Potential analytical interferences when measuring Tmax during temperature programmed pyrolysis of hydrothermally altered volcanoclastic sediment

Abstract

The temperature of maximum pyrolysis yield (known as Tmax) can be used to determine the level of thermal alteration in sedimentary organic matter; higher Tmax values represent higher thermal alteration. Tmax is commonly measured on petroleum source rocks or similar sediments with high organic carbon contents. It would be desirable to measure the Tmax of volcanic sediments because they can have complex patterns of thermal alteration. However, volcanic sediments often have low total organic carbon contents and consequently are susceptible to analytical interferences. Despite this, it can be shown that meaningful Tmax measurements can still be made in sediment with organic carbon contents as low as 0.2% and that interference caused by bitumen or ionizable salts can be mitigated by solvent extraction and rinsing with water. Thus, it is reasonable to use temperature programmed pyrolysis to assess levels of thermal alteration in even low total organic carbon volcanoclastic sediments.

Keywords

• Rock-Eval
• temperature programmed pyrolysis
• thermal maturity
• Tmax
• volcanic sediment