干旱区生态环境知识资源中心(Arid): Temporal and Petrogenetic Links Between Mesoproterozoic Alkaline and Carbonatite Magmas at Mountain Pass, California

Arid

DOI	10.5382/econgeo.4848
	Temporal and Petrogenetic Links Between Mesoproterozoic Alkaline and Carbonatite Magmas at Mountain Pass, California
	Watts, Kathryn E.; Haxel, Gordon B.; Miller, David M.
通讯作者	Watts, KE (corresponding author), US Geol Survey, 904 West Riverside Ave, Spokane, WA 99201 USA.
来源期刊	ECONOMIC GEOLOGY
ISSN	0361-0128
EISSN	1554-0774
出版年	2022
卷号	117 期号:1 页码:1-24
英文摘要	Mountain Pass is the site of the most economically important rare earth element (REE) deposit in the United States. Mesoproterozoic alkaline intrusions are spatiotemporally associated with a composite carbonatite stock that hosts REE ore. Understanding the genesis of the alkaline and carbonatite magmas is an essential scientific goal for a society in which critical minerals are in high demand and will continue to be so for the foreseeable future. We present an ion microprobe study of zircon crystals in shonkinite and syenite intrusions to establish geochronological and geochemical constraints on the igneous underpinnings of the Mountain Pass REE deposit. Silicate whole-rock compositions occupy a broad spectrum (50-72 wt % SiO2), are ultrapotassic (6-9 wt % K2O; K2O/Na2O = 2-9), and have highly elevated concentrations of REEs (La 500-1,100 x chondritic). Zircon concordia Pb-206/U-238-Pb-207/U-235 ages determined for shonkinite and syenite units are 1409 +/- 8, 1409 +/- 12, 1410 +/- 8, and 1415 +/- 6 Ma (2 sigma). Most shonkinite dikes are dominated by inherited Paleoproterozoic xenocrysts, but there are sparse primary zircons with Pb-207/Pb-206 ages of 1390-1380 +/- 15 Ma for the youngest grains. Our new zircon U-Pb ages for shonkinite and syenite units overlap published monazite Th-Pb ages for the carbonatite orebody and a smaller carbonatite dike. Inherited zircons in shonkinite and syenite units are ubiquitous and have a multimodal distribution of Pb-207/Pb-206 ages that cluster in the range of 1785-1600 +/- 10-30 Ma. Primary zircons have generally lower Hf (<11,000 ppm) and higher Eu/Eu* (>0.6), Th (>300 ppm), Th/U (>1), and Ti-in-zircon temperatures (>800 degrees C) than inherited zircons. Oxygen isotope data reveals a large range in delta O-18 values for primary zircons, from mantle (5-5.5 parts per thousand) to crustal and supracrustal (7-9 parts per thousand). A couple of low-delta O-18 outliers (2 parts per thousand) point to a component of shallow crust altered by meteoric water. The delta O-18 range of inherited zircons (5-10 parts per thousand) overlaps that of the primary zircons. Our study supports a model in which alkaline and carbonatite magmatism occurred over tens of millions of years, repeatedly tapping a metasomatized mantle source, which endowed magmas with elevated REEs and other diagnostic components (e.g., F, Ba). Though this metasomatized mantle region existed for the duration of Mountain Pass magmatism, it probably did not predate magmatism by substantial geologic time (>100 m.y.), based on the similarity of 1500 Ma zircons with the dominantly 1800-1600 Ma inherited zircons, as opposed to the 1450-1350 Ma primary zircons. Mountain Pass magmas had diverse crustal inputs from assimilation of Paleoproterozoic and Mesoproterozoic igneous, metaigneous, and metasedimentary rocks. Crustal assimilation is only apparent from high spatial resolution zircon analyses and underscores the need for mineral-scale approaches in understanding the genesis of the Mountain Pass system.
类型	Article
语种	英语
开放获取类型	hybrid
收录类别	SCI-E
WOS记录号	WOS:000722744600001
WOS关键词	PROTEROZOIC CRUSTAL EVOLUTION ; RARE-EARTH CARBONATITE ; EASTERN MOJAVE DESERT ; ORIGIN ; ZIRCON ; TRACE ; GEOCHRONOLOGY ; ROCKS ; KIMBERLITE ; MICROPROBE
WOS类目	Geochemistry & Geophysics ; Mineralogy
WOS研究方向	Geochemistry & Geophysics ; Mineralogy
资源类型	期刊论文
条目标识符	http://119.78.100.177/qdio/handle/2XILL650/374420
作者单位	[Watts, Kathryn E.] US Geol Survey, 904 West Riverside Ave, Spokane, WA 99201 USA; [Haxel, Gordon B.] US Geol Survey, 2255 North Gemini Dr, Flagstaff, AZ 86001 USA; [Miller, David M.] US Geol Survey, 350 North Akron Rd, Moffett Field, CA 94025 USA
推荐引用方式 GB/T 7714	Watts, Kathryn E.,Haxel, Gordon B.,Miller, David M.. Temporal and Petrogenetic Links Between Mesoproterozoic Alkaline and Carbonatite Magmas at Mountain Pass, California[J],2022,117(1):1-24.
APA	Watts, Kathryn E.,Haxel, Gordon B.,&Miller, David M..(2022).Temporal and Petrogenetic Links Between Mesoproterozoic Alkaline and Carbonatite Magmas at Mountain Pass, California.ECONOMIC GEOLOGY,117(1),1-24.
MLA	Watts, Kathryn E.,et al."Temporal and Petrogenetic Links Between Mesoproterozoic Alkaline and Carbonatite Magmas at Mountain Pass, California".ECONOMIC GEOLOGY 117.1(2022):1-24.