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A. Stout subhedral crystal of apatite in unaltered phanerite. The field of view is
about 0.5 x 0.8 mm. Plane-polar light. DDH 351-313.2.
B. Stout subhedral to euhedral crystal of apatite in porphyry that has undergone
weak potassic alteration. The field of view is about 0.4 x 0.6 mm. Plane-polar
light. DDH 303-350.55.
C. Stout subhedral crystal of apatite in phanerite that has undergone propylitic
alteration. Tiny fluid inclusions are present in the crystal. These inclusions
contain bubbles of gas and at least one daughter mineral phase. The field of view
is about 0.8 x 1.2 mm. Plane-polar light. JDD-94-12.
D. Rounded crystal of zircon (center) in a pseudomorph of hydrothermal biotite and
quartz that has replaced a magmatic ferromagnesian mineral (probably pyroxene).
The zircon was an inclusion within the original magmatic mineral. The field of
view is about 0.2 x 0.3 mm. Plane-polar light. DDH 345-468.
E. Anhedral crystal of magnetite in a phanerite. This crystal is magmatic in origin.
A crystal of sphene is also shown (upper left). The field of view is about 0.7 x 1.0
mm. Plane-polar light. DDH 356-166.5.
F. Common magmatic accessory mineral assemblage in unaltered rocks of the Ok Tedi Intrusive Complex: pyroxene (pale green, lower left center), hornblende (moderate olive green, adjacent to pyroxene), magnetite (black), sphene (top center, adjacent to magnetite). A crystal of apatite (just out of field of view, but shown in Fig. 39A) rounds out the magmatic accessory mineral suite. The field of view is about 0.5 x 0.8 mm. Plane-polar light. DDH 351-313.2.
G. Several phenocrysts of magnetite are shown in this photomicrograph. Two of
these abut against a phenocryst of pyroxene. The lower one of these is euhedral
in shape; all other magnetite phenocrysts in the photo are subhedral or anhedral.
The mineral assemblage is magmatic. The field of view is about 1.3 x 2 mm.
Reflected light. DDH 458-151.8.
H. Typical distribution of magmatic magnetite in a sample of phanerite. Two size populations can be seen: (1) larger crystals many of which abut against crystals of pyroxene, and (2) small crystals that are scattered uniformly throughout the thin-section. The field of view is about 4.0 x 6.4 mm. Plane-polar light. DDH 74-66
