Dr. Nagy I. Zoltán szerk.: Fragmenta Mineralogica Et Palaentologica 3. 1972. (Budapest, 1972)

by investigations of the Al/Si distribution of feldspars which indicate a uniform cooling history of all dikes. The chief mineral constituents and their order of crystallization are also the same. All these indicate similar genetic cicumstances. Nevertheless ,if the dike rocks are considered from the standpoint of nomenclature, distinctions must be made. Mafic minerals make up about the one-third of the composition only In the Sárhegy dike, accordingly here is the highest content of PeO+MgO. On the basis of this fact and other characteristics (field occurrence ,recurrence of hornblende in two generations and its alteration to chlorite, occurrence of secondary titanite, high volatile and alkali content)the Sárhegy dike rock can be regarded as a lamprophyr, though it is not a typical one. The amount of quartz is relatively high and it contains less PeO+MgO than lamprophyres generally do, there is no C0£ in the composition, and finally the texture has a less pronounced porphyritic character. Considering tha't the hornblende-plagioclase assemblage is the dominant one in the Sárhegy dike, the rock ought to be named spessartite instead of kesantite. Obviously the other dike rocks can not be regarded as lamprophyres.Since the features characteristic of the Sárhegy dike are more or less characteristic of these rocks too, they can be considered as dike rocks of "lamprophyric character". In the rock of the Székesfehérvár Quarry the biotite-orthoclase assemblage is also important with a higher amount of quartz.The Csala Porest dike shows intermediate features. Thus the composition seems to have shifted from a lamprophyric starting state towards a more granitic one. Lamprophyres were once thought to have developed through differentiation processes of granitic-dioritIc magmas, and they were supposed to have associated with certain classes of plutonic rock (minette and vogesite with granite, and kersantite as well as spessartite with diorite). Now these suppositions are generally denied and lamprophyres are thought to have risen from an independent source along fractures formed in response to previous emplacement of granitic or dioritic plutons.Some potassic