江西中部新丰街花岗质岩体LA-ICP-MS锆石U-Pb年代学、元素和Sr-Nd-Hf同位素地球化学特征及岩石成因

J4 ›› 2016, Vol. 22 ›› Issue (3): 431-.

江西中部新丰街花岗质岩体LA-ICP-MS锆石U-Pb年代学、元素和Sr-Nd-Hf同位素地球化学特征及岩石成因

朱书奇，姜耀辉*，王国昌，倪春雨，青龙

出版日期:2016-09-20 发布日期:2016-10-09

LA-ICP-MS Zircon U-Pb Geochronology, Elemental and Sr-Nd-Hf Isotopic Geochemistry of the Xinfengjie Granitic Intrusion in Central Jiangxi Province, SE China, and Its Petrogenesis

ZHU Shuqi, JIANG Yaohui*, WANG Guochang, NI Chunyu, QING Long

Online:2016-09-20 Published:2016-10-09

摘要/Abstract

摘要：

对江西中部新丰街花岗质岩体开展了岩相学、LA-ICP-MS锆石U-Pb年代学以及元素和Sr-Nd-Hf同位素地球化学研
究，并探讨了岩石成因及其构造意义。结果表明，新丰街岩体由二云母花岗岩和黑云母花岗组成；两者均形成于晚侏罗世
（~148 Ma）；二云母花岗岩SiO2含量为75.71%~78.36%，为弱过铝质—强过铝质岩石，属高钾钙碱性系列，Mg#变化于0.26~
0.34，具有较低的Ga/Al比值（绝大部分<2.6×10-4）和较低的Zr+Nb+Ce+Y含量（<350×10-6），全岩εNd(t)为-10~-8.2，锆石原
位εHf(t)为-15.7~-9.4；黑云母花岗岩SiO2含量为71.25%~74.41%，主要为准铝质—弱过铝质岩石，也属于高钾钙碱性系列，
Mg#变化于0.32~0.37，同样具有较低的Ga/Al比值（绝大部分<2.6×10-4）和较低的Zr+Nb+Ce+Y含量（<350×10-6），全岩初始
87Sr/86Sr比值为0.7136~0.7153，εNd(t)为-10.0~-8.9，锆石原位εHf(t)值为-16.5~-10.9。通过综合研究认为二云母花岗岩具有S
型花岗岩特征，是由下地壳中变质泥岩在相对较低温度下发生部分熔融而形成的；黑云母花岗岩具有I型花岗岩特征，是由下
地壳中长英质火成岩在相对较高温度下发生部分熔融而形成的。岩体侵位于由古太平洋板块俯冲引起的陆缘弧构造环境。

关键词: 新丰街岩体；江西中部；LA-ICP-MS锆石U-Pb年龄；Sr-Nd-Hf同位素；S型和I型花岗岩

Abstract:

In this study, we present detailed LA-ICP-MS zircon U-Pb chronology, major and trace elements, and Sr-Nd-Hf isotopic
data for the Xinfengjie pluton in central Jiangxi province, and discuss its petrogenesis and tectonic implications. Our results show
that the Xinfengjie granites are composed of two-mica granites and biotite granites, both of which were formed in late Jurassic (ca.
148 Ma). The two-mica granites have SiO2 contents of 75.71~78.36%. They are weakly peraluminous to strongly peraluminous rocks,
and belong to high-K calc-alkaline series. Their Mg# vary from 0.26 to 0.34, and they have low Ga/Al ratios (mostly < 2.6×10-4) and low
Zr+Nb+Ce+Y contents (<350×10-6). They have whole-rack εNd(t) of -10~-8.2, and zircon in-situ εHf(t) of -15.7~-9.4. The biotite
granites have SiO2 contents of 71.25~74.41% . They are metaluminous to weakly peraluminous rocks, and also belong to high-Kcalc-alkaline series. Their Mg# vary from 0.32 to 0.37, and they also have low Ga/Al ratios (mostly < 2.6×10-4) and low Zr+Nb+Ce+Y
contents (<350×10-6). They have initial 87Sr/86Sr ratios of 0.7136~0.7153, εNd(t) of -10.0~-8.9, and zircon in-situ εHf(t ) of -16.5~-10.9.
Through our comprehensive research, we consider that the two-mica granites show characteristics of S-type granites, and were formed at
lower temperature by partial melting of meta-pelite in the lower crust, while the biotite granites exhibit I-type affinity, and were formed
at higher temperature by partial melting of felsic rocks in the lower crust. This pluton emplaced in a continental-arc tectonic regime
which was induced by the subduction of the paleo-pacific plate.

Key words: Xinfengjie granites, Central Jiangxi province, LA-ICP-MS zircon U-Pb age, Sr-Nd-Hf isotopes, S- and I-type granites

朱书奇，姜耀辉*，王国昌，倪春雨，青龙. 江西中部新丰街花岗质岩体LA-ICP-MS锆石U-Pb年代学、元素和Sr-Nd-Hf同位素地球化学特征及岩石成因[J]. J4, 2016, 22(3): 431-.

ZHU Shuqi, JIANG Yaohui*, WANG Guochang, NI Chunyu, QING Long. LA-ICP-MS Zircon U-Pb Geochronology, Elemental and Sr-Nd-Hf Isotopic Geochemistry of the Xinfengjie Granitic Intrusion in Central Jiangxi Province, SE China, and Its Petrogenesis[J]. J4, 2016, 22(3): 431-.