摘要
阳新岩体是鄂东南地区出露规模最大的岩体,也是鄂东南地区矿产最集中的地段。该岩体主要由石英闪长岩和小规模的黑云石英闪长岩组成。本文利用LA-ICP-MS锆石U-Pb法对阳新岩体进行了精确的年龄测定及相应的Lu-Hf同位素分析。结果表明,阳新岩体形成于143~139 Ma之间,且主体岩性石英闪长岩侵位略早于黑云石英闪长岩。它们均是鄂东南地区岩浆活动高峰期的产物。锆石Ti温度计计算结果显示,石英闪长岩的形成温度主要分布在787~876℃之间,黑云石英闪长岩的形成温度主要分布在686~805℃之间。锆石Hf同位素分析表明,阳新石英闪长岩的ε_(Hf)(t)值为-11.42^-3.31,黑云石英闪长岩的ε_(Hf)(t)值明显偏低且分布范围较大,为-21.75^-1.44。结合岩体元素地球化学、Sr-Nd同位素以及矿物化学等方面的特征,认为阳新岩体应主要来源于富集岩石圈地幔,且在成岩过程中伴随一定程度的分离结晶和同化混染作用。其中,石英闪长岩结晶略早,形成温度较高,黑云石英闪长岩结晶稍晚,形成温度较低,且黑云石英闪长岩的源区较石英闪长岩有更多壳源物质的加入。
The Yangxin pluton is the largest intrusion in southeast Hubei Province, and is also the section in which mineral resources
are the most concentrated. The complex is mainly composed of quartz diorites and small-scale biotite quartz diorites. This paper
presents high-precision zircon U-Pb ages and Hf isotopes of the Yangxin intrusion. The result indicates that its emplacement took place
around 143~139 Ma, and the quartz diorites were emplaced earlier than the biotite quartz diorites. Both of them were products of
magmatic activities in the peak period of this area. The calculation results of Ti-in-zircon thermometer show that the quartz diorites
were mainly formed in the temperature ranging from 787℃ to 876℃ , and the biotite quartz diorites were mainly formed in the
temperature ranging from 686℃ to 805℃. The zircon Hf isotopic data show that εHf（t） values of the quartz diorites range from-11.42
to-3.31, and εHf（t） values of the biotite quartz diorites are obviously lower and have a wider distribution （from -21.75 to -1.44）. Combined
with geochemical, Sr and Nd isotopic and mineral chemical characteristics, both quartz diorites and biotite quartz diorites were likely
derived from enriched lithospheric mantle, as well as fractional crystallization and assimilation followed. Moreover, quartz diorites
crystallized earlier in higher temperature, while the biotite quartz diorites crystallized later in the lower temperature with addition of
more crustal materials.
出处
《高校地质学报》
CAS
CSCD
北大核心
2016年第3期443-458,共16页
Geological Journal of China Universities
基金
中国地质调查局地质调查资助项目(1212011120863
12120114005901
121201009000150012)
