Geophysics

Anyone familiar with IOCG geophysics. My understanding is that an IOCG deposit has a prominent gravity anomaly. The image below is the CHK local gravity anomaly overlayed on top of the SARIG website data, sowing TMI and Gravity contours, I have also had a guess at the CHK hole locations. As can faintly be seen at oak dam west, there is a large gravity anomaly, however, within the vicinity of hole 4, which was partly mineralised, there is no gravity anomaly within the SARIG data or the local CHK data, which would indicate that no IOCG deposit exists in this area. Would this be a fair assumption? A gravity anomaly could exist where the local CHK gravity data is missing, does anyone know why there is no data below hole 4?