Regional burial heating vs. local magmatic heat influence of the Rostånga area, Scania, southern Sweden
Title:
Regional burial heating vs. local magmatic heat influence of the Rostånga area, Scania, southern Sweden
Author:
Olsson, Ingela
Appeared in:
GFF
Paging:
Volume 121 (1999) nr. 3 pages 209-214
Year:
1999-09-01
Contents:
Illite crystallinity and vitrinite-like reflectance were studied within the Rostånga area to evaluate the degree of burial-related heat versus magmatic influence from the Permo-Carboniferous dolerite intrusions. At Rostånga three non-contact metamorphosed samples gave low diagenetic illite crystallinities with Kubler index values of 0.64-0.78 Δ°2θ. These results are in contrast to statements in the literature of high organic maturity (mean random reflectance, Ro 2-2.7%) within the area, and suggest that the short-lived magmatic heating, also at localities outside immediate dolerite contact zones, improved the organic maturity more than it did the illite crystallinity. The Kubler index and the reflectance values from the contact-metamorphosed Alum Shale at Åkarpsmolla are clearly affected by the magmatic heating caused by the dolerite intrusion. The crystallinity as well as the vitrinite-like Ro values show significantly higher maturity than indicated by the regional reference samples. All the Åkarpsmolla Ro values indicate that the rocks are overmature (3.9-5.8%) with respect to any petroleum generation, and fall within the anchimetamorphic to epimetamorphic zone, whereas the Kubler index values (0.42-0.73 Δ°2θ), due to the sluggish reaction rate of the clay mineral reactions, lag behind throughout the whole section and range within the diagenetic zone.
Journal description