Upper background thresholds. The values calculatedfor <strong>the</strong> upper background threshold(UBT 0.05) <strong>of</strong> <strong>the</strong> element <strong>contents</strong> (Tables 1 <strong>and</strong> 2)give a general idea <strong>of</strong> <strong>the</strong> upper limit <strong>of</strong> normalelement concentrations <strong>in</strong> <strong>the</strong> <strong>rocks</strong> most widelyspread <strong>in</strong> Bulgaria. Each rock group has its specificUBT for <strong>the</strong> <strong>in</strong>dividual <strong>elements</strong>, which may belower or higher than <strong>the</strong> respective total UBT forall <strong>the</strong> <strong>rocks</strong> (Table 1).The upper background threshold marks <strong>the</strong> limits<strong>of</strong> <strong>the</strong> normal concentrations. This value is first <strong>of</strong>all applicable for <strong>the</strong> rock groups, while for <strong>the</strong> totalpopulation <strong>of</strong> all <strong>rocks</strong> UBT has an approximatecharacter because <strong>of</strong> <strong>the</strong> element differentiationbetween <strong>rocks</strong> with different chemical <strong>and</strong> m<strong>in</strong>eralcomposition <strong>and</strong> different genesis. The total upperbackground threshold for all types <strong>of</strong> <strong>rocks</strong> comb<strong>in</strong>ed,applied to <strong>some</strong> rock types, would exclude apart <strong>of</strong> <strong>the</strong> background samples as anomalous, <strong>and</strong>for o<strong>the</strong>r types it would <strong>in</strong>clude anomalous samples<strong>in</strong>to <strong>the</strong> category <strong>of</strong> <strong>the</strong> background ones. Forexample, <strong>the</strong> total UBT for Ni is 106 ppm, but <strong>the</strong>UBT <strong>in</strong> <strong>the</strong> ultrabasic <strong>and</strong> basic <strong>rocks</strong> where <strong>the</strong>same element is concentrated are respectively 3610ppm <strong>and</strong> 192 ppm (Table 1).The width <strong>of</strong> <strong>the</strong> <strong>in</strong>terval between upper backgroundthreshold <strong>and</strong> mean content (C BG) is differentfor <strong>the</strong> <strong>in</strong>dividual <strong>elements</strong>. It depends on<strong>the</strong> variance <strong>of</strong> <strong>the</strong> background <strong>contents</strong>. Accord<strong>in</strong>gto <strong>the</strong> values <strong>of</strong> <strong>the</strong> ratio UBT 0.05/ C BG(Table 2)<strong>the</strong> <strong>elements</strong> considered form <strong>the</strong> follow<strong>in</strong>g order:Be 2.9 – Pb 3.0 – Ba 3.3 – Zn 3.4 – As 3.4 – Mn3.5 – Sr 3.6 – Sc 3.7 – Ti 4.5 – Co 4.9 – Mo 4.9 –Sn 4.9 – W 5.0 – V 5.2 – Cu 5.3 – Ni 6.2 – Cr 8.2– Hg 18.7.Exclud<strong>in</strong>g <strong>the</strong> endmost member <strong>of</strong> <strong>the</strong> row (Hg)<strong>the</strong> ratio UBT 0.05/ C BGvaries from 3 to 8, at an averageabout 4.On lower hierarchical levels (for example, forl<strong>and</strong>scapes, geological-structural or adm<strong>in</strong>istrativeregions, different rock complexes, etc.) <strong>the</strong> parameters<strong>of</strong> <strong>the</strong> background concentrations (mean content<strong>and</strong> upper background threshold) <strong>of</strong> <strong>the</strong> <strong>elements</strong>may have <strong>the</strong>ir specific local values, <strong>in</strong>cludedstatistically <strong>in</strong> <strong>the</strong> general estimates obta<strong>in</strong>ed for<strong>the</strong> whole Bulgarian territory.ConclusionThe reference values derived for <strong>the</strong> mean background<strong>contents</strong> <strong>of</strong> Be, Sr, Ba, Sc, Ti, V, Cr, Mo, W,Mn, Co, Ni, Cu, Zn, Hg, Sn, Pb <strong>and</strong> As may be acceptedas sufficiently reliable geochemical st<strong>and</strong>ards,characteris<strong>in</strong>g <strong>the</strong> chemical composition <strong>of</strong> <strong>the</strong> <strong>rocks</strong>on Bulgarian territory.The background values established are based onreal results from quantitative chemical analysespublished <strong>in</strong> Bulgarian geochemical studies dur<strong>in</strong>ga period <strong>of</strong> 40 years. In spite <strong>of</strong> <strong>the</strong> local representativity<strong>of</strong> <strong>the</strong> rock samples (for <strong>the</strong> country) <strong>the</strong> valuesderived show good co<strong>in</strong>cidence with <strong>the</strong> recentlycalculated averages <strong>of</strong> <strong>the</strong> studied <strong>elements</strong> <strong>in</strong> <strong>the</strong>upper cont<strong>in</strong>ental crust.The content <strong>of</strong> Cd <strong>in</strong> <strong>the</strong> <strong>rocks</strong> <strong>in</strong> Bulgaria needsadditional <strong>in</strong>vestigations <strong>and</strong> first <strong>of</strong> all – new dataobta<strong>in</strong>ed through highly sensitive modern analyticalmethods.The results obta<strong>in</strong>ed show that <strong>the</strong>re is no “ones<strong>in</strong>gle” background value for given element, whichcan be equally valid for all types <strong>of</strong> <strong>rocks</strong>. The <strong>in</strong>dividualrock groups are dist<strong>in</strong>guished with specificparameters <strong>of</strong> distribution <strong>of</strong> <strong>the</strong> background concentrations(mean value, variance, upper backgroundthreshold, etc.) which <strong>of</strong>ten are significantly differentfrom each o<strong>the</strong>r, especially for <strong>the</strong> <strong>contents</strong> <strong>of</strong><strong>the</strong> most <strong>in</strong>tensively differentiated <strong>elements</strong> – Hg,Cr, Ti, Ni, V, Cu <strong>and</strong> Co.The reference background values obta<strong>in</strong>ed for 18<strong>elements</strong> known as <strong>m<strong>in</strong>or</strong> <strong>and</strong> <strong>trace</strong> components <strong>in</strong><strong>the</strong> chemical composition <strong>of</strong> <strong>the</strong> <strong>rocks</strong> – Be, Sr, Ba,Sc, Ti, V, Cr, Mo, W, Mn, Co, Ni, Cu, Zn, Hg, Sn, Pb<strong>and</strong> As – may have a multipurpose application forcomparative geochemical, petrological, lithological<strong>and</strong> metallogenic <strong>in</strong>vestigations, for assessment <strong>of</strong> <strong>the</strong>quality <strong>of</strong> <strong>the</strong> environment (soils, etc.) <strong>and</strong> as regionalClarkes <strong>of</strong> <strong>the</strong>se <strong>elements</strong> for <strong>the</strong> Bulgarian territory<strong>and</strong> <strong>the</strong> Balkan region, as well.ReferencesChristova, J., Christov, D. 2006. <strong>Background</strong> <strong>contents</strong> <strong>of</strong> Be, Sr,Ba, Sc, Ti, V, Mo, W, Sn <strong>in</strong> <strong>the</strong> <strong>rocks</strong> <strong>in</strong> Bulgaria. – C. R.Acad. Bulg. Sci., 59, 2; 175—180.Darnley, A. G. 1995. Global geochemical database for environment<strong>and</strong> resource management: F<strong>in</strong>al report <strong>of</strong> IGSP projectNo 259. UNESCO; 122 p.Gao, S., Luo, T.-C., Zhang, B.-R., Zhang, H.-F., Han, Y.-W.,Hu, Y.-K., Zhao, Z.-D. 1998. Chemical composition <strong>of</strong> <strong>the</strong>cont<strong>in</strong>ental crust as revealed by studies <strong>in</strong> East Ch<strong>in</strong>a. –Geochim.&Cosmochim. Acta, 62, 11; 1959—1975.Kuik<strong>in</strong>, S., Christova, J., Christov, D. 2001. Mean concentrations<strong>of</strong> Cr, Mn, Co, Ni, Cu, Zn, As, Cd, Hg <strong>and</strong> Pb <strong>in</strong> <strong>the</strong><strong>rocks</strong> <strong>of</strong> Bulgaria. – C. R. Acad. Bulg. Sci., 54, 9; 63—68.Rudnick, R. L., Gao, S. 2003. Composition <strong>of</strong> <strong>the</strong> cont<strong>in</strong>entalcrust. – In: The Crust, Treatise on Geochemistry, v. 3,Elsevier – Pergamon, Oxford; 1—64.Tong, Li. 1995. Element abundances <strong>of</strong> Ch<strong>in</strong>a’s cont<strong>in</strong>entalcrust <strong>and</strong> its sedimentary layer <strong>and</strong> upper cont<strong>in</strong>ental crust.– Ch<strong>in</strong>ese J. <strong>of</strong> Geochemistry, 14, 1; 26—32.Turekian, K. K., Wedepohl, K. H. 1961. Distribution <strong>of</strong> <strong>the</strong><strong>elements</strong> <strong>in</strong> <strong>some</strong> major units <strong>of</strong> <strong>the</strong> Earth’s crust. – Bull.Geol. Soc. America, 72, 2; 175—192.Van de Meent, D., Aldenberg, T., Canton, J. H., von Gestel, C.A. M., Sto<strong>of</strong>f, W. 1990. Desire for levels. <strong>Background</strong> studyfor <strong>the</strong> policy document “Sett<strong>in</strong>g environmental qualityst<strong>and</strong>ard for water <strong>and</strong> soil”. – Engl. vers. from dutch,RIVM – report No 670101.001 – “Streven Naar Waarden”;52 p.Wedepohl, K. H. 1995. The composition <strong>of</strong> <strong>the</strong> cont<strong>in</strong>entalcrust. – Geochim.&Cosmochim. Acta, 59, 7; 1217—1232.Âåðíàäñêèé, Â. È. 1954. Èçáðàííûå ñî÷èíåíèÿ, ò. 1. Ìîñêâà,ÀÍ ÑÑÑÐ; 396—410; 519—527.74
Âèíîãðàäîâ, À. Ï. 1962. Ñðåäíåå ñîäåðæàíèå õèìè÷åñêèõýëåìåíòîâ â ãëàâíûõ òèïàõ èçâåðæåííûõ ãîðíûõ ïîðîäçåìíîé êîðû. – Ãåîõèìèÿ, 7; 555—571.Ãëóõàí, È. Â., Ñåðûõ, Â. È. 2000. Êëàðêè àëåâðîëèòîâ èàðãèëëèòîâ Öåíòðàëüíîãî Êàçàõñòàíà. – Ãåîõèìèÿ,9; 922—940.Êóéêèí, Ñ., Ïàíàéîòîâ, À., Êåðáåëîâà, Â., Êþ÷óêîâà, Ì.1979. Ðåãèîíàëíè çàêîíîìåðíîñòè â ðàçïðåäåëåíèåòîíà ìåäòà, öèíêà, îëîâîòî, ìîëèáäåíà è êàëàÿ â Ñòðàíäæà.– Ñï. Áúëã. ãåîë. ä-âî, 40, 2; 129—142.Îâ÷èííèêîâ, Ë. Í. 1990. – Ïðèêëàäíàÿ ãåîõèìèÿ. – Ìîñêâà,Íåäðà; 248 ñ.Ñòàíåâ, À., Ãàòåâ, Ê., Ìóòàôîâ, Í. 1971. Îáùà òåîðèÿ íàñòàòèñòèêàòà. – Âàðíà, Äúðæ. èçä.; 384 ñ.Þôà, Á. ß., Ãóðâè÷, Þ. Ì. 1964. Ïðèìåíåíèå ìåäèàíûè êâàðòèëåé äëÿ îöåíêè íîðìàëíûõ è àíîìàëüíûõçíà÷åíèé ãåîõèìè÷åñêîãî ïîëÿ. – Ãåîõèìèÿ, 8; 817—824.ßðîøåâñêèé, À. À. 1990. – Ñðåäíèå ñîäåðæàíèÿ ýëåìåíòîââ ãîðíûõ ïîðîäàõ. – Â: Ñïðàâî÷íèê ïî ãåîõèìè-÷åñêèì ïîèñêàì ïîëåçíûõ èñêîïàåìûõ (ðåä. À. Ï. Ñîëîâîâ).Íåäðà, Ìîñêâà; 19—24.Appendix 1Publications – sources <strong>of</strong> data for <strong>the</strong> <strong>contents</strong> <strong>of</strong> Be, Sr, Ba,Sc, Ti, V, Cr, Mo, W, Mn, Co, Ni, Cu, Zn, Cd, Hg, Sn, Pb <strong>and</strong> As<strong>in</strong> <strong>the</strong> <strong>rocks</strong> on Bulgarian territoryChatalov, A. 1995. – Ann. L’Univ. S<strong>of</strong>ia “St. Kl. Ohridski”,Fac. Geol. et Geogr., 1 – Geologie, 88; 97—130.Daieva, L., Kozhukharova, E. 1987. – Geol. Balcanica, 17, 6;25—30.Harkovska, A., Marchev, P., Machev, Ph., Pecskay, Z. 1988. –Acta vulcanol., 10, 2; 199—216.Haydoutov, I., Daieva, L., Kolcheva, K. 1993. – Rev. Bulg.geol. soc., 54, 3; 60—70.Haydoutov, I., P<strong>in</strong>, Chr. 1993. – Geol. Balcanica, 23, 6; 51—59.Kamenov, B., Peytcheva, I., Kla<strong>in</strong>, L., Arsova, K., Kostits<strong>in</strong>,Y., Salnikova, E. 1999. – Geochem., m<strong>in</strong>eral. <strong>and</strong> petrol.,36; 3—27.Kolčeva, K., Eskenazy, G. 1988. – Geol. Balcanica, 18, 5; 61—78.Kolcheva, K., Haydoutov, I., Daieva, L. 2000. – Geochem.,m<strong>in</strong>eral. <strong>and</strong> petrol., 37; 25—38.Kozhoukharova, E. 1999. – Geol. Balcanica, 29, 1—2; 89—109.Kozhoukharova, E., Daieva, L. 1990. – Geol. Balcanica, 20, 4;19—35.Machev, Ph., Kenkmann, T. 2001. – Rev. Bulg. geol. soc., 62,1—3; 65—76.Marchev, P., Rogers, G., Conrey, G. R., Quick, J., Vaselli, O.,Raicheva, R. 1998 1. – Acta vulcanol., 10, 2; 217—232.Marchev, P., Vaselli, O., Downes, H., P<strong>in</strong>arelli, L., Ingram, G.,Rogers, G., Raicheva, R. 1998 2. – Acta vulcanol., 10, 2;233—242.Nedialkov, R., Pe-Piper, G. 1998. – Acta vulcanol., 10, 2;243—253.Yanev, S. N. 1992. – Geol. Balcanica, 22, 2; 2—31.Yanev, Y. 1998. – Acta vulcanol., 10, 2; 265—277.Àêðàáîâ, Ã., Ãðúí÷àðîâ, Õð., Àðíàóäîâà, Ð., Ïàëèêîâ, Ñ.,Êðúñòåâ, Í., Ïåòðîâ, Ï. 1984. – Òð. Íàó÷íîèçñë. è-òïîë. èçêîï., 1; 201—221.Àëåêñèåâ, Å. 1960. – Òð. ãåîë. Áúëãàðèÿ, ñåð. ãåîõ. è ïîë.èçêîï., 1; 3—64.Àëåêñèåâ, Å. 1961. – Òð. ãåîë. Áúëãàðèÿ, ñåð. ãåîõ. è ïîë.èçêîï., 2; 253—317.Àëåêñèåâ, Å. 1965. – Êàðïàòî-Áàëê. ãåîë. àññ., VII êîíãðåñ,Ñîôèÿ, Äîêëàäû, ÷. III; 9—15.Àëåêñèåâ, Å. 1966. – Òð. ãåîë. Áúëãàðèÿ, ñåð. ãåîõ, ìèíåðàë.è ïåòðîãð., 6; 49—66.Àðíàóäîâ, Â., Ïàâëîâà, Ì., Àðíàóäîâà, Ð. 1975. – Ãåîõ.,ìèíåðàë. è ïåòðîë., 1; 68—78.Àðíàóäîâ, Â., Ïàâëîâà, Ì., Àðíàóäîâà, Ð. 1977. – Geol.Balcanica, 7, 2; 85—98.Àðíàóäîâ, Â., Áîÿäæèåâà, Ð., Êàðàèâàíîâà, Á. 1986. – Ãåîõ.,ìèíåðàë. è ïåòðîë., 22; 22—29.Àðíàóäîâà, Ð., Àðíàóäîâ, Â. 1982. – Geol. Balcanica, 12, 4;21—36.Àðíàóäîâà, Ð., Àðíàóäîâ, Â., Ïàâëîâà, Ì. 1971. – Èçâ.Ãåîë. è-ò, ñåð. ãåîõ., ìèíåð. è ïåòðîãð., 20; 5—20.Áàðñêà, Ñ. 1972. – Ñï. Áúëã. ãåîë. ä-âî, 33, 2; 153—163.Áåëèâàíîâà, Â. 1992. – Ñï. Áúëã. ãåîë. ä-âî, 53, 2; 35—46.Áåëìóñòàêîâà, Õ. 1984. – Ãåîõ., ìèíåðàë. è ïåòðîë., 18;56—83.Áåëìóñòàêîâà, Õ. 1995. – Ñï. Áúëã. ãåîë. ä-âî, 56, 1; 75—91.Áîÿäæèåâ, Ñ. 1986. – Ãåîõ., ìèíåðàë. è ïåòðîë., 20–21;97—129.Áîÿäæèåâ, Ñ. 1991. – Geol. Balcanica, 21, 3; 35—74.Áîÿäæèåâ, Ñ. 1993. – Ñï. Áúëã. ãåîë. ä-âî, 54, 2; 19—35.Áîÿäæèåâ, Ñ., Àëåêñèåâ, Å. 1970. – Èçâ. Ãåîë. è-ò, ñåð.ãåîõ., ìèíåð. è ïåòðîãð., 19; 17—33.Áîÿäæèåâ, Ñ., ×èï÷àêîâà, Ñ. 1963. – Ãîä. Ãëàâ. óïðàâë.ãåîë., 13; 5—71.Áîÿäæèåâ, Ñ., ×èï÷àêîâà, Ñ. 1965. – Èçâ. Íàó÷íîèçñë. ãåîë.è-ò, 2; 75—110.Âåëèíîâ, È. 1964. – Èçâ. Ãåîë. è-ò “Ñòð. Äèìèòðîâ”, 13;81—97.Âóòîâ, È. 1967. – Ãîä. Âèñø ìèííî-ãåîë. è-ò, 13, 5; 69—94.Ãåîðãèåâà, È. À. 1989. – Ñï. Áúëã. ãåîë. ä-âî, 50, 3; 99—112.Äà÷åâ, Ä., Áîðèñîâà, É. 2000. – Ãåîë. è ìèíåðàë. ðåñóðñè,1–2; 31—35.Äåë÷åâ, À., Äèìèòðîâ, Ñ. 1964. – Ãîä. Ãë. óïð. ãåîëîãèÿ, 15;5—34.Äèìèòðîâà, Å., Ïàíàéîòîâ, Â., Äðàãîâ, Ï., Àëåêñèåâ, Å. 1964.– Èçâ. Ãåîë. è-ò “Ñòð. Äèìèòðîâ”, 13; 223—260.Äèìèòðîâà, Å., Áåëìóñòàêîâà, Õ. 1986. – Ãåîõ., ìèíåðàë.è ïåòðîë., 20—21; 69—96.Åñêåíàçè, Ã., Õàðêîâñêà, À., Ñòåôàíîâà, Ë. 1984. – Ãåîõ.,ìèíåðàë. è ïåòðîë., 19; 33—42.Æåëÿçêîâà-Ïàíàéîòîâà, Ì., Êîë÷åâà, Ê., Áîÿäæèåâ, Ñ., Èâ-÷èíîâà, Ë., Âú÷åâ, Â., Ïåòðîâ, Ï. 1978 1. – Geol. Balcanica,8, 3; 9—24.Æåëÿçêîâà-Ïàíàéîòîâà, Ì., Èâ÷èíîâà, Ë., Êîë÷åâà, Ê.,Áîÿäæèåâ, Ñ., Âú÷åâ, Â., Ïåòðîâ, Ï. 1978 2. – Geol.Balcanica, 8, 4; 27—48.Çàêàðèàäçå, Ã. Ñ., Àäàìèÿ, Ø. À., Êîë÷åâà, Ê., Æåëÿçêîâà-Ïàíàéîòîâà, Ì. Ä., Äàíþøåâñêèé, Ë. Â., Ñîëîâüåâà, Í.Â., Êîëåñîâ, Ã. Ì., Ìèíèí, Ä. À. 1993. – Ïåòðîëîãèÿ, 1,1; 50—87.Èâàíîâ, Æ., Êîë÷åâà, Ê., Ìîñêîâñêè, Ñ. 1974. – Ãîä. Ñîô.óí-ò “Ñâ. Êë.Îõðèäñêè”, Ãåîë.-ãåîãð. ô-ò, 1, ãåîëîãèÿ,65; 245—277.Èâàíîâ, È., Òàøåâ, Í., Ïåòðîâ, Ï. 1985. – Ðóäîîáð. ïðîöåñèè ìèíåð. íàõîäèùà, 22; 16—29.Èâàíîâ, Ð., Ñòîÿíîâà, Ö. 1966. – Tð. ãåîë. Áúëãàðèÿ, ñåð.ãåîõ., ìèíåð. è ïåòð., 6; 83—102.Êàíóðêîâ, Ã., Ïåòðîâà, Ê., Êèíòèøåâà, Ð., Ñîêîëîâ, Í. 1986.– Ãîä. Êîì. Ãåîëîãèÿ, 26; 41—59.Êîâà÷åâ, Â. Â. 1979. – Ãîä. Âèñø ìèííî-ãåîë. è-ò, 25, 2;179—191.Êîæóõàðîâ, Ä. 1966. – Ñï. Áúëã. ãåîë. ä-âî, 27, 1; 51—62.Êîæóõàðîâà, Å. 1984. – Geologica Balñ., 14, 4; 9—36.Êîæóõàðîâà, Å. 1998. – Ãåîõ., ìèíåðàë. è ïåòðîë., 34;125—143.75
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