Fe-(oxyhydr)oxide participation in REE enrichment in early Cambrian phosphorites from South China: Evidence from in-situ geochemical analysis

被引：3

作者：

Yang, Haiying ^{[1
,3
,4
]}

Zhao, Zhifang ^{[1
,3
,4
]}

Fan, Haifeng ^{[2
]}

Zeng, Min ^{[1
,3
,4
]}

Xiao, Jiafei ^{[2
]}

Liu, Xiqiang ^{[2
]}

Wu, Shengwei ^{[2
]}

Chao, Jiangqin ^{[1
,3
,4
]}

Xia, Yong ^{[2
]}

机构：

[1] Yunnan Univ, Sch Earth Sci, Kunming 650500, Peoples R China

[2] Chinese Acad Sci, State Key Lab Ore Deposit Geochem, Inst Geochem, Guiyang 550081, Peoples R China

[3] Yunnan Int Joint Lab China Laos Bangladesh Myanmar, Kunming 650500, Peoples R China

[4] MNR Key Lab Sanjiang Met & Resources Explorat & Ut, Kunming 650051, Peoples R China

来源：

JOURNAL OF ASIAN EARTH SCIENCES | 2024年 / 259卷

基金：

中国国家自然科学基金;

关键词：

REE-rich phosphorite; Early Cambrian; In -situ analysis; Fe/Mn (oxyhydr)oxides; South China; RARE-EARTH-ELEMENTS; PGE-AU MINERALIZATION; BLACK SHALES; FERROMANGANESE CRUSTS; TRACE-ELEMENTS; PORE WATERS; MN-OXIDES; YTTRIUM; DEPOSITS; INSIGHTS;

D O I：

10.1016/j.jseaes.2023.105910

中图分类号：

P [天文学、地球科学];

学科分类号：

07 ;

摘要：

Marine phosphorites have shown extraordinary REE potential. Enrichment mechanisms have been investigated as yet, however, the roles of Fe/Mn (oxyhydr)oxides in REE enrichment were poorly known. In this paper, we report new data for early Cambrian phosphorites in South China with a particular focus on REE enrichment and Fe-redox cycling. Phosphorites from the Cambrian Gezhongwu occur in the upper and lower units. The phosphorites contain a large number of of Fe (oxyhydr)oxides, especially those in the upper unit. SEM and laser Raman show that Fe (oxyhydr)oxides have a gray rim and a bright core, attributed to transformation from hematite to goethite during the weathering. In-situ elemental analyses show Fe (oxyhydr)oxides have PAASnormalized REE patterns depleted in LREE and enriched in HREE with negative to positive Eu anomalies and positive Y anomalies. However, two patterns are clearly distinguished according to Ce anomalies and these are related to the origins of Fe-(oxyhydr)oxides: hydrothermal Fe (oxyhydr)oxides with negative Ce anomalies and hydrogenic ones with positive Ce anomalies. The role of Fe (oxyhydr)oxides played in REE enrichment was controlled by Fe-redox pumping. In this process, Fe (oxyhydr)oxides adsorbed REEs in oxic water columns; after precipitating to suboxic/anoxic conditions, the absorbed REEs were released into porewater. Francolites subsequently formed and captured REEs during early diagenesis. Even though additional evidence is required, our investigations were significant in conforming the origins of Fe/Mn (oxyhydr)oxides and their role in REE enrichment in marine phosphorites.

引用

页数：21