Rola magm zasadowych w ewolucji intruzji granitoidowych (studium porównawcze wybranych masywów hercyńskich).
Abstract
Role of basic magmas in the granitoid evolution (a comparative study of some hercynian massifs)
Abstract
Field, petrographical and chemical data give evidence for the existence of two types of magma that contributed to the formation of the studied granitoid massifs of Strzelin and Kłodzko - Złoty Stok (Lower Silesia, Poland) and western part of the Central System Batholith (Spain, Portugal). Two types of rocks were distinguished among granites: S-type anatectic two-mica granites with cordierite and metamorphic xenoliths, and I-type biotite (ą hornblende) granitoids with rare xenoliths and abundant magmatic mafic enclaves (MME). The shallow level intrusions of gabbro-dioritic rocks show clear evidence of magma mingling, mixing, and certain degrees of complex hybridization indicating that the granitoids cannot be led out from one type of magma. The mineral and chemical composition and shape of abundant MME, in parts showing features of orbicular development, suggest several pulses of a more mafic magma into felsic one, and wide thermal difference between the two. The biggest concentration of such enclaves occurs in granodiorites and tonalites, and their origin is closely connected with processes of interaction of acid and basic magmas achieved by various mechanisms. The coexistence of acid and basic rocks seems to be result of interaction of mantle and crustal magmas in such different tectonic regimes like continent-continent collision setting and the active margins of the continental plates above subduction zones. Typical examples of the both „hercynotype” and „andinotype” plutonism are described with clear evidence of important role played by basic magmas in the granitoid genesis