Origin of the Oils hosted in intruded Igneous Rocks at the Vaca Muerta Formation, Cajón de los Caballos Oil Field, Mendoza Province, Neuquén Basin, Argentina. A set of oil samples produced from intrusive rocks emplaced in Vaca Muerta shales at the Cajón de los Caballos (CC) oil field, located south of the Mendoza Province in the northern Neuquén Basin, were submitted to a geochemical typing in order to elucidate source facies, oil-oil correlation, degree of preservation and level of thermal maturity. The methods applied include bulk characterization (API gravity, sulfur %, chemical group percentages, carbon isotopes of saturate/aromatic hydrocarbon fractions and whole oil), gas chromatography (GC) and gas chromatography – mass spectrometry (GCMS) for biomarker fingerprinting. The CC oil field is located a few kilometers to the east of the outstanding accumulations of the Valle del Río Grande area, where one of the most important reservoir systems is developed in igneous rocks that intruded the Vaca Muerta and Agrio formations (Mendoza Gr.). These oils bear geochemical signatures that link their origin to organic-rich intervals containing type II marine kerogen, present in both units that have largely sourced most of the oils of the Western-Central districts of the Neuquén Basin. Geochemical results on fluid samples recovered from intrusive bodies along with other samples produced from conventional reservoirs (Neuquén Gr. and Pre-Cuyo) show that the produced oils at CC oil field are heavy (API range: 11.9º-17.6º), highly viscous at room temperature, sulfur-rich (range: 1.9-2.9%), and have poor contents in saturated hydrocarbons and enhanced proportions of non-hydrocarbon compounds. These compositional properties are in line with alteration patterns due to biodegradation and with low to moderate thermal maturity, as shown by GC and biomarker distributions. More interestingly, the study documents that the fluids were sourced from non-marine rock intervals that can be ascribed to lacustrine shales typically present in organic-rich intervals of the Pre-Cuyo in the area. The analyses performed detect no evidence of contribution of marine source rock intervals like those present in the Mendoza Gr., that have fed the intrusive-Vaca Muerta reservoirs in the neighbor Valle del Río Grande fields.