Abstract
Early Jurassic arc-related igneous rocks host porphyry copper prospects and gold-bearing quartz vein deposits in southern Peru. Ten new zircon U-Pb ages for wall rocks of gold-bearing quartz veins, Jurassic rocks and copper-mineralized porphyry bodies in Zafranal porphyry copper, together with published ages for Jurassic rocks, reveal a continuous magmatic evolution of the early Jurassic arc. The Jurassic rocks and gold-bearing quartz vein systems in the western flank of the Western Cordillera are hosted by Paleo- and Meso-proterozoic orthogneisses of the Arequipa Massif (1.75-1.44 Ga) that underwent Grenville-age metamorphism ~1 Ga. The early mafic magmatism is recorded between 199.6-193.2 Ma, and was followed by dominantly felsic magmatism from 184.1-174.9 Ma. Both magmatic events have formed the thinnest intrusive belt (
Highlights
Considerable volumes of magma in the Peruvian convergent margin magmatic-arc, that formed the Coastal Batholith, were generated during a protracted time span (Jenks and Harris, 1953; Cobbing and Pitcher, 1972; Cobbing et al, 1977)
The last magmatic event of the early Jurassic (181.0-174.9 Ma) is represented by several phases of porphyries associated with copper mineralization in the Zafranal porphyry copper deposit
This study aims to determine the early Jurassic arc extent to the northwest of Arequipa and crystallization age of porphyry bodies related to copper mineralization in Zafranal porphyry copper deposit by means of zircon U-Pb ages with sensitive high-resolution ion microprobe (SHRIMP) and laser ablation inductively-coupled plasma spectrometry (LA-ICP-MS) determinations
Summary
Considerable volumes of magma in the Peruvian convergent margin magmatic-arc, that formed the Coastal Batholith, were generated during a protracted time span (Jenks and Harris, 1953; Cobbing and Pitcher, 1972; Cobbing et al, 1977). According to the geochronological data the Coastal Batholith was considered to have been emplaced in late Cretaceous (Cobbing and Pitcher, 1972; Stewart et al, 1974; Cobbing et al, 1977; Weibel et al, 1978; Cordani et al, 1985; Beckinsale et al, 1985; Mukasa, 1986; Caldas, 1993; Schildgen et al, 2009; Carlotto et al, 2009a), but afterwards divided into two groups one early Jurassic and other Upper Cretaceous (Demouy et al, 2012; Boeckhout, 2012). This paper describes the regional geological setting of Jurassic intrusive rocks (Coastal Batholith-Arequipa Segment), with particular emphasis on the porphyritic bodies that host the copper mineralization in Zafranal, based on more than four years of fieldwork by the authors during a study of the Coastal Batholith program that included 1:25,000-scale regional mapping
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