학술논문
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 / Geochronology,petrogenesis and tectonic setting of the Eocene-Oligocene intrusive rocks in Chiclayo area,north of Peru
Document Type
Academic Journal
Author
Source
岩石矿物学杂志 / Acta Petrologica et Mineralogica. 43(1):1-20
Subject
Language
Chinese
ISSN
1000-6524
Abstract
为充分认识秘鲁北部海岸岩基带始新世以来的构造岩浆演化特征,探讨侵入岩形成时代、岩石成因及其构造环境,在海岸岩基带自西向东系统采集侵入岩样品.锆石U-Pb年代学数据显示侵入岩时代分两期,分别为52～47 Ma和36～28 Ma,具有自西向东逐渐变新的特征.样品岩石地球化学具有钙碱性-高钾钙碱性特征,明显富集Rb、Ba、K、U等大离子亲石元素,相对亏损Nb、Ta、P和Ti高场强元素;球粒陨石标准化稀土元素配分模式均表现为轻稀土元素富集的右倾型,具有弱的Eu负异常.Sr/Y-Y图解和Rb-(Y+Nb)图解显示岛弧岩浆岩的组成;Rb/Sr值和Th/U值接近壳源岩浆组成;Nb/Ta值和Zr/Hf值均接近平均陆壳组成;La/Ba-La/Nb图解指示具有岩石圈地幔源区的特征;A/MF-C/MF图解中多数样品落入基性岩的部分熔融区域.结合Nazca板块向南美大陆板块俯冲的构造背景及样品地球化学和年代学数据特征,认为两期侵入岩的岩浆具有同源特征,岩浆源区可能源于基性下地壳的部分熔融,并有岩石圈地幔物质混染;秘鲁北部在Nazca板块低角度平板俯冲作用下,岩浆弧向东迁移,同时地壳隆升和增厚时限较中南部地区的30 Ma时限稍晚(大约在28 Ma之后).
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).
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).