Overview of Results from the Greenstone ... - Geology Ontario

Chart A. Magnetic and Gravity Three-Dimensional (3D) Modelling Images
Figure 31. View (looking west from somewhat below the horizon) of 3D inversion of the magnetic and
positive gravity data for the Currie Township area. Amplitude-enhanced magnetic data are set above the surface.
The magnetic data in lower Blake River assemblage mafic volcanic rocks to the south show 2 limbs of a syncline
within a south-dipping gravity high also marking these volcanic rocks. The northern two-thirds of the area
(in Tisdale assemblage mafic volcanic rocks) shows a bimodal high low and high-gravity response and low
magnetic response. This image suggests a vertical to steep north dip on the northern higher density mafic
volcanic rocks.
Figure 34. North-south slice through the 3D magnetic (red) and negative gravity (blue) and positive gravity
(green) image of the Clifford stock and surrounding area. The view looks east with the surface geology just
visible at the top of the image. With reference to Figure 33, the slice cuts the east side of the magnetic anomaly
and does not intersect the hole in the doughnut that marks the core of the intrusion. The depression in the blue
gravity surface implies a gravity high, not fully developed by the isosurfaces presented here, which is occupied
by the magnetic high. As noted in Figure 33, the gravity low identifies the felsic volcanic rocks surrounding the
stock. Note, the magnetic body marking the edge of the stock, plunges south, apparently across the density low
of the felsic volcanic rocks.
Accompanies OFR 6154
Figure 32. Overhead view of the combined magnetic and gravity shells in parts of Tisdale and Deloro townships;
see text for a more detailed explanation.
Figure 33. Three-dimensional overhead view of the Clifford stock and surrounding area (4 townships of
Clifford, Ben Nevis, Arnold and Katrine). The positive gravity surface is light green, the negative gravity
surface is light blue and the magnetic surface is red. Overlying is a transparent image of the geology
( =BJAH Ayer et al. 2005). The Clifford stock (in a faded red) is surrounded by a doughnut-shaped magnetic
high (the magnetic margins of the stock), which is then surrounded by a doughnut-shaped gravity low
(reflecting surrounding felsic volcanic rocks), followed by a gravity high (from mafic to intermediate
volcanic rocks). Aseparate 3D section (Figure 34) shows the magnetic aureole plunges to the southeast.