Interpretacja grawimetrycznej anomalii Tajno

Andrzej Grobelny





The interpretation has been made by a method worked out by D. C. Skeels. The pyroxenite intrusive body Tajno occurs in the granitoid mantle, where the average value of bulk density amounts to 2,70 G/cm3. The intrusive body is built up of a differentiated rock complex characterized by an average value of its bulk density equal to 3,14 G/cm3. Based on these assumptions the author has considered in his calculation a contrast of the density of rock equal to 0,44 G/cm3. As a result of the interpretation the following data have been obtained for the individual gravimetric sections:

Section A-B   D1        D2             W

left side          826   1424    2421

right side        689   1406    1350

Section C-D

left side          576   1280    1280

right side        600   1250    2125

Section E-F

left side          550   1222    1464

right side        588   1251    2252

Section G-H

left side          580    1261   1891

right side        588    1089    2722

Where: D1- depth down to the top of the disturbing body in metres; D2 – depth down to the bottom of the disturbing body in metres; W - width of the disturbing body in metres. The interpretation made according to Skeels method creates a possibility to determine the surface extent of the intrusion. This extent has been presented in Fig. 1. The results obtained from bore holes Tajno 1, Tajno 3, and Tajno 5 corroborate the interpreted boundary of the intrusion. The bore hole Tajno 6 pierced the altered pyroxenite which proves the existence of a peripheric zone of the intrusive body. The results obtained in bore hole Tajno 2 are contradictory to the interpretation performed, this, however, can be an apparent contradiction only, since the melanocratic syenites pierced in bore hole Tajno 2 represent the younger intrusive phase, which, in principle, uses the systems of fine fissures in the basement. It is not unlikely that the main zone of the fissure system runs, in the form of a narrow strip from the Tajno anomaly northwards.

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