Geochronology, petrogenesis and tectonic setting of the Eocene-Oligocene intrusive rocks in Chiclayo area, north of Peru

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P588.12; P581

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    In order to fully understand the tectono-magmatic evolution of the coastal batholiths of northern Peru since the Eocene, and to discuss the formation age, petrogenesis and tectonic environment of the intrusive rocks, typical samples were systematically collected from the coastal batholiths from west to east. The LA-ICP-MS zircon U-Pb chronology dating results show that the intrusive rock age is divided into two periods, 52~47 Ma and 36~28 Ma, which gradually change new from west to east. The rock geochemistry of the sample has the characteristics of calc-alkaline and high-potassium calc-alkaline, with a clear enrichment of large ionic lithophilic elements such as Rb, Ba, K and U, and a relative lack of high field strength elements such as Nb, Ta, P and Ti. The pattern of the chondrite-normalized REE distribution shows a right-leaning type of LREE enrichment with a clear negative Eu anomaly. The Sr/Y-Y diagram and Rb-(Y+Nb) diagram show the characteristics of island arc magmatic rocks. Both the Rb/Sr and Th/U ratios are close to those characteristics of crustal magma. The Nb/Ta ratio and Zr/Hf ratio are close to the average continental crust composition. The La/Ba-La/Nb diagram indicates the characteristics of the lithospheric mantle source region. The A/MF-C/MF diagram shows that most of the samples fall into the partial melting zone of the basic rock. Combined with the tectonic background of the subduction of the Nazca plate to the South American continental plate and the characteristics of the geochemical and chronological data of the samples, it is considered that the magma of the two intrusive rocks have homologous characteristics, and the magma source area may be derived from the partial melting of the basic lower crust and the contamination of the lithospheric mantle material. Under the low-angle slab subduction of the Nazca plate, the magmatic arc migrated eastward, and the time period of the crustal uplift and thickening was slightly later than the 30 Ma in the central and southern areas (after about 28 Ma).

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姚春彦,郭维民,刘君安,李汉武,王天刚,2024,秘鲁北部奇克拉约地区始新世-渐新世侵入岩时代、成因和构造环境[J].岩石矿物学杂志,43(1):1~20. YAO Chun-yan, GUO Wei-min, LIU Jun-an, LI Han-wu, WANG Tian-gang,2024,Geochronology, petrogenesis and tectonic setting of the Eocene-Oligocene intrusive rocks in Chiclayo area, north of Peru[J]. Acta Petrologica et Mineralogica,43(1):1~20.

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  • Received:April 14,2023
  • Revised:November 26,2023
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  • Online: January 18,2024
  • Published: January 25,2024