartz, amphibole (magnesiohornblende,sometimes modified in actinolite – Table 2) and bi-otite (Table 3). The mafic minerals are often slightlyaltered. The accessory minerals are presented by apa-tite, zircon, titanite and rare magnetite and alanite.Few dark xenoliths and enclaves were established inthe granodiorites. A xenoblock (with dimensions2—3 m) of Paleozoic gabbro was found in the later,

Table 1Chemical composition (in wt. %) and mineral formulae ofplagioclases and K-feldspars (calculated at 8 – oxygens)from the intrusive rocks of the Smilovene pluton (selectedanalyses)

Òàáëèöà 1Õèìè÷åí ñúñòàâ (â òåãë. %) è êðèñòàëîõèìè÷íè ôîð-ìóëè íà ïëàãèîêëàçè è êàëèåâè ôåëäøïàòè (ïðåèç÷èñëåíèêúì 8 êèñëîðîäà) îò èíòðóçèâíèòå ñêàëè íà Ñìèëî-âåíñêèÿ ïëóòîí (èçáðàíè àíàëèçè)

Gd, granodiorites; Gr, granites; Pl, plagioclase; KFs, potassicfeldspar

Gd – ãðàíîäèîðèòè; Gr – ãðàíèòè; Pl – ïëàãèîêëàç; KFs –êàëèåâ ôåëäøïàò

which let us presume that the Paleozoic gabbros wereformed before the granitoid magmatism.

Granites are fine-grained and equigranular. Theywere established in the northern part of the open pitmine of Asarel. Their texture is granitic with elementsof monzonitic. The granite is composed of plagio-clase (slightly zoned – oligoclase to andesine An28—38– Table 1), potassic feldspar (twinned microcline),quartz and biotite. The accessory minerals are apa-tite and zircon.

Pegmatites and aplites occur essentially as veins.The aplites are up to 35 cm thick and the pegmatiteveins – up to 2—3 m. Some of them are with curvedshape and thickened sectors. Aplites are fine grained,white to pale pink in color, with small occasionaleuhedral plagioclases and rare biotite. Pegmatites arecomposed of plagioclase, perthitic K-feldspar ormicrocline, quartz, muscovite and rare biotite.

Sample 17a 15 40 40 17a 17a Rock Gd Gd Gr Gr Gd Gd mineral Pl Pl Pl Pl KFs KFs SiO2 59.26 66.25 59.15 60.04 64.03 64.31 TiO2 0.00 0.00 0.00 0.00 0.00 0.00 Al2O3 25.89 21.85 25.98 25.25 18.50 18.26 FeO 0.00 0.00 0.00 0.00 0.12 0.19 MnO 0.00 0.07 0.00 0.00 0.00 0.00 MgO 0.00 0.67 1.36 0.52 0.00 0.00 CaO 6.87 5.33 5.3 7.46 0.16 0.00 Na2O 7.31 5.29 7.58 6.81 0.58 0.93 K2O 0.24 0.21 0.21 0.00 15.68 15.79 BaO 0.00 0.00 0.00 0.00 0.26 0.35 Total 99.57 99.67 99.58 100.08 99.33 99.83 Si 2.65 2.89 2.64 2.67 2.98 2.99 Ti 0.00 0.00 0.00 0.00 0.00 0.00 IVAl 1.36 1.24 1.36 1.32 1.02 1.00 Fe 0.00 0.00 0.00 0.00 0.00 0.01 Mn 0.00 0.00 0.00 0.00 0.00 0.00 Mg 0.00 0.04 0.09 0.03 0.00 0.00 Ca 0.33 0.25 0.25 0.36 0.01 0.00 Na 0.63 0.45 0.66 0.59 0.05 0.08 K 0.01 0.01 0.01 0.00 0.93 0.94 Ba 0.00 0.00 0.00 0.00 0.01 0.02 An 33 35.1 27.5 37.7 1.00 0.0 Ab 63 63.2 71.2 62.3 5.00 7.69 Or 1.0 1.7 1.3 0.0 93.00 90.38 Cn 0.0 0.0 0.0 0.0 1.00 1.92

7 Ñïèñàíèå íà Áúëãàðñêîòî ãåîëîãè÷åñêî äðóæåñòâî, êí. 1—3, 2007

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Sample 15 17a 17a 17a SiO2 53.880 48.020 48.790 54.130 TiO2 0.000 0.570 0.530 0.000 Al2O3 5.020 9.380 7.680 5.860 FeO 11.830 15.560 15.920 12.760 MnO 0.270 0.330 0.490 0.510 MgO 14.160 10.790 10.950 11.640 CaO 12.930 12.160 12.940 12.600 Na2O 0.290 0.000 0.000 0.000 K2O 0.000 0.790 0.690 0.080 Total 98.380 97.600 97.990 97.580 Si 7.695 7.024 7.184 7.864 IVAl 0.305 0.976 0.816 0.136 T 8.000 8.000 8.000 8.000 VIAl 0.540 0.640 0.516 0.866 Fe3+ 0.000 0.251 0.000 0.000 Ti 0.000 0.063 0.059 0.000 Mg 3.015 2.353 2.404 2.521 Fe2+ 1.413 1.652 1.960 1.550 Mn 0.033 0.041 0.061 0.063 C 5.000 5.000 5.000 5.000 Ca 1.979 1.906 2.000 1.961 Na 0.021 0.000 0.000 0.000 B 2.000 1.906 2.000 1.961 Ca 0.000 0.000 0.041 0.000 Na 0.059 0.000 0.000 0.000 K 0.000 0.147 0.130 0.015 A 0.059 0.147 0.171 0.015 Mg# 0.680 0.590 0.550 0.620

Table 2Chemical composition (in wt. %) and mineral formulae of amphi-boles (calculated on 23 oxygens – 13eCNK) of selected analysesfor amphiboles from the granodiorites of the Smilovene pluton

Òàáëèöà 2Õèìè÷åí ñúñòàâ (â òåãë. %) è êðèñòàëîõèìè÷íè ôîðìóëèçà àìôèáîëè (ïðåèç÷èñëåíè íà áàçàòà íà 23 êèñëîðîäà –13eCNK) îò ãðàíîäèîðèòèòå íà Ñìèëîâåíñêèÿ ïëóòîí

Table 3Chemical composition (in wt. %) and mineral formulae(calculated on 24 oxygens) of biotites from the intrusive rocksof the Smilovene pluton

Òàáëèöà 3Õèìè÷åí ñúñòàâ (â òåãë. %) è êðèñòàëîõèìè÷íè ôîðìóëè(ïðåèç÷èñëåíè íà áàçàòà íà 24 êèñëîðîäà) çà áèîòèòèîò èíòðóçèâíèòå ñêàëè íà Ñìèëîâåíñêèÿ ïëóòîí

Gd, granodiorites;

Gd – ãðàíîäèîðèòè;

Upper Cretaceous magmatic rocks

Near the Asarel magmatic center the volcanites areintensively altered (hydrothermally), that is why theyare studied and described in the Asarel VolcanicStripe (AVS) western of the open pit mine.

Amphibole andesites and latites form the mainpart of the AVS. They could not be clearly distin-guished macro- and microscopically, so they aredescribed together and we will refer to both of therock types as latites from now on, since the later pre-dominate. The rocks are mainly epiclastic and lesspyroclastic (agglomerate and psammitic tuffs). Mas-sive amphibole latites from lava flows and occasion-al dikes are also present. The latites are porphyriticwith hyalopilitic to recrystallized groundmass andphenocrysts presented by zoned plagioclase (two gen-erations, considering their morphology and relations)and amphibole (tschermakite, after the amphiboleclassification of Leake et al., 1997 – Table 4). Theaccessory minerals are titanomagnetite, apatite andpirrhotite as inclusions in amphibole.

The plagioclases from the first generation is round-ed or irregularly shaped and are often enclosed inthe plagioclase of the second generation, presentedby euhedral zoned crystals (andesine An45 – Table 5).

The amphiboles are occasionally zoned and the vol-canic glass of the groundmass in all of the studiedsamples is recrystallized.

The cementing groundmass of the epiclastic rockswas formed by the supergene destruction of the sameamphibole latites.

Pyroxene-amphibole and amphibole-pyroxene ba-saltic andesites to shoshonites. Pyroxene-amphibolebasaltic andesites prevail over the other varieties fromthis group. They are massive with porphyritic textureand hyalopilitic, pilotaxitic or completely recrystal-lized groundmass. Plagioclase, amphibole and cli-nopyroxene phenocrysts are present. The accessoryminerals are titanomagnetite and apatite, as well aspyrrhotite and chalcopyrite as inclusions in the am-phiboles and clinopyroxenes.

There are three generations of plagioclase. Thefirst one is observed as magmatically corroded crys-tals with irregular contours and often sieved texture(Fig. 3A), while the second generation is presentedby euhedral zoned bytownite to oligoclase – An79—15(Table 5).. Plagioclase microlites form the third gen-eration. The amphibole is brown, euhedral and some-times opacitized. Melt inclusions with gas bubblesand ore minerals were trapped in it (Fig. 3B). Theamphiboles are presented by phenocrysts with mag-

Sample 15 17a 17a Rock Gd Gd Gd SiO2 37.19 38.04 37.72 TiO2 1.90 2.24 1.99 Al2O3 19.09 15.6 16.00 FeO 18.56 18.75 19.63 MnO 0.25 0.39 0.00 MgO 11.24 11.05 10.59 CaO 0.00 0.00 0.06 Na2O 0.00 0.00 0.00 K2O 9.40 10.16 9.88 Total 97.63 96.23 95.87 Si 5.97 6.25 6.23 IVAl 2.03 1.75 1.77 VIAl 1.58 1.27 1.34 Ti 0.23 0.28 0.25 Fe 2.49 2.58 2.71 Mn 0.03 0.05 0.00 Mg 2.69 2.71 2.61 Ca 0.00 0.00 0.01 Na 0.00 0.00 0.00 K 1.93 2.13 2.08 Mg# 0.52 0.51 0.49

Fig. 3. Microphotographs showing peculiarities of the late cretaceous magmatic rocks form the Asarel AreaA, big phenocryst of plagioclase I generation with sieve texture, corroded during the magmatic stage. Plagioclase II is presentedby small euhedral phenocrysts. Crossed Nicols, scale bar – 1 mm; B, melt inclusion with bubble and sulfide inclusion with fishtail morphology in amphibole phenocryst from basaltic andesites. Parallel Nicols, scale bare – 100 µm; C, rounded sulfide inclusions(pyrrhotite – arrows) in amphibole from the basaltic andesites. Reflected light, Scale bar – 100 µm; D, small mafic enclave inbasaltic andesites built up essentially by clinopyroxenes and small amounts of plagioclase (2—5%). The arrow is showing asmall euhedral flake of biotite. Parallel Nicols, scale bare – 1 mm; Å, elongated enclave built up by clinopyroxene, plagioclase,amphibole and opaque mineral in basaltic andesites. The periphery of the enclave consists essentially of fine grained clinopyroxene.Parallel Nicols, scale bare – 1 mm; F, miarolitic cavity in the groundmass of a granodiorite porphyry of the Asarel intrusionbordered with potassic feldspar, fulfilled by secondary hydrothermal quartz. Crossed Nicols, scale bar – 1 mm

Ôèã. 3. Ìèêðîñêîïñêè ôîòîãðàôèè ïîêàçâàùè ïåòðîãðàôñêè îñîáåíîñòè íà ãîðíîêðåäíèòå ñêàëè îò ðàéîíà íàÀñàðåëÀ – ãîëÿì ôåíîêðèñòàë îò ïëàãèîêëàç I ãåíåðàöèÿ ñ „ðåøåòåñòà“ ñòðóêòóðà, êîðîäèðàí ïî âðåìå íà ìàãìàòè÷íèÿñòàäèé. Ïëàãèîêëàç II å ïðåäñòàâåí îò ìàëêè èäèîìîðôíè ïîðôèðè. Êðúñòîñàíè íèêîëè, ìàùàáíàòà ëèíèéêà îòãî-âàðÿ íà 1 mm;  – ñòúêëîâàòî âêëþ÷åíèå ñ ãàâîâ ìåõóð è ñóëôèäíî âêëþ÷åíèå ñúñ ñëîæíà ìîðôîëîãèÿ íàïîäîáÿâà-ùà ðèáåíà îïàøêà âúâ ôåíîêðèñòàë îò àìôèáîë ïðè àíäåçèòîáàçàëòè. Ïðîõîäÿùà ñâåòëèíà, ïàðàëåëíè íèêîëè,ìàùàáíàòà ëèíèéêà îòãîâàðÿ íà 100 µm; C – ñóëôèäíî âêëþ÷åíèå (ïèðîòèí óêàçàí îò ñòðåëêèòå) â àìôèáîë îòàíäåçèòîáàçàëòèòå. Îòðàçåíà ñâåòëèíà, ìàùàáíàòà ëèíèéêà îòãîâàðÿ íà 100 µm; D – ìàëêî ìàôè÷íî âêëþ÷åíèåèçãðàäåíî ïðåäèìíî îò êëèíîïèðîêñåí è ìàëêî ïëàãèîêëàç (2—5%) ðàçïîëîæåíî â îñíîâíàòà ìàñà íà àíîäåçèòîáà-çàëò. Ñòðåëêàòà ïîêàçâà åäèíè÷åí êðèñòàë îò èäèîìîðôåí áèîòèò. Ïàðàëåëíè íèêîëè, ìàùàáíàòà ëèíèéêà îòãîâàðÿíà 1 mm; Å – èçäúëæåíî ìàãìàòè÷íî âêëþ÷åíèå èçãðàäåíî îò êëèíîïèðîêñåí, ïëàãèîêëàç, àìôèáîë è ðóäåí ìèíåðàë.Äðåáíîçúðíåñòèÿò âåíåö ïî ïåðèôåðèÿòà íà âêëþ÷åíèåòî å èçãðàäåí ïðåäèìíî îò êëèíîïèðîêñåí. Ïàðàëåëíè íèêî-ëè, ìàùàáíàòà ëèíèéêà îòãîâàðÿ íà 1 mm; F – ìàëêà ìèàðîëà ñ ïåãìàòîèäíà ïåðèôåðèÿ îò êàëèåâ ôåëäøïàò,ðàçïîëîæåíà â îñíîâíàòà ìàñà íà ãðàíîäèîðèò-ïîðôèðèò îò Àñàðåëñêàòà èíòðóçèÿ, êàòî öåíòðàëíàòà ÷àñò å çàïúë-íåíà ñ õèäðîòåðìàëåí êâàðö. Êðúñòîñàíè íèêîëè, ìàùàáíàòà ëèíèéêà îòãîâàðÿ íà 1 mm

Tab

le 4

Che

mic

al c

ompo

sitio

n (in

wt.

%)

and

min

eral

for

mul

ae o

f am

phib

oles

(ca

lcul

ated

at 23

oxy

gens

– 1

3eCN

K)

from

vol

cani

c ro

cks

of the

Asa

rel vo

lcan

ic s

trip

e (s

elec

ted

anal

yses

)

Òàáë

èöà

4Õèì

è÷åí

ñúñ

òàâ

(â

òåã

ë. %

) è

êðèñ

òàë

îõèì

è÷íè

ôîð

ìóë

è (ï

ðåèç

÷èñë

åíè

êúì

23

êèñë

îðîä

à – 1

3eCN

K)

íà à

ìô

èáîë

è îò

âóë

êàíñ

êè ñ

êàëè

îò

Àñà

ðåëñ

êàò

àâó

ëêàí

ñêà

èâèö

à (è

çáðà

íè à

íàëè

çè)

An,

am

phib

ole

ande

site

s to

lat

ites

; BÀ

n, b

asal

tic

ande

site

s; B

i-An,

bio

tite

-am

phib

ole

ande

site

s

An –

àì

ôèá

îëîâ

è àí

äåçè

òè ä

î ëà

òèòè

; BÀn –

àíä

åçèò

îáàç

àëòè

; Bi-An –

áèî

òèò-

àìô

èáîë

îâè

àíäå

çèòè

Sam

ple

30

30

28

28

28

bkx1

bk

x1

bkx1

bk

x1

bkx3

bk

x3

51

51'

51'

51'

Roc

k A

n A

n B

An

BA

n B

An

BA

n B

An

BА

n BА

n

BА

n BА

n B

i-An

Bi-A

n B

i-An

Bi-A

n Si

O2

43.0

5 42

.91

43.5

2 41

.18

41.9

2 46

.92

39.2

5 45

.12

45.4

6 42

.45

40.9

2 44

.99

44.6

1 43

.94

46.5

4 Ti

O2

1.25

1.

55

1.28

1.

79

1.90

1.

58

1.40

1.

64

1.41

1.

51

1.52

1.

09

1.26

1.

29

1.06

A

l 2O3

14.6

5 15

.36

10.9

0 13

.26

11.4

5 17

.11

15.9

8 14

.01

13.1

3 13

.40

14.7

1 10

.94

10.6

3 10

.73

9.92

Fe

O

12.8

1 12

.90

15.5

8 14

.47

16.7

6 8.

03

14.1

9 10

.49

11.3

7 10

.55

11.8

3 12

.76

13.2

9 14

.95

12.8

8 M

nO

0.36

0.

00

0.41

0.

00

0.35

0.

00

0.20

0.

00

0.23

0.

00

0.00

0.

60

0.59

0.

53

0.35

M

gO

12.1

7 11

.83

11.7

2 12

.08

11.2

7 12

.89

12.1

5 14

.59

13.7

3 15

.21

14.1

7 14

.45

14.3

4 13

.19

14.7

8 C

aO

11.8

7 11

.61

11.6

1 12

.40

12.7

7 8.

43

12.7

6 9.

80

10.0

0 12

.72

12.4

9 10

.51

11.0

5 11

.29

10.9

7 N

a 2O

1.

42

1.42

2.

18

2.32

1.

21

2.82

1.

68

2.50

2.

27

0.61

1.

14

2.11

1.

60

1.55

1.

17

K2O

0.

66

0.77

0.

51

0.97

0.

80

0.53

0.

70

0.00

0.

00

1.08

0.

72

0.61

0.

81

0.72

0.

75

Tota

l 98

.27

98.3

5 97

.71

98.4

7 98

.40

98.3

1 98

.31

98.1

5 97

.60

97.5

3 97

.58

98.0

6 98

.18

98.1

9 98

.42

Si

6.18

8 6.

158

6.41

7 6.

066

6.19

8 6.

476

5.71

6 6.

282

6.41

3 6.

073

5.88

4 6.

398

6.36

8 6.

336

6.56

8 IV

Al

1.81

2 1.

842

1.58

3 1.

934

1.80

2 1.

524

2.28

4 1.

718

1.58

6 1.

927

2.11

6 1.

602

1.63

2 1.

664

1.43

2 T

8.

000

8.00

0 8.

000

8.00

0 8.

000

8.00

0 8.

000

8.00

0 8.

000

8.00

0 8.

000

8.00

0 8.

000

8.00

0 8.

000

VI A

l 0.

668

0.75

4 0.

309

0.36

6 0.

192

1.25

7 0.

456

0.57

9 0.

594

0.33

1 0.

375

0.23

0 0.

155

0.15

7 0.

216

Fe3+

0.

699

0.64

8 0.

602

0.41

2 0.

643

0.59

8 0.

935

1.19

7 1.

050

1.00

4 1.

113

1.24

3 1.

236

1.17

3 1.

219

Ti

0.13

5 0.

167

0.14

2 0.

198

0.21

1 0.

164

0.15

3 0.

172

0.15

0 0.

163

0.16

4 0.

117

0.13

5 0.

140

0.11

3 M

g 2.

608

2.53

1 2.

576

2.65

3 2.

484

2.65

2 2.

638

3.02

8 2.

887

3.24

4 3.

038

3.06

3 3.

052

2.83

5 3.

109

Fe2+

0.

845

0.90

1 1.

319

1.37

1 1.

425

0.32

9 0.

793

0.02

4 0.

291

0.25

8 0.

310

0.27

4 0.

351

0.63

0 0.

301

Mn

0.04

4 0.

000

0.05

1 0.

000

0.04

4 0.

000

0.02

5 0.

000

0.02

7 0.

000

0.00

0 0.

072

0.07

1 0.

065

0.04

2 C

5.

000

5.00

0 5.

000

5.00

0 5.

000

5.00

0 5.

000

5.00

0 5.

000

5.00

0 5.

000

5.00

0 5.

000

5.00

0 5.

000

Ca

1.82

8 1.

785

1.83

4 1.

957

2.00

0 1.

247

1.99

1 1.

462

1.51

1 1.

950

1.92

4 1.

601

1.69

0 1.

744

1.65

9 N

a 0.

172

0.21

5 0.

166

0.04

3 0.

000

0.75

3 0.

009

0.53

8 0.

489

0.05

0 0.

076

0.39

9 0.

310

0.25

6 0.

320

B

2.00

0 2.

000

2.00

0 2.

000

2.00

0 2.

000

2.00

0 2.

000

2.00

0 2.

000

2.00

0 2.

000

2.00

0 2.

000

1.97

9 C

a 0.

000

0.00

0 0.

000

0.00

0 0.

023

0.00

0 0.

000

0.00

0 0.

000

0.00

0 0.

000

0.00

0 0.

000

0.00

0 0.

000

Na

0.22

4 0.

180

0.45

7 0.

620

0.34

7 0.

001

0.46

5 0.

137

0.13

2 0.

119

0.24

2 0.

183

0.13

3 0.

177

0.00

0 K

0.

121

0.14

1 0.

096

0.18

2 0.

151

0.09

3 0.

130

0.00

0 0.

000

0.19

7 0.

132

0.11

1 0.

148

0.13

2 0.

135

A

0.34

5 0.

321

0.55

3 0.

802

0.52

1 0.

095

0.59

5 0.

137

0.13

2 0.

316

0.37

4 0.

294

0.28

0 0.

310

0.13

5 M

g#

0.75

5 0.

737

0.66

1 0.

659

0.63

5 0.

890

0.76

9 0.

992

0.90

8 0.

926

0.90

7 0.

918

0.89

7 0.

818

0.91

2

51

52

nesiohastingsite and tschermakite composition (Ta-ble 4, Fig. 4). There are occasional zonal crystals andsuch with opacitization rim. The monoclinic pyro-xene is augite up to diopside (after the classificationof Morimoto, 1988; Table 6). Occasional small or-thopyroxene (enstatite) phenocrysts are sometimescoated with clinopyroxene. Melt inclusions were alsoestablished in clinopyroxenes but less in comparisonwith those in amphiboles. In both of the cases, thesulfide melt inclusions were determined as pyrrhotite(Table 7) and chalcopyrite (optically) (Fig. 3B and 3C).

Small globular enclaves (with dimensions 2 mmto 4 cm) richer in pyroxene than the volcanic rockwere established in the groundmass of the pyroxene-amphibole basaltic andesites (Fig. 3D and 3E). Theyare probably remnants of more basic and primitivemantle-derived magma injected in the more evolvedlatitic melt in the intermediate chamber. Two typesof enclaves can be distinguished. The enclaves ofthe first type are composed of clinopyroxene (20 to60%), similar in composition to the phenocrysts inthe basaltic andesites (Table 6). Often the clinopy-roxene crystals are preferably located in the periph-ery of the enclave and were the first minerals to crys-tallize. The inner parts of the enclaves are sometimesmore fine-grained. Probably the mixing and minglingprocesses are responsible for the composition diver-sity of the amphiboles and the zonal arrangement ofsome phenocrysts. The second type enclaves are com-

Table 5Chemical composition (in wt. %) and mineral formulae of plagioclases (calculated at 8 oxygens) from volcanites of the Asarelvolcanic stripe (selected analyses)

Òàáëèöà 5Õèìè÷åí ñúñòàâ (â òåãë. %) è êðèñòàëîõèìè÷íè ôîðìóëè (ïðåèç÷èñëåíè êúì 8 êèñëîðîäà) íà ïëàãèîêëàçè îòâóëêàíñêè ñêàëè îò Àñàðåëñêàòà âóëêàíñêà èâèöà (èçáðàíè àíàëèçè)

Sample 30 BKX1 BKX1 BKX1 28 28 51 51' 51' Rock Lat BAn BAn BAn BAn BAn Bi An Bi An Bi An SiO2 63.88 55.86 50.98 66.35 51.99 55.87 57.33 61.97 57.69 TiO2 0.00 0.00 0.00 0.09 0.10 0.00 0.00 0.05 0.00 Al2O3 21.40 27.61 32.42 20.74 27.16 25.29 26.96 24.20 27.67 FeO 0.48 0.41 0.36 0.05 0.74 0.84 0.60 0.45 0.26 MnO 0.00 0.00 0.00 0.00 0.00 0.21 0.00 0.00 0.10 MgO 0.54 0.00 0.00 0.00 0.33 0.14 0.82 0.21 0.00 CaO 8.19 9.06 11.40 4.37 16.82 14.20 7.55 5.87 8.97 Na2O 5.49 6.64 4.71 6.81 2.08 2.80 5.51 6.47 4.87 K2O 0.13 0.00 0.11 0.55 0.55 0.16 0.91 0.79 0.35 BaO 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Total 100.11 99.58 99.98 99.36 99.77 99.51 99.68 100.01 99.91 Si 2.824 2.524 2.312 2.924 2.395 2.546 2.576 2.746 2.576 Ti 0.000 0.000 0.000 0.003 0.003 0.000 0.000 0.002 0.000 IVAl 1.114 1.469 1.731 1.076 1.474 1.357 1.426 1.263 1.455 Fe 0.018 0.017 0.014 0.017 0.029 0.032 0.023 0.017 0.010 Mn 0.000 0.000 0.000 0.000 0.000 0.008 0.000 0.000 0.004 Mg 0.036 0.000 0.000 0.000 0.023 0.010 0.055 0.014 0.000 Ca 0.388 0.439 0.554 0.206 0.830 0.693 0.363 0.279 0.429 Na 0.471 0.582 0.414 0.582 0.186 0.247 0.480 0.556 0.422 K 0.007 0.000 0.006 0.031 0.032 0.009 0.052 0.045 0.020 Ba 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 An 44.8 43.0 56.9 25.2 79.2 73.0 40.6 31.7 49.3 Ab 54.4 57.0 42.5 71.1 17.7 26.0 53.6 63.2 48.5 Or 0.8 0.0 0.6 3.8 3.1 1.0 5.8 5.1 2.3

Lat, latites; BAn, basaltic andesites; Bi An, biotite-amphibole andesites

Lat – ëàòèòè; BAn – àíäåçèòîáàçàëòè; Bi An – áèîòèò-àìôèáîëîâè àíäåçèòè

Fig. 4. Amphiboles of the magmatic rocks from the area ofthe Asarel porphyry copper deposit on the classificationdiagram from Leake et al., 1997¯ Pz Gr, Paleozoic granodiorites from the Smilovene luton;£ latites, amphibole latites to andesites; r bas. and, Px-Hbbasaltic andesites; Î Bi andesites, biotite-amphibole andesites

Ôèã. 4. Àìôèáîëè îò ìàãìåíèòå ñêàëè îò ðàéîíà íà Àñà-ðåë íàíåñåíè íà êëàñèôèêàöèîííàòà äèàãðàìà ïî Leakeet al., 1997¯ Pz Gr – ïàëåîçîéñêè ãðàíîäèîðèòè îò Ñìèëîâåíñêàòàèíòðóçèÿ; £ latites – àìôèáîëîâè ëàòèòè äî àíäåçèòè;r bas. and. – ïèðîêñåí-àìôèáîëîâè àíäåçèòîáàçàëòè;Î Bi andesites – áèîòèò-àìôèáîëîâè àíäåçèòè

Tab

le 6

Che

mic

al c

ompo

sitio

n (in

wt.

%)

and

min

eral

for

mul

ae o

f py

roxe

nes

(cal

cula

ted

at 6

oxy

gens

) fr

om b

asal

tic a

ndes

ites

and

mag

mat

ic e

ncla

ve o

f th

e Asa

rel vo

lcan

ic s

trip

e(s

elec

ted

anal

yses

)

Òàáë

èöà

6Õèì

è÷åí

ñúñ

òàâ

(â

òåã

ë. %

) è

êðèñ

òàë

îôõè

ìè÷

íè ô

îðì

óëè

(ïðå

èç÷è

ñëåí

è êú

ì 6

êèñ

ëîðî

äà)

íà ï

èðîê

ñåíè

îò

àíä

åçèò

îáàç

àëò

è è

ìàã

ìàò

è÷íî

âêë

þ÷å

íèå

îò À

ñàðå

ëñêà

òà

âóëê

àíñê

à èâ

èöà

BAn,

bas

alti

c an

desi

te; Enc

l., e

ncla

ve; c

ore,

cor

e of

the

min

eral

; ri

m,

rim

of

the

min

eral

BAn –

àíä

åçèò

îáàç

àëò;

Enc

l. –

ìàã

ìàò

è÷íî

âêë

þ÷å

íèå;

cor

e –

öåí

òðàë

íà ÷

àñò

íà ì

èíåð

àëà;

rim

– ï

åðèô

åðèÿ

íà

ìèí

åðàë

à

Sam

ple

28

28

BK

X1

BK

X1

25x

25x

25x

25x

44

bkx1

bk

x1

bkx1

bk

x1

Roc

k B

An

BA

n B

An

BA

n B

An

BA

n B

An

BA

n B

An

BA

n B

An

Encl

. En

cl.

Loca

tion

core

rim

rim

co

re

Cpx

O

px

core

rim

in

Hb

rim

core

rim

co

re

SiO

2 49

.77

53.6

9 55

.44

49.5

7 54

.62

55.7

7 51

.51

53.8

9 50

.21

53.2

0 53

.45

54.0

0 54

.78

TiO

2 0.

44

0.11

0.

22

0.10

0.

24

0.04

0.

20

0.31

0.

68

0.46

0.

51

0.41

0.

39

Al 2O

3 3.

30

2.11

5.

52

4.64

2.

48

2.44

2.

84

3.01

5.

54

3.94

3.

61

3.30

2.

91

FeO

10

.65

8.74

6.

36

9.79

7.

88

13.1

1 8.

09

9.17

9.

77

8.06

8.

12

7.96

7.

99

Cr 2

O3

0.00

0.

15

0.00

0.

00

0.00

0.

00

0.00

0.

00

0.00

0.

00

0.00

0.

00

0.13

M

nO

0.68

0.

65

0.36

0.

57

0.80

0.

79

0.56

0.

85

0.56

0.

45

0.35

0.

56

0.34

M

gO

11.7

0 16

.23

14.1

6 13

.48

15.3

0 26

.46

15.0

5 16

.17

13.2

4 15

.39

15.8

2 16

.02

15.9

1 C

aO

22.5

1 17

.75

17.1

7 20

.76

18.7

2 1.

03

21.3

2 16

.22

19.8

4 17

.43

17.5

6 17

.50

18.0

3 N

a 2O

0.

36

0.00

0.

00

0.57

0.

00

0.00

0.

00

0.00

0.

00

0.79

0.

58

0.00

0.

00

K2O

0.

00

0.00

0.

00

0.00

0.

00

0.00

0.

00

0.00

0.

12

0.00

0.

00

0.00

0.

00

Tota

l 99

.41

99.4

3 99

.23

99.4

8 10

0.04

99

.64

99.5

7 99

.62

99.9

6 99

.72

100

99.6

5 10

0.48

Si

1.

883

1.99

9 2.

068

1.84

9 2.

026

2.01

2 1.

916

2.00

4 1.

876

1.96

2 1.

967

2.00

2 2.

018

IVA

l 0.

117

0.00

1 0.

000

0.15

1 0.

000

0.00

0 0.

084

0.00

0 0.

124

0.03

8 0.

033

0.00

0 0.

000

T

2.00

0 2.

000

2.06

8 2.

000

2.02

6 2.

012

2.00

0 2.

004

2.00

0 2.

000

2.00

0 2.

002

2.01

8 V

I Al

0.03

0 0.

091

0.24

2 0.

053

0.10

8 0.

104

0.04

1 0.

132

0.12

0 0.

133

0.12

3 0.

144

0.12

6 Ti

0.

013

0.00

3 0.

006

0.00

3 0.

007

0.00

1 0.

006

0.00

9 0.

019

0.01

3 0.

014

0.01

1 0.

011

Fe

0.29

7 0.

001

0.00

0 0.

194

0.03

9 0.

000

0.11

9 0.

000

0.12

3 0.

008

0.00

0 0.

000

0.00

0 C

r 0.

000

0.00

4 0.

000

0.00

0 0.

000

0.00

0 0.

000

0.00

0 0.

000

0.00

0 0.

000

0.00

0 0.

004

Mg

0.66

0 0.

901

0.75

2 0.

750

0.84

6 0.

895

0.83

5 0.

859

0.73

8 0.

846

0.86

2 0.

844

0.85

9 M

1 1.

000

1.00

0 1.

000

1.00

0 1.

000

1.00

0 1.

000

1.00

0 1.

000

1.00

0 1.

000

0.99

9 1.

000

Mg

0.00

0 0.

000

0.03

6 0.

000

0.00

0 0.

589

0.00

0 0.

037

0.00

0 0.

000

0.00

5 0.

041

0.01

4 Fe

0.

039

0.27

2 0.

198

0.11

1 0.

205

0.39

6 0.

133

0.28

5 0.

182

0.24

1 0.

250

0.24

7 0.

246

Mn

0.02

2 0.

020

0.01

1 0.

018

0.02

5 0.

024

0.01

8 0.

027

0.01

8 0.

014

0.01

1 0.

014

0.01

1 C

a 0.

912

0.70

8 0.

686

0.83

0 0.

744

0.04

0 0.

850

0.64

6 0.

794

0.68

9 0.

692

0.69

5 0.

711

Na

0.02

6 0.

000

0.00

0 0.

041

0.00

0 0.

000

0.00

0 0.

000

0.00

0 0.

056

0.04

1 0.

000

0.00

0 K

0.

000

0.00

0 0.

000

0.00

0 0.

000

0.00

0 0.

000

0.00

0 0.

006

0.00

0 0.

000

0.00

0 0.

000

Wo

47.2

5 37

.24

40.7

6 43

.61

40.0

1 2.

12

43.4

9 34

.85

42.8

2 38

.32

38.0

2 37

.74

38.6

3 En

34

.17

47.3

7 46

.78

39.4

0 45

.50

75.5

9 42

.72

48.3

3 39

.76

47.0

7 47

.66

48.0

7 47

.43

Fs

18.5

8 15

.39

12.4

6 17

.00

14.5

0 22

.29

13.7

9 16

.82

17.4

2 14

.61

14.3

2 14

.18

13.9

4 M

g#

0.66

0.

77

0.80

0.

71

0.78

0.

79

0.77

0.

76

0.71

0.

77

0.78

0.

78

0.78

53

54

posed almost entirely of clinopyroxenes with occa-sional single plagioclase and biotite crystals (Fig. 3D).

Biotite-amphibole andesites, latites to dacites. Therocks are massive with porphyritic texture, gray todark-grey color, and microlitic to felsitic ground-mass. There are amphibole, biotite, plagioclase andrare quartz and magnetite phenocrysts. The accesso-ries are magnetite, apatite, zircon and small occa-sional primary pyrrhotite crystals trapped in amphib-oles (Fig. 8). Rounded xenoliths (light grey) and en-claves (dark-grey) were established in the biotite-amphibole andesites. The xenoliths are amphiboleandesites and holocrystalline porphyritic rocks, com-posed essentially of plagioclase phenocrysts and smalleuhedral mafic minerals in the groundmass.

The plagioclase crystals are zoned (andesine tooligoclase – An49—12; Table 5). The amphibole is eu-hedral brown-green tschermakite and magnesiohorn-blende, often altered and occasionally opacitized. Insome amphibole phenocrysts, melt inclusions withgaze bubbles were established. The biotite is euhe-dral to round and is often slightly chloritized andsometimes prenite is accommodated between the bi-otite flakes. The biotite includes plagioclase, magne-tite and zircon crystals, and is found included inamphibole in its turn. There are occasional roundedor irregularly shaped quartz phenocrysts with ground-mass bays, resulting probably from corrosion in themagmatic stage.

The differentiated Upper Cretaceous Asarel por-phyritic intrusion is composed of three phases. Someof the petrographic peculiarities of the plutonic por-

phyrites (e.g. dimensions and composition of thephenocrysts association; fine-grained groundmass)are similar to those in the biotite-amphibole andes-ites, established also by Popov et al. (2000). The sub-volcanic to hypabyssal level of crystallization led tothe relative coarsening of the crystals of the ground-mass and the realization of minerals like quartz andK-feldspar. Every subsequent intrusive phase: 1) fineporphyritic Q-diorite to Q-monzonite; 2) Q-monzo-nite porphyries to granodiorite porphyres; 3) graniteporphyries, is smaller in volume compared to theprevious one. The phenocrysts dimensions and thepotassic feldspar quantity slightly increase from thefirst to the second intrusive phase.

The quartz-diorites and quartz-monzonites por-phyries have massive structure and porphyritic tex-ture. Phenocrysts up to 2.5 mm are presented by pla-gioclase, biotite, amphibole and occasional potassicfeldspar crystals. The groundmass, representing about40% of the rock, is composed of plagioclase, quartzand potassic feldspar. It is fine-grained, equigranu-lar, with allotriomorphic and micrographic (eutec-tic) texture, indicating water saturation conditionsat the end of the crystallization process. Accessoryminerals are titanomagnetite, apatite, and zircon.

The quartz-monzonite porphyries and granodioriteporphyries of the second phase are composed of pla-gioclase, amphibole, biotite and occasional K-feld-spar and quartz phenocrysts, and a groundmass ofquartz, potassic feldspar and less plagioclase (withidiomorphism of quartz relatively to feldspars). Ac-cessory minerals are apatite, ore minerals, titanite andzircon. Small miarolitic cavities (up to 2 mm) latelyfilled with secondary quartz were established in thegroundmass (Fig. 3F). The miarolitic cavities wereconsidered evidence for the volatile phase satura-tion in the magma (Candela, 1997). They wereformed in conditions of decompression leading tocoalescence of bubbles of volatile saturated melt, fol-lowed by exsolution process of volatile phase.

Granite porphyries occur as dyke-like bodies inthe NW part of the open pit mine. They are leuco-cratic with porphyritic texture. The phenocrysts arepresented by strongly corroded or skeletal quartz,euhedral plagioclase (oligoclase) and occasionalpotassic feldspar. The groundmass is fine-grainedallotriomorphic, composed of quartz, potassic feld-spar, plagioclase and occasional small biotite flakes.The alteration affecting the granite porphyry is veryweak and we presume that the dyke was probablyformed after the intensive hydrothermal activity andthe ore formation.

Chemical composition

The chemical analyses of the rocks from the Asarelmagmatic center are based on the freshest (less al-tered and unaltered) samples with LOI less than 2wt.% (Tables 9, 10 and 11). The trace element com-position of the rocks was determined by X-ray Fluo-rescence (22 elements – in Lausanne) and Atom

Table 7Chemical composition (in wt. %) of sulfide inclusions (pyrrhotite)in mineral phenocrysts from volcanic rocks of the Asarelvolcanic stripe

Òàáëèöà 7Õèìè÷åí ñúñòàâ (â òåãë. %) îò ñóëôèäíè âêëþ÷åíèÿ(ïèðîòèí) â ìèíåðàëè ôåíîêðèñòàëè îò âóëêàíñêè ñêàëèîò Àñàðåëñêàòà âóëêàíñêà èâèöà

Sample 30 30 30 BKX1 28

Rock Lat Lat Lat BAn BAn host mineral Hb Hb Hb CPx CPx

Fe 61.01 61.15 62.09 57.79 57.39 S 38.32 39.23 35.78 38.26 41.65 Cu 0.55 0.00 2.45 3.55 0.37

Ni 0.00 0.00 0.20 0.37 0.33

Total 99.9 100.38 100.51 99.96 99.73

Fe 0.914 0.895 0.996 0.867 0.791 S 1.000 1.000 1.000 1.000 1.000 Cu 0.007 0.000 0.035 0.047 0.005

Ni 0.000 0.000 0.003 0.005 0.004

Lat, latite; BAn, basaltic andesite; Hb, amphibole; CPx,clinopyroxene

Lat – ëàòèò; BAn – àíäåçèòîáàçàëò; Hb – àìôèáîë; CPx,êëèíîïèðîêñåí

55

Table 8Chemical composition (in wt. %) and mineral formulae (calculated at 32 oxygens) for magnetites and titanomagnetites fromvolcanic rocks of the Asarel volcanic stripe

Òàáëèöà 8Õèìè÷åí ñúñòàâ (â òåãë. %) è êðèñòàëîõèìè÷íè ôîðìóëè (ïðåèç÷èñëåíè íà áàçàòà íà 32 êèñëîðîäà) íà ìàãíåòèòèè òèòàíîìàãíèòèòè îò âóëêàíñêèòå ñêàëè íà Àñàðåëñêàòà âóëêàíñêà èâèöà

Lat, latite; BAn, basaltic andesite; Bi-An, biotite-amphibole andesite; Mt, magnetite; Ti-Mt, titano-magnetite; gm, groundmass; Hb, amphibole; Cpx, clinopyroxene

Lat – ëàòèòè; BAn – àíäåçèòîáàçàëòè; Bi-An – áèîòèò-àìôèáîëîâè àíäåçèòè; Mt –ìàãíåòèò; Ti-Mt – òèòàíîìàãíåòèò;gm – îñíîâíà ìàñà; Hb – àìôèáîë; Cpx – êëèíîïèðîêñåí

Fig. 5. TAS classification diagram (Le Maitre et al., 1989) for the volcanic rocks from the Asarel volcanic stripe

Ôèã. 5. TAS êëàñèôèêàöèîííà äèàãðàìà (ïî Le Maitre et al., 1989) çà âóëêàíñêèòå ñêàëè îò Àñàðåëñêàòàâóëêàíñêà èâèöà

Sample 30 30 44 44 44 28 51' 51' Rock Lat Lat BАn BАn BАn BАn Bi-An Bi-An mineral Mt Mt Ti-Mt Ti-Mt Ti-Mt Ti-Mt Ti-Mt Ti-Mt Location in gm in gm in Hb in gm in Cpx in gm in Hb in Bi SiO2 3.95 1.88 0.66 0.42 0.57 0.65 0.29 0.52 TiO2 0.12 1.28 7.34 10.37 9.79 6.49 5.83 6.18 Al2O3 0.00 0.00 4.24 2.69 3.69 4.15 1.77 1.82 V2O5 0.20 0.00 0.00 0.00 0.00 0.00 0.00 0.00 FeO 88.76 88.44 78.02 77.18 78.21 80.51 83.3 85.54 MnO 0.00 0.00 0.99 0.81 0.57 1.12 1.06 0.52 MgO 0.00 0.00 2.41 1.48 1.47 0.96 1.8 0.00 CaO 0.37 0.30 0.15 0.18 0.17 0.17 0.00 0.19 Total 93.41 91.91 93.84 93.18 94.50 94.08 94.08 94.80 Si 1.20 0.59 0.20 0.13 0.17 0.19 0.09 0.16 Ti 0.03 0.30 1.64 2.37 2.19 1.46 1.32 1.40 Al 0.00 0.00 1.48 0.96 1.30 1.46 0.63 0.65 V 0.05 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Fe3+ 13.49 14.23 10.86 10.04 9.98 11.23 12.57 12.23 Fe2+ 9.11 8.78 8.47 9.56 9.51 8.89 8.33 9.37 Mn 0.00 0.00 0.25 0.21 0.14 0.28 0.27 0.13 Mg 0.00 0.00 1.06 0.67 0.65 0.43 0.81 0.00 Ca 0.12 0.10 0.05 0.06 0.05 0.05 0.00 0.06 Total 24.00 24.00 24.00 24.00 24.00 24.00 24.00 24.00 Ulv 14.97 10.73 23.42 31.47 30.12 21.12 17.40 19.39

56

Table 9Major (in wt. %) and trace element (in ppm) composition of intrusive rocks from the Smilovene pluton

Òàáëèöà 9Ãëàâíè ñêàëîîáðàçóâàùè îêñèäè (â òåãë. %) è åëåìåíòè ñëåäè (â ppm) íà èíòðóçèâíèòå ñêàëè îò Ñìèëîâåíñêèÿïëóòîí

Gd, granodiorite; Gr, granite; PegmGr, granitic pegmatite; Gb, gabbro

Gd – ãðàíîäèîðèò; Gr – ãðàíèò; PegmGr – ãðàíèòåí ïåãìàòèò; Gb – ãàáðî

Absorption Analysis (in Sofia University “St. KlimentOhridski” – 9 elements). REE were analyzed withICP-AES in the University of Geneva.

The studied volcanites are plotted on the TAS di-agram (Fig. 5) of Le Maitre et al. (1989). The pluton-ic rocks from the Paleozoic Smilovene pluton andthe Asarel porphyritic intrusions are plotted on a TAS

classification diagram for intrusive rocks (Fig. 6)(Magmatic …, 1983).

The Smilovene plutonic rocks are characterizedby 7 chemical analyses (Table 9). They plot as gran-odiorites and granites (Fig. 6), of the calc-alkaline(CA) to high-potassium calc-alkaline (HKCA) se-ries (after the diagram of Peccerillo and Taylor, 1976

Sample 38a 15 17a 40 AC 317 39 As-318 Rock Gd Gd Gd Gr Gr PegmGr Gb SiO2 67.36 65.71 66.95 71.05 69.83 73.18 46.33 TiO2 0.58 0.60 0.58 0.34 0.40 0.04 1.27 Al2O3 13.59 13.78 13.61 14.78 15.60 13.68 17.65 Fe2O3 0.78 1.16 0.70 0.03 0.64 1.05 6.82 FeO 3.58 3.73 3.55 1.41 1.44 7.97 MnO 0.22 0.09 0.09 0.06 0.04 0.02 0.45 MgO 2.65 2.97 2.75 0.83 1.06 0.23 7.87 CaO 2.38 4.29 5.06 3.04 2.38 0.25 1.00 Na2O 3.23 2.99 3.13 4.83 4.15 1.54 0.11 K2O 2.91 3.03 2.38 2.25 2.76 9.15 1.99 P2O5 0.34 0.24 0.30 0.13 0.08 0.12 0.17 H2O- 0.07 0.09 0.10 0.11 0.10 0.06 H2O+ 1.86 0.95 1.06 0.90 0.85 0.28 8.03 Total 99.55 99.63 100.26 99.76 99.33 99.54 99.72 Nb 8 7 10 5 7 4 Zr 100 94 117 60 58 30 Y 15 9 24 8 10 7 Sr 295 316 243 529 351 77 U 2 <2 <2 3 5 10 Li 13 19 7 3 3 27 Rb 84 113 111 70 93 202 106 Th 13 12 13 3 12 5 Pb 32 62 19 24 31 6 82 Ga 17 18 17 18 18 4 Zn 140 81 119 35 28 70 323 Cu 92 21 19 11 14 69 190 Ni 12 25 26 4 5 2 484 Co 5 13 15 3 3 <2 24 Cr 58 88 108 22 225 1 257 V 65 103 104 20 22 10 Ce 46 45 49 27 43 19 Nd 14 20 22 9 19 8 Ba 1312 746 660 857 970 849 La 25 29 29 11 24 6 Hf 6 4 7 5 5 5 Sc 10 15 9 6 8 <2 La 26.3 30.1 20.3 15.8 18.2 4.4 20.8 Ce 53.1 59 45.5 29.4 38.1 7.5 53.7 Pr 5.8 5.9 4.7 3.1 4.6 0.9 7.6 Nd 21.8 23.4 19.3 13.2 19.5 4.4 36.7 Sm 4.1 4.6 4 2.5 4.5 1.3 8.7 Eu 0.85 0.98 0.99 0.84 0.79 0.33 1.06 Gd 2.7 3.2 3.6 1.5 2.1 1.7 7 Dy 2.6 3 3.8 1.2 1.6 2.2 7.5 Ho 0.55 0.66 0.78 0.26 0.36 0.52 1.31 Er 1.4 1.7 2.2 0.7 1 1.5 3.4 Tm 0.22 0.24 0.32 0.12 0.12 0.21 0.56 Yb 1.2 1.4 1.9 0.7 1 1.5 3.6 Lu 0.17 0.21 0.27 0.1 0.14 0.22 0.44

57

Table 10Major (in wt. %) and trace element (in ppm) composition of volcanic rocks from the Asarel volcanic stripe

Òàáëèöà 10Ãëàâíè ñêàëîîáðàçóâàùè îêñèäè (â òåãë. %) è åëåìåíòè ñëåäè (â ppm) íà âóëêàíñêè ñêàëè îò Àñàðåëñêàòà âóëêàíñêàèâèöà

Lat, latite; BAn, basaltic andesite; Bi-An, biotite-amphibole andesite; Dac, dacite

Lat – ëàòèòè; BAn – àíäåçèòîáàçàëòè; Bi-An – áèîòèò-àìôèáîëîâè àíäåçèòè; Dac – äàöèòè

Sample 30 177 BKX1 187 187A 181(12) 51 174 176(1) Rock Lat Lat BAn BAn BAn Bi An Bi-An Dac Dac SiO2 56.71 58.02 55.55 55.87 52.05 59.68 59.76 63.31 64.33 TiO2 0.69 0.78 1.07 0.78 1.26 0.67 0.66 0.75 0.70 Al2O3 17.01 17.47 16.29 17.30 17.41 16.59 16.33 15.53 16.16 Fe2O3 3.30 4.20 4.96 5.40 4.44 3.06 2.55 2.80 3.10 FeO 3.29 2.61 3.36 3.54 4.80 2.60 2.90 2.47 2.01 MnO 0.17 0.10 0.21 0.11 0.22 0.15 0.12 0.14 0.13 MgO 3.43 2.44 3.85 4.02 5.16 3.44 3.81 2.32 1.78 CaO 4.08 6.50 8.68 5.03 6.17 4.25 3.95 4.98 5.01 Na2O 5.26 3.28 3.26 3.49 3.32 2.91 4.31 2.55 4.54 K2O 3.32 2.60 0.61 2.33 2.45 3.70 2.77 3.13 0.54 P2O5 0.40 0.26 0.29 0.37 0.22 0.25 0.18 0.33 0.26 H2O- 0.18 0.22 0.18 0.14 0.25 0.31 0.29 0.08 0.09 H2O+ 1.84 1.31 1.39 2.02 1.95 2.09 2.17 1.60 0.93 Total 99.68 99.79 99.70 100.40 99.70 99.70 99.80 99.99 99.58 Nb 7 7 8 9 6 7 Zr 142 140 162 141 115 103 Y 26 24 29 26 20 22 Sr 1042 715 814 604 517 681 U <2 <2 2 <2 <2 <2 Li 7 5 12 10 10 8 8 10 Rb 29 60 11 46 23 56 77 51 11 Th <2 4 2 6 8 4 Pb 7 16 10 15 8 15 59 6 17 Ga 19 19 20 22 18 15 Zn 76 72 96 83 101 180 72 103 73 Cu 34 25 40 38 51 23 51 37 22 Ni 5 9 12 10 73 5 3 <5 9 Co 4 19 21 19 19 7 16 7 14 Cr 25 40 51 72 33 47 18 63 146 V 162 180 239 236 143 168 Ce 42 42 38 61 56 Nd 23 25 22 31 21 12 Ba 36 616 578 633 70 375 La 32 21 21 32 36 10 Hf 9 8 11 7 7 6 Sc 5 13 28 19 20 12 La 21.2 21.6 23.3 Ce 47.7 48.6 49.1 Pr 5.6 5.8 5.8 Nd 25.9 26.9 22.8 Sm 5.3 5.5 4.6 Eu 1.41 1.55 1.12 Gd 4.3 4.6 3.3 Dy 3.9 4.6 2.9 Ho 0.79 0.99 0.64 Er 2.3 2.6 1.7 Tm 0.34 0.38 0.26 Yb 2.1 2.2 1.6 Lu 0.32 0.31 0.23

– not shown in this study). The Harker diagramsindicate fractionation of amphibole, plagioclase,magnetite and apatite. Decrease in TiO2, Fe2O3+FeO,MgO, CaO and P2O5, and increase in Na2O and K2Ocontent are observed with the Paleozoic magmatic

evolution (Fig. 7). The values of Al2O3 stay relativelyconstant. A decrease is established for Cr, Ni, Co, V,Zn, Rb, Sr, Zr, Y and Pb according to the SiO2 –trace element diagrams (Fig. 8). Cu and Ba contentsare relatively constant.

8 Ñïèñàíèå íà Áúëãàðñêîòî ãåîëîãè÷åñêî äðóæåñòâî, êí. 1—3, 2007

58

Table 11Major (in wt. %) and trace element (in ppm) composition of Upper Cretaceous intrusive porphyritic rocks from the Asarel pluton

Òàáëèöà 11Ãëàâíè ñêàëîîáðàçóâàùè îêñèäè (â òåãë. %) è åëåìåíòè ñëåäè (â ppm) íà ïîðôèðíè èíòðóçèâíèòå ñêàëè îò ãîðíîêðåäíèÿÀñàðåëñêè ïëóòîí

Qdp, quartz diorite porphyry; QMp, quartz monzonitic porphyry; Gdp, granodiorite porphyry; Grp, granite porphyry; Intr.phase, intrusive phase

Qdp – êâàðöäèîðèòîâ ïîðôèðèò; QMp – êâàðöìîíöîíèòîâ ïîðôèðèò; Gdp – ãðàíîäèîðèò ïîðôèð; Grp – ãðàíèòïîðôèð; Intr. phase – èíòðóçèâíà ôàçà

Sample AC 313 A 38* 310 B 180(2) 314 310 A 180(1) Intr. phase I I II II III III III Rock Qdp QMp QMp Gdp Grp Grp Grp SiO2 59.13 57.61 61.29 63.15 69.48 71.49 75.33 TiO2 0.70 0.73 0.55 0.56 0.40 0.12 0.14 Al2O3 17.24 15.63 16.76 15.90 14.74 14.56 12.77 Fe2O3 3.30 2.49 2.43 2.62 0.27 0.63 0.58 FeO 3.20 4.22 2.22 1.81 1.26 1.10 0.78 MnO 0.13 0.21 0.25 0.17 0.03 0.07 0.04 MgO 3.05 2.69 2.56 1.91 2.66 1.24 0.31 CaO 5.22 5.77 4.84 5.03 2.30 2.10 1.90 Na2O 4.14 3.88 2.86 3.09 4.50 2.63 3.41 K2O 2.56 2.70 4.63 3.34 1.43 4.43 3.48 P2O5 0.27 0.39 0.20 0.25 0.14 0.11 0.09 H2O- 0.24 0.10 0.16 0.17 0.38 0.14 0.13 H2O+ 1.35 3.32 1.46 1.70 1.88 1.07 0.67 Total 100.53 99.74 100.20 99.70 99.47 99.69 99.63 Nb 7 8 5 9 8 9 Zr 121 140 98 77 99 62 Y 24 21 20 15 11 9 Sr 526 399 539 264 318 257 Rb 75 88 132 56 56 170 106 Th 6 7 10 22 17 14 Pb 17 11 43 15 24 21 14 Ga 20 18 18 19 15 12 Zn 79 69 196 180 30 93 36 Cu 63 27 129 23 1641 62 11 Ni 10 8 6 5 15 6 3 Co 14 13 11 7 7 5 5 Cr 157 37 110 47 314 191 109 V 181 162 133 94 48 23 Ce 46 44 46 55 43 41 Nd 22 23 23 17 11 17 Ba 683 720 1394 411 880 968 La 26 27 28 27 26 16 Hf 7 5 7 18 8 8 Sc 16 10 6 12 2 <2 La 24.9 Ce 51.8 Pr 5.9 Nd 24.1 Sm 4.3 Eu 1.21 Gd 3.2 Dy 3.1 Ho 0.67 Er 1.8 Tm 0.26 Yb 1.6 Lu 0.24

Volcanic rocks from ASV are characterized by 7relatively unaltered samples (Table 10; Fig. 5). Theyplot essentially as HKCA series and less as CA, andshoshonitic (Sh) series. The intrusive porphyritic rocks(Table 11) plot as HKCA series. On the Harker dia-

grams for volcanites and porphyritic intrusives (Fig. 7and 8), concomitant with an increase of SiO2 con-tent is a decrease in TiO2, Al2O3, FeO+Fe2O3, MgO,CaO and P2O5, and an increase in K2O. Na2O con-tent is relatively constant. This is paralleled with a

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Fig. 6. Classification diagram SiO2 –(Na2O+K2O) for the plutonic rock of the re-gion of the Asarel porphyry copper deposit(after Magmatic……, 1983)Ç, Paleozoic granitoides of the Smilovene pluton;ö, gabbro (xenoblock in Paleozoic granitoides);Î, Upper Cretaceous porphiritic intrusive rocksof the Asarel intrusion

Ôèã. 6. Êëàñèôèêàöèîííà äèàãðàìà SiO2– (Na2O+K2O) çà èíòðóçèâíèòå ñêàëè îòìåäíî-ïîðôèðíî íàõîäèùå Àñàðåë (äèà-ãðàìàòà å ïî Magmatic……, 1983)Ç – ïàëåîçîéñêè ãðàíèòîèäè íà Ñìèëîâåí-ñêèÿ ïëóòîí; ö – ãàáðî (êñåíîáëîê â ïà-ëåîçîéñêèòå ãðàíèòîèäè); Î – ãîðíîêðåä-íè èíòðóçèâíè ïîðôèðíè ñêàëè îò Àñàðåë-ñêàòà èíòðóçèÿ

Fig. 7. Harker diagrams of the major oxides of the magmatic rocks in the region of the Asareldeposit¯, Upper Cretaceous volcanites of the Asarel volcanic stripe; r, Upper Cretaceous intrusiveporphyritic rocks of the Asarel pluton; É, Paleozoic granitoides of the Smilovene pluton

Ôèã. 7. Õàðêåðîâè äèàãðàìè íà ãëàâíèòå îêñèäè íà ìàãìåíèòå ñêàëè îò ðàéîíà íà íàõî-äèùå Àñàðåë¯ – ãîðíîêðåäíè âóëêàíèòè îò Àñàðåëñêàòà âóëêàíñêà èâèöà; r – ãîðíîêðåäíè èí-òðóçèâíè ñêàëè îò Àñàðåëñêèÿ ïëóòîí; É – ïàëåîçîéñêè ãðàíèòîèäè îò Ñìèëîâåíñêèÿïëóòîí

60

decrease in Ni, Co, V, Sr, Zr, Y and Pb, and increasein Rb. The tendencies for Cr and Ba are not so clear.The trace element content pattern is often more scat-tered for the porphyrites.

The chondrite-normalized REE distribution patterns(Fig. 9a—d) for the Hb andesites and latites (Lan/Ybn =

6.8), Px-Hb basaltic andesites (Lan/Ybn = 7.4—8.7),and Bt-Hb andesites (Lan/Ybn = 9.8—10.2) are char-acterized by enrichment in LREE, lack of negativeEu anomaly, and a successive increase in Lan/Ybnratio parallel to the magmatic evolution. This is maybe due to fractionation of pyroxenes and amphiboles

Fig. 8. Trace element Harker diagrams of the magmatic rocks from the region of the Asarel deposit¯, Upper Cretaceous volcanites of the Asarel volcanic stripe; r, Upper Cretaceous intrusive porphyriticrocks of the Asarel pluton; É, Paleozoic granitoides of the Smilovene pluton

Ôèã. 8. Õàðêåðîâè äèàãðàìè íà åëåìåíòè ñëåäè íà ìàãìåíè ñêàëè îò ðàéîíà íà íàõîäèùåÀñàðåë¯ – ãîðíîêðåäíè âóëêàíèòè îò Àñàðåëñêàòà âóëêàíñêà èâèöà; r – ãîðíîêðåäíè èíòðóçèâíèñêàëè îò Àñàðåëñêèÿ ïëóòîí; É – ïàëåîçîéñêè ãðàíèòîèäè îò Ñìèëîâåíñêèÿ ïëóòîí

Cr

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Fig. 9. Chondrite normalized patterns of the REE of the magmatic rocks from the area of the Asarel deposita, amphibole latites to andesites; b, basaltic andesites; c, biotite-amphibole andesites; d, Upper Cretaceousporphyritic plutonic rocks (porphyritic quartz-monzonite); e, granodiorites from the Paleozoic Smilovene pluton;f, granites from the Smilovene pluton; g, pegmatite from the Smilovene pluton

Ôèã. 9. Õîíäðèò-íîðìàëèçèðàíè ñïåêòðè íà ðàçïðåäåëåíèå íà ðåäêè è ðàçñåÿíè åëåìåíòè çà ìàãìåíè-òå ñêàëè îò ðàéîíà íà íàõîäèùå Àñàðåëà – àìôèáîëîâè ëàòèòè äî àíäåçèòè; b – àíäåçèòîáàçàëòè; c – áèîòèò-àìôèáîëîâè àíäåçèòè; d –ãîðíîêðåäíè èíòðóçèâíè ïîðôèðíè ñêàëè (ïîðôèðåí êâàðöîâ ìîíöîíèò); e – ãðàíîäèîðèòè îò ïàëåî-çîéñêèÿ Ñìèëîâåíñêè ïëóòîí; f – ãðàíèòè íà Ñìèëîâåíñêèÿ ïðóòîí; g – ïåãìàòèòè íà Ñìèëîâåíñêèÿïëóòîí

without plagioclase fractionation. The distributionpattern for the first phase of the porphyritic intrusion(Fig. 9d) is similar to those for the Bt-Hb andesites.

The chondrite-normalized REE distribution pat-terns for the Paleozoic granitoides (Fig. 9e—g) arecharacterized with a slight negative Eu anomaly andsteeper distribution specter compared to the Senon-ian magmatic rocks of Asarel. The Lan/Ybn ratio for

the granodiorites varies between 7.2 and 14.7 andthey have relatively higher REE contents. For thegranites, Lan/Ybn ratio varies between 12.2 and 15.2.The chondrite normalized distribution of the peg-matite is flat (Lan/Ybn = 2) with better expressed neg-ative Eu anomaly, indicating probably a fraction-ation of accessory minerals and feldspar before thesegregation of the pegmatite melt.

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Fig. 10. Rb – Y+Nb discrimination diagram for the tectonicsetting for granitoides (after Pearce et al., 1984) in the regionof the Asarel depositA, Pz GD (crosses); the open diamond ploting in the syn-collisional area is from a granite aplite; B, Upper Cretaceouporphyritic granitoidesSyn-COLG, syn-collisional granites; VAG, volcanic arcgranites; WPG, within plate granites; ORG, ocean ridgegranites

Ôèã. 10. Rb – Y+Nb äèñêðèìèíàöèîííè äèàãðàìè çà òåê-òîíñêàòà ïîçèöèÿ íà ãðàíèòîèäèòå (ïî Pearce et al.,1984) îò ðàéîíà íà íàõîäèùå ÀñàðåëA – ïàëåîçîéñêè ãðàíîäèîðèòè (êðúñò÷åòà) íà Ñìèëî-âåíñêàòà èíòðóçèÿ; ðîìá÷åòî, ïîïàäàùî â ïîëåòî íà ñèí-êîëèçèîííèòå ãðàíèòè, å îò ãðàíèò-àïëèòè; B – ãîðíî-êðåäíè ïîðôèðíè ãðàíèòîèäèSyn-COLG – ñèíêîëèçèîííè ãðàíèòè; VAG – îñòðîâíîäúãîâè ãðàíèòè; WPG – âúòðåøíîïëî÷îâè ãðàíèòè; ORG– îêåàíñêî-ðèôòîâè ãðàíèòè

Fig. 11. Chondrite normalized spidergrams of the volcanitesfrom the Asarel VSa, Hb latites; b, basaltic andesitesp; ñ, Bi-Hb andesites. Nor-malization values are from Thompson, 1982

Ôèã. 11. Õîíäðèò-íîðìàëèçèðàíè ñïàéäåðãðàìè çà âóë-êàíñêè ñêàëè îò Àñàðåëñêàòà âóëêàíñêà èâèöàà – Hb ëàòèòè; b – àíäåçèòî-áàçàëòè; ñ – Bi – Hb àíäåçè-òè. Ñòîéíîñòèòå çà íîðìàëèçàöèÿòà ñà ïî Thompson, 1982

cluding the Srednogorie Variscan intrusions, deter-mine it as post collisional (Haidoutov, 1991; Carrig-an et al., 2005).

Up to now, the views on the tectonic setting of theSenonian magmatism and the ore formation are verycontroversial. The calc-alkaline to shoshonitic char-acter of the magmatic rocks; the low Ti and Nb con-tent (negative anomalies in chondrite-normalizedspidergrams – Fig. 11); the volcaniclastic rocks pre-dominance; the presence of all the volcanic rocksfrom basaltic andesites to rhyolites and trachytes (inPanagyurishte region) support the view for subduc-tion related (volcanic arc or destructive continentalmargin) setting for the Srednogorie magmatism. Thediscrimination diagrams for the basaltic andesites(Fig. 12 – after Wood et al., 1980; Meshed, 1986)illustrate destructive plate margin setting for the Se-nonian volcanites from the Panagyurishte region,while the Senonian intrusive porphyrites plot in thefield of volcanic arc granites (Fig. 10B).

The discrimination diagram for island arc plu-tonic complexes (Kepezhinskas et al., 1991) (Fig. 13)shows conditions of normal to mature arc for boththe Paleozoic granodiorites and the Senonian por-phyrites.

Tectonic setting duringthe magmatic events

The granodiorites and granites of the Smilovene plu-ton are metaluminous with I-type characteristics. Theyplot in the field of volcanic arc granites (Fig. 10A) onthe Rb – (Y+Nb) discrimination diagram (Pearceet al., 1984). Previous investigations on the tectonicsetting of the Variscan plutonism in Bulgaria, in-

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Fig. 12. Tectonic setting of the Asarel VS volcanism after thediscrimination of basaltic andesitesA, (Th—Nb—Hf) discrimination diagram after Wood, 1980(A, normal mid ocean ridge basalts; B, enriched mid oceanridge basalts; C, within plate basalts; D, basalts from destruc-tive plate margins); B, (Zr—Y—Nb) discrimination diagramafter Meschede, 1986 (A, within plate basalts; B, primordialmid ocean ridge basalts; C, volcanic arc basalts; D, normalmid ocean ridge basalts)

Ôèã. 12. Îïðåäåëÿíå íà òåêòîíñêîòî ïîëîæåíèå íà âóë-êàíèçìà îò Àñàðåëñêàòà âóëêàíñêà èâèöà ïî õðàêòåðèñ-òèêèòå íà àíäåçèòîáàçàëòèòåÀ – (Th—Nb—Hf) äèñêðèìèíàöèîííà äèàãðàìà ïî Wood,1980 (A – íîðìàëíè ñðåäèííî-îêåàíñêè õðåáåòíè áàçàë-òè; B – íàáîãàòåíè ñðåäèííî-îêåàíñêè õðåáåòíè áàçàë-òè; C – âúòðåøíî-ïëî÷îâè áàçàëòè; D – áàçàëòè îò äåñ-òðóêòèâíèòå îêðàéíèíè íà ïëî÷èòå);  – (Zr—Y—Nb) äèñ-êðèìèíàöèîííà äèàãðàìà ïî Meschede, 1986 (A – âúò-ðåøíî-ïëî÷îâè áàçàëòè; B – ïðèìèòèâíè ñðåäèííî-îêå-àíñêè õðåáåòíè áàçàëòè; C – îñòðîâíî-äúãîâè áàçàëòè;D – íîðìàëíè ñðåäèííî-îêåàíñêè õðåáåòíè áàçàëòè)

Fig. 13. La versus Sm systematics. Fields for various settingsof plutonic complexes (after Kepezhinskas et al., 1991)Î, Upper Cretaceous porphiritic intrusive rocks of the Asarelintrusion; Ç, Paleozoic granitoides of the Smilovene Pluton

Ôèã. 13. Äèàãðàìà La – Sm äèñêðèìèíèðàùà çðåëîñòòàíà îñòðîâíî-äúãîâàòà ñèñòåìà (ïî Kepezhinskas et al.,1991)Î – ãîðíîêðåäíè ïîðôèðíè èíòðóçèâíè ñêàëè íà Àñà-ðåëñêàòà èíòðóçèÿ; Ç – ïàëåîçîéñêè ãðàíèòîèäè íà Ñìè-ëîâåíñêèÿ ïëóòîí

Termobarometry

The pressure during the crystallization process wasdetermined using the amphibole barometer ofJohnson and Rutherford (1989) based on the totalAl content in amphiboles. The temperatures of crys-tallization were estimated with the amphibole-pla-gioclase geothermometer of Blundy and Holland(1990) (Table 12). The two-pyroxene thermometer(Wells, 1970) estimates the temperature of crystalli-zation of the two-pyroxene equilibrium at 1160° C.The relatively high temperature of amphibole crys-tallization (up to 910° C) is probably due to the en-larged stability field of amphibole in the hydrousmagma. The early amphibole crystallization proba-bly occurred in a relatively deep (15—20 km) inter-mediate magmatic chamber. The Paleozoic grano-diorite intrusion crystallized at abyssal level of 4.5—6 kb (12—15 km) (after the Schmidt geobarometer,1992) and 760° C.

64

Conclusions

The magmatic evolution of the Asarel volcanism wasgoverned essentially by the mineral fractionation andthe magma mixing. The petrographic evidence forthe importance of the fractionation processes is thedecrease of pyroxene and amphibole content towardthe Bt-Hb andesites. The decrease in MgO, CaO,FeO+Fe2O3, TiO2, P2O5, Ni, Cr, Co, Sr and V duringthe evolution of the Senonian magmatism, paralleledwith the increase of Lan/Ybn ratio could be related tothe fractionation of clinopyroxene, amphibole, tita-nomagnetite and apatite. The lack of negative Euanomaly let us suppose that plagioclase was not in-volved in the fractionation. Calculations show thatthe fractionation alone is not able to define the dif-ferentiation. Magma mixing in different proportionsis a process that took place probably during the wholeinterval of volcanic activity in the Panagyurishte re-gion. The presence of small enclaves in the basalticandesites, magmatic corrosion of first generation pla-gioclase as well as reverse zoning in plagioclase arethe petrographic evidence for the importance of this

process. Moreover, this process was of essential im-portance for the formation of the Hb-Cpx basalticandesites from the second volcanic impulse. Intro-duction of more primitive magma in the intermedi-ate chamber is interpreted from many scientists asone of the most effective processes triggering volca-nic eruptions. The preserved small enclaves give usthe possibility to presume this more primitive magmawas close to pyroxenitic composition.

The small vacuoles and the graphic groundmassin the porphyritic rocks indicate the magma was rel-atively rich in water and reached water saturationduring the crystallization process.

The chondrite normalized diagrams (Fig. 11) forvolcanites show the typical for subduction relatedrocks negative Nb anomaly relative to K and La,paralleled with a positive Hf anomaly relative to Zrand Ti.

The ORG-normalized spider grams for the rocksof the Smilovene pluton show the typical signaturefor volcanic arc granitoid plutonism similar to thepatterns of the Jamaica granites (from Pearce et al.,1984).

According to the interpretations of Kamenov etal. (2004), magmas in the Asarel region were derivedfrom a metasomatized fertile MORB mantle, by 15—20% degree melting from a spinel lherzolitic sourcewith amphibole, phlogopite, apatite and rutile. Therelatively high degree of melting could also explainthe primitive pyroxenite-like enclaves in the basalticandesites.

Acknowledgements: We would like to thank for thefinancial support of this work the Fund of science in-vestigations of the Sofia University (research projectN679/2002) and for financial, analytical and scientif-ic support international projects NZ 03/2004 and VU-NZ 02/2005 of the National Foundation for ScientificInvestigations of the Ministry of Education and Sci-ence of Bulgaria, SCOPES – 7BUPJ02276.00/1 andABCD—GEODE. We would like to thank H. Stanchevfrom “Eurotest” and the laboratory of the University ofGeneva for the numerous microprobe analyses of rockforming minerals. We would like to express our grati-tude to the geological stuff of the Asarel deposit, espe-cially to L. Koprivshka for their help during the fieldwork.

Table 12T and P parameters of the crystallization of magmatic rocksfrom the Asarel area

Òàáëèöà 12Îöåíêà íà òåðìî-áàðè÷íèòå ïàðàìåòðè íà êðèñòàëèçà-öèÿòà íà ìàãìåíè ñêàëè îò ðàéîíà íà Àñàðåë

Presure for volcanic rocks determined after the geobarometerof Johnson, Rutherford (1989), for the granodiorites afterSchmidt (1992). Temperature – after the geothermometer ofBlundy, Holland (1990)

Íàëÿãàíåòî çà âóëêàíèòèòå å îïðåäåëåíî ÷ðåç ãåîáàðî-ìåòúðà íà Johnson, Rutherford (1989), à çà ãðàíîäèîðèòè-òå – Schmidt (1992). Òåìïåðàòóðàòà íà êðèñòàëèçàöèÿ åîïðåäåëåíà ïîñðåäñòâîì àìôèáîë-ïëàãèîêëàçîâèÿ ãåî-òåðìîìåòúð íà Blundy, Holland (1990)

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