气候变化领域集成服务门户(CCPortal): Thermodynamic Constraints on REE Mineral Paragenesis in the Bayan Obo REE-Nb-Fe Deposit, China

CCPortal

DOI	10.3390/min10060495
	Thermodynamic Constraints on REE Mineral Paragenesis in the Bayan Obo REE-Nb-Fe Deposit, China
	Liu, Shang; Ding, Lin; Fan, Hong-Rui
通讯作者	Liu, S (通讯作者)
发表日期	2020
EISSN	2075-163X
卷号	10 期号:6
英文摘要	Hydrothermal processes have played a significant role in rare earth element (REE) precipitation in the Bayan Obo REE-Nb-Fe deposit. The poor preservation of primary fluid inclusions and superposition or modification by multiphase hydrothermal activities have made identification of physico-chemical conditions of ore-forming fluids extremely difficult. Fortunately, with more and more reliable thermodynamic properties of aqueous REE species and REE minerals reported in recent years, a series of thermodynamic calculations are conducted in this study to provide constraints on REE precipitation in hydrothermal solutions, and provide an explanation of typical paragenesis of REE and gangue minerals at Bayan Obo. During the competition between fluocerite and monazite for LREE in the modelled solution (0.1 M HCl, 0.1 M HF and 0.1 M trichloride of light rare earth elements (LREE) from La to Sm), all LREE would eventually be hosted by monazite at a temperature over 300 degrees C, with continuous introduction of H3PO4. Additionally, monazite of heavier LREE would precipitate earlier, indicating that the Ce- and La-enriched monazite at Bayan Obo was crystallized from Ce and La pre-enriched hydrothermal fluids. The fractionation among LREE occurred before the ore-forming fluids infiltrating ore-hosting dolomite. When CO2(aq) was introduced to the aqueous system (model 1), bastnaesite would eventually and completely replace monazite-(Ce). Cooling of hot hydrothermal fluids (>400 degrees C) would significantly promote this replacement, with only about one third the cost of CO(2)for the entire replacement when temperature dropped from 430 degrees C to 400 degrees C. Sole dolomite addition (model 2) would make bastnaesite replace monazite and then be replaced by parisite. The monazite-(Ce) replaced by associated bastnaesite and apatite is an indicator of very hot hydrothermal fluids (>400 degrees C) and specific dolomite/fluid ratios (e.g., initial dolomite at 1 kbar: 0.049-0.068 M and 0.083-0.105 M at 400 degrees C and 430 degrees C). In hot solution (>430 degrees C) that continuously interacts with dolomite, apatite precipitates predating the bastnaesite, but it behaves oppositely at <400 degrees C. The former paragenesis is in accord with petrography observed in this study. Some mineral pairs, such as monazite-(Ce)-fluorite and monazite-(Ce)-parisite would never co-precipitate at any calculated temperature or pressure. Therefore, their association implies multiphase hydrothermal activities. Pressure variation would have rather limited influence on the paragenesis of REE minerals. However, temperature and fluid composition variation (e.g., CO2(aq), dolomite, H3PO4) would cause significantly different associations between REE and gangue minerals.
关键词	TEMPERATURE HEAT-CAPACITY RARE-EARTH-ELEMENTS ZIRCON U-PB INNER-MONGOLIA FLUID INCLUSION HYDROTHERMAL MOBILIZATION ORE-DEPOSIT CARBONATITE MONAZITE CRATON
英文关键词	REE precipitation; thermodynamic modelling; Bayan Obo REE-Nb-Fe deposit
语种	英语
WOS研究方向	Geochemistry & Geophysics ; Mineralogy ; Mining & Mineral Processing
WOS类目	Geochemistry & Geophysics ; Mineralogy ; Mining & Mineral Processing
WOS记录号	WOS:000553925900001
来源期刊	MINERALS
来源机构	中国科学院青藏高原研究所
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/259902
推荐引用方式 GB/T 7714	Liu, Shang,Ding, Lin,Fan, Hong-Rui. Thermodynamic Constraints on REE Mineral Paragenesis in the Bayan Obo REE-Nb-Fe Deposit, China[J]. 中国科学院青藏高原研究所,2020,10(6).
APA	Liu, Shang,Ding, Lin,&Fan, Hong-Rui.(2020).Thermodynamic Constraints on REE Mineral Paragenesis in the Bayan Obo REE-Nb-Fe Deposit, China.MINERALS,10(6).
MLA	Liu, Shang,et al."Thermodynamic Constraints on REE Mineral Paragenesis in the Bayan Obo REE-Nb-Fe Deposit, China".MINERALS 10.6(2020).