Advective versus Conductive Heat Transfer During Development of the Lublin Basin (SE Poland) – Constraints from Maturity Modelling And Fluid Inclusion Analysis

Pawel POPRAWA¹ and Michal M. ZYWIECKI^2,3
1Polish Geological Institute, Warsaw, Poland; [email protected]
²Faculty of Geology, Warsaw University, Warsaw, Poland; [email protected]
³OG Petroleum Consulting, Warsaw, Poland

The Lublin Basin (LB) is a relatively small Neoproterozoic-Phanerozoic basin located in the SE Poland. It is characterized by a complex and laterally changeable thermal history, exemplified by development of individual zones of the basin with specific structure of thermal maturity and palaeotemperatures. The recently observed thermal maturity of the LB was achieved mainly during the Late Carboniferous and/or Mesozoic burial. The reconstructed Carboniferous heat flow is laterally changeable and not entirely representative due to significant role of advective heat transfer. Impact of advection on thermal maturity leads also to significant overestimation of apparent thickness of the eroded section, calculated from individual maturity profiles. In the eastern and north-eastern part of the LB thermal maturity of the lower part of the section developed during the late Devonian burial, coeval with relatively high heat flow. A hot palaeo-thermal regime at this stage might be attributed to transtensional tectonic event. In the north-western part of the studied area the measured thermal maturity locally might be attributed to the Early-Middle Jurassic activity of relatively hot, ascending fluids, migrating due to extensionally or transtensionally enhanced permeability of basement faults and fractures. There are several types of fluids identified, which affected in a very complex way palaeo-thermal regime of the LB and thermal maturity of its sedimentary fill. During the Middle Devonian to Late Carboniferous hot fluids released from chemical diagenesis of sediments were migrating though carrier beds upwards of structural surfaces from deeper buried zones, modifying the basin’s geotherm. The late Devonian significant burial of the central part of the LB, i.e. the Lublin Trough, led to mechanical compaction of the Devonian argillaceous sediments are subsequent release of compaction waters, often trapped in overpressure zones. Another, specific type of hot fluids appeared in Carboniferous time, energetically and chemically fed by igneous intrusions, casing positive temperature and thermal maturity anomalies along carrier bed. During the Carboniferous time the Late Devonian overpressure zone were unsealed by transtensional tectonics and dewatered, leading to upwards migration of the released, relatively hot fluids. This was roughly coeval with rapid burial phase, casing mechanical compaction of Carboniferous siliciclatics, and to lesser degree further compaction of the Devonian sediments. The released waters were trapped in the new overpressure zones, developed in the Carboniferous strata, either migrating laterally and upwards provoked partial homogenisation of thermal maturity in the individual section and development of relatively low thermal maturity gradients with relatively high maturity values. The later might be responsible, at least partly, for suspiciously high apparent thickness of the eroded section, calculated from maturity modelling. At the late-most Carboniferous to Early Permian the LB suffered transpressional deformation, uplift and erosion. As a result overpressured zones in the Carboniferous strata, and to the lesser degree in the Devonian one, were unsealed and dewatered. As a consequence a new phase of upward migration of relatively hot waters caused further homogenization of the thermal maturity of the LB sedimentary fill.

AAPG Search and Discover Article #90066©2007 AAPG Hedberg Conference, The Hague, The Netherlands