Sloan Pipe
The Sloan Pipe is one of 19 kimberlite pipes that cluster close to the Colorado-Wyoming boundary (McCallum et al., 1975, Fig. 1). Carbonatite xenoliths are found in several of the pipes but are particularly abundant in the Sloan Pipe.
The Sloan Pipe is one of 19 kimberlite pipes that cluster close to the Colorado-Wyoming boundary (McCallum et al., 1975, Fig. 1). Carbonatite xenoliths are found in several of the pipes but are particularly abundant in the Sloan Pipe.
The Central parts of the La Sal Mountains comprise three separate groups of clustering laccoliths. South Mountain consists predominantly of porphyritic diorites which contain a little aegirine-augite.
The pear-shaped Iron Hill complex covers some 31 km2 and is emplaced in Precambrian metamorphic and igneous rocks, principally granites in the vicinity of the complex, which are fenitized. Drilling seems to indicate that the complex tapers downwards (Temple and Grogan, 1965, p.684).
Within the La Plata Mountains of southwest Colorado are a number of syenitic stocks (see Eckel, 1949, Plate 2), only one of which, the Allard stock, has been described in any detail (Werle et al., 1984).
In the central part of the South Park basin in central Colorado lamprophyric intrusions outcrop as a dyke and a sill-like body about 1.6 km long. Eleven other intrusions of similar type and up to 16 m thick were encountered in a nearby oil well.
The Cripple Creek district lies in a dome-like flexure at the southwestern end of the Front Range and consists mainly of Precambrian granite, gneiss and schist, but in an area immediately east of the town of Cripple Creek and capping surrounding hills are sediments and volcanics of Tertiary age.
The Mount Rosa granite lies at the southern end of the composite Pikes Peak batholith. The batholith is composed principally of biotite and hornblende granites but quartz syenites and fayalite granites also occur (Barker et al., 1975).
An alkaline province in the northern Wet Mountains of Colorado includes three central complexes together with extensive swarms of carbonatitic and alkaline dykes and thorite veins (Armbrustmacher, 1984a). The central complexes of McClure Mountain-Iron Mountain (No. 89), Gem Park (No.
Within an area of 1000x300 m about 10 silico-carbonatite dykes up to 10 m thick, trending north-northwest-south-southeast, cut the Precambrian Pikes Peak granite. The largest dyke has a hanging wall of red, hematite-rich potassic fenite.
Two breccia pipes lie 1.2 km north of Pinon Peak, northwest of Iron Mountain (No. 89). The more northerly Wood Knob pipe is only 16 m in diameter, the southerly Gar Knob pipe about 80x20 m.