IOCG - mGals and nTs13 May 2022 16:30
Hi all
Here is an interesting and mercifully short article on IOCG deposits, for those up for a bit of weekend reading: https://www.tandfonline.com/doi/pdf/10.1071/ASEG2012ab278
A few points which seemed to me to be of interest:
- The article refers to the range of gravity anomaly values for the IOCG deposits discussed, suggesting that Olympic Dam has a particularly large gravity value at 17mGal. Our gravity value at the GRS is a whopping 30mGal. I wonder whether it’s too simplistic to hope that this is supportive of our deposit, if we have one, potentially being even larger than OD. I’m sure there are other possible explanations for our particularly high gravity reading but, since OD’s figure is at the top end of the range discussed in the article, it seems likely that high is good in this context.
- The article also refers to the range of magnetic values for the IOCG deposits discussed, mentioning OD as having a relatively low value at 1000 nano teslas, while other deposits have up to 7000. We have 2250 at the GRS, so again more than at OD.
- The article mentions that gravity readings are not much affected by the depth of the source whereas magnetic readings can ‘attenuate exponentially’ with depth. Since the GRS target is rather deep, I wonder whether our magnetic reading is artificially suppressed and may be higher “at source”.