赣南宁都地区变质岩离子吸附型稀土矿床地球化学特征及找矿意义
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摘要
赣南浅变质岩离子吸附型稀土矿床是江西省近些年来新发现的稀土矿类型。文章主要研究赣南地区新元古代青白口纪库里组和神山组浅变质岩稀土矿点,通过野外地质调查和室内综合研究,总结了该类稀土矿床的地球化学特征。结果表明:该区浅变质岩以SiO_2含量中等、K_2O/Na_2O值较高、全碱含量中等、TFe_2O_3+MgO及CaO较低为特点;稀土元素总量较高,轻、重稀土元素分馏明显,轻稀土富集,Eu中等亏损,部分矿点已达到化学风化晚期阶段;各矿点风化壳的稀土元素配分模式与原岩类似,稀土元素富集程度主要受控于原岩稀土元素丰度和风化指数CIA。
Ion-absorbed rare earth deposits in low-grade metamorphic rock are new-type rare earth deposits found recently in Jiangxi Province. This study mainly focused on Neoproterozoic low-grade metamorphic rocks of the Shenshan and Kuli Formations in southern Jiangxi Province. Based on field geological survey and experimental tests,the geochemical characteristics of the deposits of this kind were summarized. The low-grade metamorphic rocks in the study area are characterized by moderate SiO_2 and total alkalicontents,high K_2 O/Na_2 O ratios,low TFe_2 O_3+MgO and CaO contents. They show high total ΣREE and ΣLREE,distinct LREE/HREE fractionation,as well as moderate Eu depletion. This study shows that parts of occurrences have been at the late stage of chemical weathering. Besides,the weathering crust in each rare earth ores display similar REE distribution patterns as their protoliths. The enrichment degree of REEs depends mainly on REE abundances and CIA values of protoliths. And weathering crust inherits the REE patterns of the protolith.
Ion-absorbed rare earth deposits in low-grade metamorphic rock are new-type rare earth deposits found recently in Jiangxi Province. This study mainly focused on Neoproterozoic low-grade metamorphic rocks of the Shenshan and Kuli Formations in southern Jiangxi Province. Based on field geological survey and experimental tests,the geochemical characteristics of the deposits of this kind were summarized. The low-grade metamorphic rocks in the study area are characterized by moderate SiO_2 and total alkalicontents,high K_2 O/Na_2 O ratios,low TFe_2 O_3+MgO and CaO contents. They show high total ΣREE and ΣLREE,distinct LREE/HREE fractionation,as well as moderate Eu depletion. This study shows that parts of occurrences have been at the late stage of chemical weathering. Besides,the weathering crust in each rare earth ores display similar REE distribution patterns as their protoliths. The enrichment degree of REEs depends mainly on REE abundances and CIA values of protoliths. And weathering crust inherits the REE patterns of the protolith.
引文
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[4]王登红,赵芝,于扬,等.离子吸附型稀土资源研究进展、存在问题及今后研究方向[J].岩矿测试,2013,32(5):796-802.
[5]吴学敏,周敏娟,罗喜成,等.江西西北部锂及稀有金属成矿条件及找矿潜力分析[J].华东地质,2016,37(4):275-283.
[6]范飞鹏,肖惠良,陈乐柱,等.南岭东段含稀土矿花岗岩体中暗色包体地质特征——以陂头岩体为例[J].华东地质,2016,37(1):36-44.
[7]杨岳清,赵芝,王成辉.风化壳离子吸附型稀土矿成矿作用及制约条件[J].地质论评,2016,62(B11):429-431.
[8]曾载淋,王先广,邹新勇,等.江西省宁都县葛藤嘴矿区稀土矿普查报告[R].赣州:江西省地质矿产勘查开发局赣南地质调查大队,2015.
[9]刘仁生,李强,龚敏,等.赣南变质岩风化壳离子吸附型稀土矿找矿新前景[J].地球科学前沿,2014,4(6):419-425.
[10]李奇,赵鹏坤.江西龙潭地区新型稀土矿找矿远景分析[J].科学与财富,2015,7(36):370-370.
[11]赵芝,王登红,邹新勇,等.江西宁都葛藤嘴浅变质岩离子吸附型稀土矿成矿模式[J].地质论评,2016,62(Z):421-422.
[12]张芳荣,吴富江,黄新曙.赣中南新元古代潭头群变质沉积岩物源及构造背景[J].东华理工大学学报:自然科学版,2009,32(2):134-140.
[13]舒良树,孙岩,王德滋,等.华南武功山中生代伸展构造[J].中国科学,1998,28(5):431-438.
[14]张芳荣.江西中—南部加里东期花岗岩地质地球化学特征及其成因[D].南京:南京大学,2011.
[15]江西省地质矿产局.江西省区域地质志[M].北京:地质出版社,1984.
[16]时国,郭福生,谢财富,等.赣中相山铀矿田基底变质岩原岩恢复及其形成环境[J].中国地质,2015,42(2):457-468.
[17]Nesbitt H W,Young G M.Early Proterozoic climates and plate motions inferred from major element chemistry of lutites[J].Nature,1982,299:715-717.
[18]冯连君,储雪蕾,张启锐,等.化学蚀变指数(CIA)及其在新元古代碎屑岩中的应用[J].地学前缘,2003,10(4):539-544.
[19]王数,东野光亮.地质学与地貌学教程[M].北京:中国农业大学出版社,2005.
[20]丘文.龙岩市万安稀土矿区变质岩风化壳离子吸附型稀土矿的发现及其找矿意义[J].世界有色金属,2017,(4):242-244.
[21]黄华谷,胡启锋,程亮开,等.广东禾尚田矿区新类型风化壳离子吸附型稀土矿的发现及意义[J].地质与勘探,2014,50(5):893-901.
[22]Taylor S R,Mc Clennan S M.The continental crust:Its composition and evolution:an examination of the geochemical record preserved in sedimentary rocks[J].Journal of Geology,1985,94(4):632-633.