Oxidation state of europium in scheelite: Tracking fluid-rock interaction in gold deposits

被引：160

作者：

Brugger, Joel ^{[1
,2
]}

Etschmann, Barbara ^{[3
,4
]}

Pownceby, Mark ^{[5
]}

Liu, Weihua ^{[3
]}

Grundler, Pascal ^{[1
,2
]}

Brewe, Dale ^{[6
]}

机构：

[1] Univ Adelaide, S Australian Museum, Adelaide, SA 5005, Australia

[2] Univ Adelaide, Sch Earth & Environm Sci, Adelaide, SA 5005, Australia

[3] Univ Melbourne, CSIRO Explorat & Min, Sch Phys, Melbourne, Vic 3010, Australia

[4] Univ Tasmania, CODES Ctr Excellence, Hobart, Tas 7001, Australia

[5] CSIRO Minerals, Clayton, Vic 3168, Australia

[6] Argonne Natl Lab, Adv Photon Source, Argonne, IL 60439 USA

来源：

CHEMICAL GEOLOGY | 2008年 / 257卷 / 1-2期

基金：

澳大利亚研究理事会;

关键词：

Hydrothermal fluid; Rare earth element geochemistry; Europium; Gold deposit; Synchrotron radiation; Scheelite;

D O I：

10.1016/j.chemgeo.2008.08.003

中图分类号：

P3 [地球物理学]; P59 [地球化学];

学科分类号：

0708 ; 070902 ;

摘要：

We used mu-XANES spectroscopy to measure the oxidation state of europium in-situ at near-mu m resolution ill hydrothermal scheelite from the giant Archean gold deposits of Kalgoorlie, Western Australia. By combining these measurements with mu-XRF imaging, it is possible to distinguish inhomogeneities in Eu2+/Eu3+ ratios that developed during mineral precipitation from the effects of subsequent hydrothermal alteration and weathering. Thermodynamic analysis reveals that under the conditions typical of the formation of many Au deposits, the Eu2+Eu3+ ratio in the hydrothermal fluid is highly sensitive to pH. The range in pH calculated from the Eu2+/Eu3+ ratios in the analyzed scheelite corresponds to a maximum in Au solubility under the ore-forming conditions, and suggests buffering of pH by the CO2(aq)-rich fluid. The primary heterogeneity of the Karlgoorlie scheelite most likely results from pH oscillating between fluid- and rock-buffered conditions, and reflects the dynamics of the hydrothermal system. (C) 2008 Elsevier B.V. All rights reserved.

引用

页码：26 / 33

页数：8

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