Abstracts
Abstract
Primary flow features (schlleren banding, negacryat-xenollth alignment end blotlte foliation) within the eastern portion of the South Mountain Bathollth (SMB) reflect the geometry of intrusions and divides the study area into two distinct domains. In the eastern half the primary flow features display roughly concentric to random regional patterns related to differential flowage near contacts. Northeast-trending linear patterns characterize the western half and may in part reflect regional stress.
Stereonet evaluation of prominent joints, dykes and veins Indicate four primary-regional joint sets (trends), all of which are steeply dipping. The dominant joints, trends 2 (063 ) and 4 (145 ) form a roughly orthogonal pair parallel and perpendicular, respectively, to the regional fold axes. Trends 3 (130 ) and 5 (164 ) form a conjugate set around trend 4. Quartz vein orientations coincide with trend 4 end maxima of dykes correspond to trends 3, 4 and 5. Trends 2 to 5 are Interpreted as resulting from horizontal compression parallel to trend 4 during a period of uplift. Trend 1 (042 ) is associated with a major fault zone which has locally been superimposed on the pattern of primary-regional joints. Primary-regional joints have to some degree influenced the intrusion of the later phases of the SMB.
Mineralization within the SMB Is strongly controlled by the regional fracture patterns. Oraniuo mineralization generally occurs within altered trend 2 joints uhereas polymetallic veln-grelsen mineralization is generally associated with trend 4 joints.
RESUME
Lea caracteristiquea de flux prlmaires (rubatmement schlleren. allgnement des megscristes et xenolites, foliation de la biotlte) dans la portion orientale du Batholite de South Mountain (BSM) refletent la geometrie des intrusions et dlvlsent la region etudlee en deux domaines dlstlncts. Dans la dende orientale, les traits de flux prlmaires se foment en patrons reglonaux, approximatlvement concentriques a aleatoirea, relies au fluage differentiel pres des contacts. Des patrons llnealxes a tendance HE caracterlsent la demie occidentale et pourraient representer, en partie, une contralnte regionale.
line evaluation sur stereonet des dlaclases. dykes et veines evldents revele quatre families (tendances) de diaclases prlmaires regionales ayant toutes un pendage eleve. Domlnantes. les families dlrectlonnelles de fractures 2 (063 ) et 4 (145 ) foment une palre plus ou moins orthogonale, respectivement parallele et perpendiculaire aux axes de plis reglonaux. Les tendances 3 (130 ) et 5 (164 ) foment une famille conjuguee autour de la tendance 4. L'orientation des veines de quartz coincide avec la tendance 4. Le nombre maximum de dykes correspond aux families dlrectlonnelles 3. 4 et 5. On lors d'une periode line evaluation sur stereonet des dlaclases. dykes et veines evldents revele quatre families (tendances) de diaclases prlmaires regionales ayant toutes un pendage eleve. Domlnantes. les families dlrectlonnelles de fractures 2 (063 ) et 4 (145 ) foment une palre plus ou moins orthogonale, respectivement parallele et perpendiculaire aux axes de plis reglonaux. Les tendances 3 (130 ) et 5 (164 ) foment une famille conjuguee autour de la tendance 4. L'orientation des au patron des fractures prlmaires regionales. phases tardives du BSM.
Les patrons de fractures reglonaux ont fortement control* la mineralisation a l'interieur du BSM. La mineralisation en uranium occupe generalement des families dlrectlonnelles 2 alterees. Par contre, les mineralisations de type greisen ou filon polymetallique sont generalement associees aux diaclases de tendance 4.
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