Karroo- Birds River, Western Minerals Supplementary Information
OCR PDF of supplemental information for Karroo- Bird's River Petrographic Suite
Western Minerals, inc
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KBR- Suite
Volcanic Breccia
This is a volcanic breccia from the farm Murrelfontein adjacent to the contact with the gabbro unit. It includes partially melted glass and tridymite, a high temperature polymorph of quartz, and has a brecciated appearance. The breccia has a allotriomorphic- granular texture and is holocrystalline. Coarse, anhedral, chaotic-looking dark black crystals (3-12mm) are surrounded by slightly lighter colored, smaller anhedral crystals (2 mm -6 mm). There are trace olivine phenocrysts (2 mm).
No date given.
Western Minerals, Inc.
KBR-19
Dolerite
This is dolerite from the "Dragon's Back" dyke, from the farm Romance. It is the youngest dolerite body in the area and contains biotite and hornblende. Emplacement of this dolerite took place at a much deeper crustal level than the gabbros. It has an aphanitic- porphyritic texture and is holocrystalline. The groundmass is light gray and subhedral. It contains slightly darker gray fine grained subhedral phenocrysts that comprise 30% of the dolerite. There is pinkish- brown blotchy weathering.
The thin sections are shown in plain polarized light and cross polarized light at a magnification of 400x and contains 60% plagioclase, 35% pyroxenes, and 5% opaques.
No date given.
Western Minerals, Inc.
KBR-18
Metasomatised Pyroclastics
The metasomatised pyroclastics are from the farm Thysfontein. They are baked and well indurated. Induration is the hardening of rocks by heat or baking as well as the hardening of sediments by cementation or compaction. The pyroclastics are metesomatised, chemically altered by hydrothermal fluids. It has coarse to medium grained, holocrystalline,and hypidiomorphic-granular texture. There are black subhedral crystals (1 mm- 4 mm). The surface is weathered to be white and yellow. There are 1 mm- 2 mm pock marks of red staining on the fresh surface.
No date given.
Western Minerals, Inc.
KBR-17
Adinole
Adinole was collected from the farm Murrelfontein and occurs above a conspicuous dolerite pegmatite. Adinole is a dense rock of mostly quartz and albite formed as the alteration product of contact metamorphism. It is potassium-rich and has hercynite, a mineral that can occur in high-grade metamorphosed iron rich argillaceous sediments. This adinole is a medium grained, holocrystalline, hypidiomorphic-granular texture.There are gray crystals ranging from < 1 mm- 3 mm. It has a dusty red and yellow weathered surface. It has a vein of a very dark aphanitic material.There is a radiating structure present in thin section.
No date given.
Western Minerals, Inc.
KBR-16
Hornfels
This hornfels was collected from a section of contact metamorphism immediately above the dolerite of the formation from the farm Murrelfontein. It has "spots" of quartz, most likely inverted from tridymite spherulites, in a matrix of devitrified glass with mullite and cordierite. It has an aphanitic- porphyritic texture and is holocrystalline. The ground mass is light gray and anhedral, medium-grained dodecahedral brownish gray phenocrysts make up 25% of the hornfel. Some small spots of bright red iron staining (~1 mm) occur. The phenocrysts are opaque in thin section.
Thin sections are shown in plain polarized light and cross polarized light at a magnification of 40x. The rock is 70% quartz and 30% opaques. The groundmass is quartz.
No date given.
Western Minerals, Inc.
KBR-15
Porphyroblastic Metasediments
The porphyroblastic metasediments/hybrid rocks were interpreted by Eales and his co-workers to be metamorphosed "Red Beds" Formation sediments but could be magmatic in origin. The samples illustrate the range in textures; see KBR 12 and KBR 13 to note this range. This sample is medium grained, holocrystalline, and has a hypidiomorphic-granular texture. It has dark gray crystals, ranging from < 1 mm- 3 mm. Dramatic labradorite-like striations cover about half of the rock. Groups of striations are roughly at right angles to one another. The rusty looking weathered surface is more vibrant on this rock (than the other samples).
The thin sections shown in plain polarized Light and cross polarized light at 40x magnification.
The rock is 60% plagioclase, 40% pyroxenes (mainly enstatite), and <1% opaques.
No date given.
Western Minerals, Inc.
KBR-14
Porphyroblastic Metasediments
The porphyroblastic metasediments/hybrid rocks were interpreted by Eales and his co-workers to be metamorphosed "Red Beds" Formation sediments but could be magmatic in origin. The samples illustrate the range in textures; see KBR 12 and KBR 14 to note this range. This sample has an aphanitic- porphyritic texture and is holocrystalline. There is a light gray anhedral ground mass and medium-grained phenocrysts (1 mm- 3 mm).There are fine, snaky veins of reddish material on the fresh surface. Minor euhedral phenocrysts of plagioclase with reaction rims (4 mm).
The thin sections shown in plain polarized light and cross polarized light at 40x magnification.
The rock is 40% plagioclase, 20% pyroxenes (Enstatite), and 20% opaques.
No date given.
Western Minerals, Inc.
KBR-13
Porphyroblastic Metasediments
The porphyroblastic metasediments/hybrid rocks were interpreted by Eales and his co-workers to be metamorphosed "Red Beds" Formation sediments but could be magmatic in origin. The samples illustrate the range in textures; see KBR 13 and KBR 14 to note this range. This sample has an aphanitic porphyritic texture. There are unfoliated coarse-grained metasediments (2 mm- 4 mm) and subhedral muscovite phenocrysts (2 mm - 3 mm) as well as red anhedral phenocrysts. There is a rusty-looking weathered surface. In thin section, radiating pyroxenes are clearly visible.
Thin sections are shown in plain polarized light and cross polarized light at 40x magnification.
The rock is comprised of 70% plagioclase, 22% pyroxene (mainly augite), and 8% opaques.
No date given.
Western Minerals, Inc.
KBR-12
Intersertal Ferrothoeleiite
The intersertal ferrotholeiite samples are highly fractionated and were most likely emplaced before the gabbro of the formation. They have textures associated with rapidly frozen or highly viscous melts. KBR-7 through KBR-10 are also intersertal ferrotholeiites. Intersertal is a texture marked by the occurrence of interstitial glass between laths of feldspar, usually in basalts. It has an aphanitic porphyritic texture and is holocrystalline. It has a consistent dark gray color and contains fine veins of quartz <1mm wide. There are medium grained subhedral plagioclase phenocrysts (2 mm- 5 mm). There is a calcic residue on a heavily oxidized weathered surface. There is a subophitic micro-texture. Radiating pyroxenes are clearly visible in plain polarized light.
Thin sections are shown in plain polarized light and cross polarized light at 40x magnification.
The rock is comprised of 65% plagioclase, 30% pyroxenes (mainly enstatite), and 5% opaques.
No date given.
Western Minerals, Inc.
KBR-11
Intersertal Ferrothoeleiite
The intersertal ferrotholeiite samples are highly fractionated and were most likely emplaced before the gabbro of the formation. They have textures associated with rapidly frozen or highly viscous melts. KBR-7 through KBR-9 and KBR 11 are also intersertal ferrotholeiites. Intersertal is a texture marked by the occurrence of interstitial glass between laths of feldspar, usually in basalts. It has an aphanitic- porphyritic texture and is holocrystalline. It has a consistent dark gray color with fine veins of quartz < 1mm wide. There are medium grained subhedral plagioclase phenocrysts (2 mm - 5 mm). There is a calcic residue on a heavily oxidized weathered surface. There is also a subophitic micro-texture. Poikolitic pyroxenes are visible in plain polarized light.
Thin sections are shown in plain and cross polarized light at 40x magnification.
The rock is comprised of 70% plagioclase, 30% pyroxenes (mainly augite), and <2% opaques.
No date given.
Western Minerals, Inc.
KBR-10
Intersertal Ferrothoeleiite
The intersertal ferrotholeiite samples are highly fractionated and were most likely emplaced before the gabbro of the formation. They have textures associated with rapidly frozen or highly viscous melts. KBR-7, KBR 8, KBR 10, and KBR 11 are also intersertal ferrotholeiites Intersertal is a texture marked by the occurrence of interstitial glass between laths of feldspar, usually in basalts. It has an aphanitic- porphyritic texture and is holocrystalline. It has a consistent dark gray color and fine veins of quartz <1mm wide. There are medium grained subhedral plagioclase phenocrysts (2 mm- 5 mm). There is a calcic residue on a heavily oxidized weathered surface. There is also a subophitic micro-texture. Radiating pyroxenes are clearly visible in plain polarized light.
Thin sections are shown in plain and cross polarized light at 40x magnification.
The rock is made up of 55% plagioclase, 30% pyroxenes (mainly augite), and 15% opaques.
No date given.
Western Minerals, Inc.
KBR-9
Intersertal Ferrothoeleiite
The intersertal ferrotholeiite samples are highly fractionated and were most likely emplaced before the gabbro of the formation. They have textures associated with rapidly frozen or highly viscous melts. KBR-7 and KBR-9 through KBR-11 are also intersertal ferrotholeiites. Intersertal is a texture marked by the occurrence of interstitial glass between laths of feldspar, usually in basalts. It has an aphanitic- porphyritic texture and holocrystalline. It has a consistent dark gray color with fine veins of quartz <1 mm wide. There are medium grained subhedral plagioclase phenocrysts (2 mm - 5 mm). There is a calcic residue on a heavily oxidized weathered surface. Radiating pyroxene crystals are clearly visible in plain polarized light.
Thin sections are shown in plain and cross polarized light at 40x magnification.
The rock is comprised of 55% plagioclase, 15% pyroxene, 12% biotite, 10% opaques, and 8% olivine.
No date given.
Western Minerals, Inc.
KBR-8
Intersertal Ferrothoeleiite
The intersertal ferrotholeiite samples are highly fractionated and were most likely emplaced before the gabbro of the formation. They have textures associated with rapidly frozen or highly viscous melts. KBR-8 through KBR-11 are also intersertal ferrotholeiites. Intersertal is a texture marked by the occurrence of interstitial glass between laths of feldspar, usually in basalts. Between the location this sample was collected and KBR-6 was collected, there is a thin gabbro pegmatite which was not collected. It has an aphanitic porphyritic texture and is holocrystalline. It has a consistent dark gray color with fine veins of quartz < 1mm wide. There are medium grained subhedral plagioclase phenocrysts ( 2mm - 5 mm). There is a calcic residue on heavily oxidized weathered surface. A subophitic micro-texture is also present. Spherulitic pyroxenes are clearly visible in cross polarized light.
Thin sections are shown in plain and cross polarized light at 40x magnification.
The rock is composed of 40% plagioclase, 40% pyroxene (mainly augite), 10% biotite, 5% olivine, and 5% opaques.
No date given.
Western Minerals, Inc.
KBR-7
Tholeiitic Gabbro
KBR-3 through KBR-6 are a second gabbro mass, distinguished from the first by a repetition of the differentiation cycle. Between the location this sample was collected and the location KBR-7 was collected there is a thin gabbro pegmatite that was uncollected. This sample is medium grained and holocrystalline with a hypidiomorphic-granular texture.There are gray and black crystals, both about ranging from <1mm- 3mm. There is a reddish, rusty looking weathered surface. This rock has an average specific gravity.
Thin sections shown in plain and cross polarized light at 40x magnification.
The rock is made up of 65% plagioclase, 35% pyroxene, (mainly augite), and 3% opaques.
No date given.
Western Minerals, Inc
KBR-6
Tholeiitic Gabbro
KBR-3 through KBR-6 are a second gabbro mass, distinguished from the first by a repetition of the differentiation cycle. The gabbro is medium grained and holocrystalline with a hypidiomorphic-granular texture. There are gray and black crystals, both ranging from <1mm- 3mm. There is a reddish, rusty looking weathered surface. This rock has an average specific gravity.
Thin sections shown in plain and cross polarized light at 40x magnification.The rock is made up of 80% plagioclase, 20% pyroxene (mainly augite), and ~2% opaques.
No date given.
Western Minerals, Inc
KBR-5
Tholeiitic Gabbro
KBR-3 through KBR-6 are a second gabbro mass, distinguished from the first by a repetition of the differentiation cycle. The gabbro is medium grained and holocrystalline with a hypidiomorphic-granular texture. There are gray and black crystals, both ranging from <1mm- 3mm. There is a red rusty looking weathered surface. This rock has an average specific gravity.
Thin sections shown in plain and cross polarized light at 40x magnification.
The rock is made up of 65% plagioclase, 25% pyroxene (mainly augite), and 10% opaques.
No date given.
Western Minerals, Inc
KBR-4
Tholeiitic Gabbro
KBR-3 through KBR-6 are a second gabbro mass, distinguished from the first by a repetition of the differentiation cycle. The gabbro is medium grained and holocrystalline with a hypidiomorphic-granular texture. There are gray and black crystals, both ranging from <1mm- 3mm.There is a red rusty looking weathered surface. The rock has an average specific gravity.
Thin sections are shown in plain and cross polarized light at 40x magnification.
The rock is made up of 65% plagioclase, 34% pyroxene (mainly augite), and <2% opaques.
No date given.
Western Minerals, Inc
KBR-3
Tholeiitic Gabbro
Samples KBR-1, KBR-2, KBR-2A are from a vertical mass of gabbro showing progressive differentiation inward.This sample is the second sample for KBR-2. This sample is medium grained and holocrystalline with a hypidiomorphic-granular texture. There are gray and black crystals, both ranging from <1mm- 3mm. There is a red rusty looking weathered surface. This rock has an average specific gravity.
No date given.
Western Minerals, Inc
KBR-2A
Tholeiitic Gabbro
Samples KBR-1, KBR-2, and KBR-2A are from a vertical mass of gabbro showing progressive differentiation inward. This sample is medium grained and holocrystalline with a hypidiomorphic-granular texture. There are gray and black crystals, both ranging from <1mm- 3mm. There is a red rusty looking weathered surface. This rock has an average specific gravity.
Thin sections are shown in plain and cross polarized light at 40x magnification.
The gabbro is composed of 70% plagioclase, 30% pyroxene (mainly augite), and <1% opaques.
No date given.
Western Minerals, Inc
KBR-2