Radon and carbon gas anomalies along the Watukosek Fault System and Lusi mud eruption, Indonesia

The relationship existing among the measured parameters suggests that the WFS acts as a preferential pathway for active rise of deep fluids. The presence of such advective processes is suggested by the relatively high rate of migration needed to obtain anomalies of short-lived 222Rn in the soil pores. Gas molecular and isotopic composition reveals that all sampled localities have a mixed hydrocarbon origin implying the presence of shallow microbial and deeper thermogenic hydrocarbons. CO2 isotopic values (δ13C-CO2 ranges between −9.48‰ and 4.12‰ V-PDB) indicate the presence of mantle derived CO2 and thermo-metamorphic CO2 suggesting that elevated temperatures have a key role in this active system. The samples collected from fractured and faulted zones reveal to have gas composition similar to that obtained from Lusi crater, indicating deep origin fluids.