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" Strike-slip faulting, breccia formation and porphyry Cu-Au mineralization in the Gunung Bijih (Ertsberg) Mining District, Irian Jaya, Indonesia "
B. Sapiie
M. P. Cloos
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Latin Dissertation
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English
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| Record Number
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1113384
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| Doc. No
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TLpq304457260
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| Main Entry
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B. Sapiie
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M. P. Cloos
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| Title & Author
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Strike-slip faulting, breccia formation and porphyry Cu-Au mineralization in the Gunung Bijih (Ertsberg) Mining District, Irian Jaya, Indonesia\ B. SapiieM. P. Cloos
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| College
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The University of Texas at Austin
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| Date
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1998
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| student score
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1998
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| Degree
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Ph.D.
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| Page No
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304
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| Abstract
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Most of the Cenozoic tectonic evolution in New Guinea is a result of obliquely convergent motion that led to an arc-continent collision between the Australian and Pacific Plates. The results of detailed structural mapping at the Gunung Bijih (Ertsberg) Mining District (GBMD) along a 15-km traverse of the Heavy Equipment Access Trail (HEAT) and the Grasberg mine access road have provided new information concerning the late Cenozoic structural evolution of the Central Range of Irian Jaya. Two distinct stages of deformation are recognized. The first stage, between 12 and 4 Ma, was the results of tens of kilometer of contractional deformation and generated km-scale NW-trending (usd\piusd-fold axis = 300 folds and minor reverse or thrust faulting. The second stage, a few kilometers of strike-slip offset, occurred between 4 and 2 Ma. Five major left-lateral strike-slip fault zones trending usd{\sim}299\sp\circusd were discovered in the GBMD. These fault zones bound structural domains of numerous minor faults that form networks of R and R Riedel shears. The Grasberg Igneous Complex (GIC), the host of a super-giant Cu-Au orebody, was emplaced into the center of the Yellow Valley Syncline at a 1 km wide left step connecting two of the major fault zones. Kinematic analysis of faulting within the GIC reveals three distinct strike-slip domains. Veining and ore mineralization are concentrated in a domain of overlapping R, R and D Riedel shears in the center of the GIC. Five end-member types of breccia are identified and their primary formative processes are interpreted. Type 1 breccia is related to the emplacement of the Dalam units of the GIC. Type 2 breccia is related to the explosive expansion of heated meteoric waters. Type 3 breccia is generated where high-temperature, acidic supercritical magmatic fluid enters into the contact zone of the GIC. Type 4 breccia is a product of dissolution of carbonate strata by cool, dilutely acidic, probably meteoric waters. Type 5 breccia is a product of tectonic fracturing and is common along the major, usd{\sim}299\sp\circusd-trending, left-lateral strike-slip faults.
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Breccia formation
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Copper-gold
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Earth sciences
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Faulting
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Indonesia
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Mineralization
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