I-1 Intrusive
I-1 Intrusive
A piece of lamprophyre dyke from Gary's Corner that fragments (xenoliths) of what is likely the I-1 intrusive body. These fragments are aligned parallel to the edges of the lamprophyre dyke
What Do the I-1 Rocks Look Like?
Based on the interpretation that the fragments that are found in the lamprophyrye dyke is the I-1 intrusive, then the compostion fo the I-1 Intrusive is a calc-alkaline porphyritic diorite. If these are in fact pieces of the I-1 Intrusive, then the lamprophyre dykes are younger than the epithermal mineralization. This is not an unusual association, and it means that there was a much larger intrusive body under the epithermal deposit, and this has been cut by a younger lamprophyre dyke.
Unfortunately with the estimated depth to the top of the intrusive body, it can only be hit with an extremely deep drill hole. Modelling shows that the I-1 intrusive comes very close to the Silver Cup Anticline, and in this area there is a string of em anomalies that originate and project into the Thor epithermal deposit. It is very likely that is the deep source of the epithermal deposit itself.
Unfortunately with the estimated depth to the top of the intrusive body, it can only be hit with an extremely deep drill hole. Modelling shows that the I-1 intrusive comes very close to the Silver Cup Anticline, and in this area there is a string of em anomalies that originate and project into the Thor epithermal deposit. It is very likely that is the deep source of the epithermal deposit itself.
A piece of lamprophyre dyke with inclusions of what are most likley fragments (or xenoliths) of I-1 Intrusive rock. These xenoliths are porphyritic and characterized by albite (scale is in cm)
View of the Thor epithermal deposit (light brown) with conductive Tusks (yellow). I-1 Intrusive feature is shown in dark green, and lamprophyre dyke is shown in light green. Brown feature around lamprophyre dyke is the lamprophyre alteration
What is the I-1 Intrusive?
Mapping the I-1 Intrusive
The I-1 Intrusive is not exposed at surface anywhere at Thor. The existence of this intrusive is inferred from geophysical data and also from drill core.
Within the lamprophyre dykes at Thor, there are areas that contain large 'fragments' of porphyritic intrusive rock. This is graphically shown in the sample above, and the fragments are aligned along within the Mg-rich matrix of the lamprophyre dyke.
These fragments are porphyritic in places and contain numerous quartz eyes and feldspar pheonocrysts (albite). These are believed to pieces of the underlying I-1 intrusive that have been transported up in the lamprophyre dyke.
Age relationships (those shown in the rock above) show that the I-1 intrusive is the oldest intrusive body at Thor, and a lamprophyre dyke originated from this intrusive body and crosscut the I-1 intrusive. In intrusive-related epithermal deposits, it is not unusual to have two or more ages of intrusive, all related, and some mineralized and others mineralized.
Within the lamprophyre dykes at Thor, there are areas that contain large 'fragments' of porphyritic intrusive rock. This is graphically shown in the sample above, and the fragments are aligned along within the Mg-rich matrix of the lamprophyre dyke.
These fragments are porphyritic in places and contain numerous quartz eyes and feldspar pheonocrysts (albite). These are believed to pieces of the underlying I-1 intrusive that have been transported up in the lamprophyre dyke.
Age relationships (those shown in the rock above) show that the I-1 intrusive is the oldest intrusive body at Thor, and a lamprophyre dyke originated from this intrusive body and crosscut the I-1 intrusive. In intrusive-related epithermal deposits, it is not unusual to have two or more ages of intrusive, all related, and some mineralized and others mineralized.
The location of the I-1 Intrusive body is mapped using MT resistivity. The depth of the intrusive body means that it cannot be mapped with magnetic surveys. MT is able to map a resistive, circular body that extends from a depth of about 500 mASL to an unknown depth.
Owing to its importance, the I-1 feature will probably be drilled in the future from the main access road where it comes the closest to surface.
The roots of the Thor epithermal mapped using electromagnetic surveys extend onto the northeast corner of the I-1 intrusive. where it comes into contact with the Silver Cup Anticline, and it is entrely possible that the source of the Thor deposit is related to this area.
Owing to its importance, the I-1 feature will probably be drilled in the future from the main access road where it comes the closest to surface.
The roots of the Thor epithermal mapped using electromagnetic surveys extend onto the northeast corner of the I-1 intrusive. where it comes into contact with the Silver Cup Anticline, and it is entrely possible that the source of the Thor deposit is related to this area.