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The effects of magmatic intrusions on temperature history, diagenesis and porosity development in sedimentary basins (COMPLETED 23.04.2020)

PhD-Candidate Magnhild Sydnes

Magnhild Sydnes
Photo:
Magnhild Sydnes, UiB

Articles

The influence of magmatic intrusions on diagenetic processes and stress accumulation

About the PhD-project

Magma that does not reach the surface but remains in the subsurface is called magmatic intrusions. At the time of the intrusion, the magma may have temperatures above 1000 ° C, while the environment it intrudes has significantly lower temperatures. In a sedimentary basin, such a heat supply will, among other things, accelerate the process of conversion of organic matter (Fig. 1). In my project, I will study the effect of intrusions on temperature history and maturation of hydrocarbons, analyze how sensitive the temperature history is to various factors in structurally complex basins with magmatic intrusions and the impact of intrusions on diagenesis and porosity development.

Magmatiske intrusjoner i basseng

Figure 1: Magmatic intrusions increase the conversion of organic matter into their environment. The figure shows the difference in maturity when a); one compares a basin without intrusions and a basin where there are 100 meter thick intrusions, and b); one compares a basin of 50 meter thick intrusions and a basin where there are 100 meter thick intrusions.

Photo:
Magnhild Sydnes, UiB

The thickness of the intrusions has a great influence on the temperature effect. Where several magmatic intrusions are relatively dense, the timing of their intrusion relative to each other may have an effect on the overall impact they have on temperature and thus also on the maturation of organic matter.

The structural evolution of sedimentary basins influences the effect of intrusions. The time difference between fault movement and when the magma entered, and the physical properties of the host rock, are crucial for the temperature effect.

Chemical compaction is also a temperature dependent process affected by magmatic intrusions. Results show that the porosity decreases in the surroundings of the intrusions as a consequence of the increase in temperature. However, the diagenesis process also changes the physical properties of the rocks, which can cause the rocks to respond differently to local stress conditions, thus contributing to increased fluid flow in some areas.