摘要
彭山锡多金属矿集区成矿区划位于长江中下游成矿带与江南钨多金属成矿带的过渡部位。以前研究认为与锡大规模成矿有关的花岗岩通常为高分异的过铝质岩浆,但是关于Sn在还原性岩浆中与矿物相的分配和迁移的氧逸度阈值犹未可知,锡与钨在赣北地区成矿的分带分区(解耦)究竟是受岩浆源区特征的控制还是为氧逸度所制约,目前尚不清楚。本文对区内花岗岩岩石成因、锡的来源、岩浆演化早期的氧化还原条件,及其对锡在岩浆中的分配、萃取和迁移的控制过程开展了研究,即对彭山岩体进行了精细的锆石原位微区分析测试。结果显示,锆石P含量普遍较高,结合P(∑REE+Y)拟合的3条趋势线的斜率分别为0.91、0.85和0.81,与S型花岗岩(∑REE+Y)<1.15×P演变规律相符。在Eu/Eu^(*)Yb N/Gd N关系图解中未显示出与Ti分离曲线的同步协变关系,相反,各组岩石均显示为负相关关系,说明3组锆石Eu/Eu^(*)的比值受榍石与斜长石的共结晶的影响较为有限。依据Hf Ce^(4+)/Ce^(3+)zircon和Ti Ce^(4+)/Ce^(3+)zircon关系图,白云母花岗岩数据区域均位于趋势线末端,与黑云母二长花岗岩和花岗斑岩相比,显示出更低的氧逸度特点。Eu/Eu^(*)与Ce^(4+)/Ce^(3+)zircon比值在各岩石单元中所表现出的还原程度是相耦合的,即组成彭山岩体的3个岩石单元——成矿后花岗斑岩岩脉、黑云母二长花岗岩岩基和白云母花岗岩成矿岩株,其锆石Eu异常(Eu/Eu^(*))和Ce^(4+)与Ce^(3+)比值(Ce^(4+)/Ce^(3+)zircon)呈逐渐递减趋势。双桥山群中1.5~1.3 Ga砂泥质沉积岩与细碧角斑岩系组成的海相古火山喷发沉积建造,可能提供了本区Sn的初始来源。白云母花岗岩成矿岩株的氧逸度显著低于大湖塘石门寺矿床的花岗岩,锆石微量元素揭示了富锡岩浆演化比富钨岩浆具有更低的氧逸度。
The Pengshan tin-polymetallic metallogenic ore field is situated at the transitional junction of the Middle Lower Yangtze metallogenic belt and the Jiangnan tungsten-polymetallic metallogenic belt.Previous research has indicated that granites associated with large-scale tin mineralization typically stem from highly differentiated peraluminous magmas.However,the precise threshold of oxygen fugacity governing the distribution and migration of tin with mineral phases in reducing magmas remains unknown.It is unclear whether the zonation of tin and tungsten mineralization in northern Jiangxi Province is controlled by the characteristics of the magmatic source or by oxygen fugacity.This study delves into the petrogenesis of granites,the tin source,the redox conditions during the early stages of magmatic evolution,and their influence on the distribution,extraction,and migration of tin within the magma.Through detailed in situ zircon microanalysis of the Pengshan pluton,the findings reveal that the P content of zircon is generally high.The slope of three trend lines fitted by P-(∑REE+Y)is 0.91,0.85,and 0.81,respectively,aligning with the characteristics of S-type granites(∑REE+Y)<1.15×P.In the Eu/Eu^(*)Yb N/Gd N diagram,a negative correlation is observed in all rock groups,indicating that the Eu/Eu^(*)ratios of zircons are constrained by the co-crystallization of titanite and plagioclase.The Hf Ce^(4+)/Ce^(3+)zircon and Ti-zircon ratios reflect the degree of reduction in each rock unit within the Pengshan pluton.The zircon Eu anomaly(Eu/Eu^(*))and Ce^(4+)/Ce^(3+)zircon ratio exhibit decreasing trends across the three rock units comprising the Pengshan pluton:post-metallogenic granite porphyry→biotite monzogranite batholith→metallogenic muscovite granite.The sandy-argillaceous sedimentary rocks and spilite formed from marine paleo-volcanic eruptive deposits around 1.5 to 1.3 billion years ago likely served as the initial source of tin in the region.The oxygen fugacity of the muscovite granite is lower than that o
作者
尹青青
唐菊兴
项新葵
赵晓彦
汪方跃
徐裕敏
郭虎
余振东
谢金玲
代晶晶
彭勃
YIN Qingqing;TANG Juxing;XIANG Xinkui;ZHAO Xiaoyan;WANG Fangyue;XU Yumin;GUO Hu;YU Zhendong;XIE Jinling;DAI Jingjing;PENG Bo(Faculty of Geosciences and Engineering,Southwest Jiaotong University,Chengdu 611756,China;MNR Key Laboratory of Metallogeny and Mineral Assessment,Institute of Mineral Resources,Chinese Academy of Geological Sciences,Beijing 100037,China;The Third Geological Brigade of Jiangxi Geological Bureau,Jiujiang 332100,China;School of Resources and Environmental Engineering,Hefei University of Technology,Hefei 230009,China;Laboratory of Non-Fossil Energy Minerals,Tianjin Center of China Geological Survey,Tianjin 300170,China)
出处
《地学前缘》
EI
CAS
CSCD
北大核心
2024年第3期133-149,共17页
Earth Science Frontiers
基金
国家重点研发计划项目(2022YFC2905003)
中国地质科学院基本科研业务费项目(KK2018)
江西省科学技术厅国家科技奖后备培育项目(20203AEI91004)。
关键词
还原性
S型花岗岩
Sn富集
锆石
赣北
彭山
reductivity
S-type granite
Sn enrichment
zircon
northern Jiangxi Province
Pengshan
