干旱区生态环境知识资源中心(Arid): Paleomagnetism and Ar-40/Ar-39 chronology of ignimbrites and lava flows, Central Volcanic Zone, Northern Chile

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DOI	10.1016/j.jsames.2020.103037
	Paleomagnetism and Ar-40/Ar-39 chronology of ignimbrites and lava flows, Central Volcanic Zone, Northern Chile
	Brown, Laurie; Singer, Brad S.; Barquero-Molina, Miriam
通讯作者	Brown, L (corresponding author), Univ Massachusetts, Dept Geosci, Amherst, MA 01003 USA.
来源期刊	JOURNAL OF SOUTH AMERICAN EARTH SCIENCES
ISSN	0895-9811
EISSN	1873-0647
出版年	2021
卷号	106
英文摘要	New Ar-40/Ar-39 ages and paleomagnetic data are presented from a wide range of ignimbrites and lava flows from the region east of the Atacama Desert in the northern Chilean part of Central Volcanic Zone of the Andes. Eight dacitic to rhyolitic ignimbrites, 12 lava flows and one shallow intrusion were dated by the Ar-40/Ar-39 incremental heating method, and are the first Ar-40/Ar-39 ages reported for these units. Ignimbrites range in age from 4.2 Ma to 0.5 Ma, with the similar to 100 km(3) Puripicar ignimbrite dated at 4.18 +/- 0.02 Ma, the similar to 2500 km(3) Atana ignimbrite, one of the largest ignimbrites in the world, at 3.99 +/- 0.02 Ma, and the Purico ignimbrite at 0.99 +/- 0.03 Ma. The new Ar-40/Ar-39 ages fall within the uncertainty limits of published K-Ar dates for the Purico, Patao and Puripicar tuffs but are different at the 95% confidence level for Atana and Talabre tuffs. Isochron ages from the 12 lava flows range from 3.5 Ma to 0.1 Ma, with 11 of the flows younger than 2.5 Ma. One lava sample and the shallow intrusion are from the Plio-Pleistocene magnetite-rich El Laco volcanic complex, and give ages of 2.18 +/- 0.03 Ma and 1.83 +/- 0.09 Ma respectively. Paleomagnetic directions from 49 sites (23 ignimbrites and 26 lava flows) provide a mean direction of I = -43.8 degrees, D = 352.7 degrees with alpha(95) = 10.0 degrees, and a corresponding mean pole position of - 81.1 degrees and 179.1 degrees. Normal directions are predominantly from lava flows and have steeper than expected inclinations (Delta I = 15.3 degrees) whereas reverse sites are mostly ignimbrites and yield directions close to the geo-axial dipole field (Delta I =3.6 degrees). Paleosecular variation studies on a selection of 39 sites yield an angular standard deviation of site poles about the mean pole of 18.5 degrees, considerably larger than predicted by current models of magnetic field variation with latitude.
英文关键词	Geochronology Paleomagnetism Paleosecular variation Altiplano-Puna volcanic complex
类型	Article
语种	英语
收录类别	SCI-E
WOS记录号	WOS:000612682600002
WOS关键词	TRANSITIONALLY MAGNETIZED LAVAS ; TIME-AVERAGED FIELD ; CENTRAL ANDES ; PALEOSECULAR VARIATION ; SOUTHERN-HEMISPHERE ; GEOMAGNETIC-FIELD ; EVOLUTION ; COMPLEX ; GEOCHRONOLOGY ; TIMESCALE
WOS类目	Geosciences, Multidisciplinary
WOS研究方向	Geology
资源类型	期刊论文
条目标识符	http://119.78.100.177/qdio/handle/2XILL650/348035
作者单位	[Brown, Laurie] Univ Massachusetts, Dept Geosci, Amherst, MA 01003 USA; [Singer, Brad S.; Barquero-Molina, Miriam] Univ Wisconsin, Dept Geosci, Madison, WI 53706 USA; [Barquero-Molina, Miriam] Univ Missouri, Geol Sci, Columbia, MO 65203 USA
推荐引用方式 GB/T 7714	Brown, Laurie,Singer, Brad S.,Barquero-Molina, Miriam. Paleomagnetism and Ar-40/Ar-39 chronology of ignimbrites and lava flows, Central Volcanic Zone, Northern Chile[J],2021,106.
APA	Brown, Laurie,Singer, Brad S.,&Barquero-Molina, Miriam.(2021).Paleomagnetism and Ar-40/Ar-39 chronology of ignimbrites and lava flows, Central Volcanic Zone, Northern Chile.JOURNAL OF SOUTH AMERICAN EARTH SCIENCES,106.
MLA	Brown, Laurie,et al."Paleomagnetism and Ar-40/Ar-39 chronology of ignimbrites and lava flows, Central Volcanic Zone, Northern Chile".JOURNAL OF SOUTH AMERICAN EARTH SCIENCES 106(2021).