Oxidation state of Paleozoic subcontinental lithospheric mantle below the Pali Aike volcanic field in southernmost Patagonia
Oxidation state of Paleozoic subcontinental lithospheric mantle below the Pali Aike volcanic field in southernmost Patagonia
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巴塔哥尼亚最南端巴利艾克火山田下方古生代次大陆岩石圈地幔氧化态
DOI：
10.1016/j.lithos.2008.02.009
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发表时间：
2008-09
期刊：
影响因子：
3.5
通讯作者：
Stern, Charles R.
中科院分区：
文献类型：
--
作者：
Wang, Jian;Hattori, Keiko H.;Li, Jianping;Stern, Charles R.
巴塔哥尼亚最南端第四纪巴里艾克碱性玄武岩中的地幔包体包括含或不含石榴石的二辉橄榄岩和方辉橄榄岩。所有包体的fO2值在铁闪石-磁铁矿-石英缓冲层(Fmq−0.33)以下的0.33个对数单位到fmq+0.75之间，与深海橄榄岩的fO2值重叠。结合岩石矿物组成的fO2数据表明，巴里艾克以下的陆下岩石圈地幔(SCLM)是大洋岩石圈的吸积作用形成的。大洋增生可能发生在中晚古生代，当时巴塔哥尼亚南部地体沿着冈瓦那西南边缘形成。石榴石中残留的尖晶石包裹体表明，石榴石相橄榄岩是由尖晶石相橄榄岩形成的，很可能是对吸积过程中压力增加的响应。石榴石和尖晶石相橄榄岩的可比fO2表明，这种尖晶石-石榴石转变并不伴随着fO2的变化。软流圈熔体通过板条窗口的交代作用导致含钛矿物的形成，块状岩石和矿物中镁的降低和钛的富集化。在极端情况下，斜方辉石取代橄榄石形成斜方辉石。由于未交代(Fmq−0.23至+0.48)和交代(Fmq−0.33至+0.75)样品之间观察到相似的氧化状态，因此这种交代作用与fO2没有显著变化。这是由与交代前的−相似的软流圈熔体的fO2(FmqSCLm)解释的。
Mantle xenoliths in the Quaternary Pali Aike alkaline basalts of southernmost Patagonia include lherzolites and harzburgites with and without garnet. The values of fO2for all xenoliths range from 0.33 logarithmic unit below the fayalite–magnetite–quartz buffer (FMQ−0.33) to FMQ+0.75, which overlap those for abyssal peridotites. The fO2data, together with the bulk rock and mineral compositions, suggest that the subcontinental lithospheric mantle (SCLM) below Pali Aike formed through the accretion of oceanic lithosphere. The oceanic accretion likely occurred in mid to late Paleozoic time when the southern Patagonian terrane formed along the southwest margin of Gondwana. Relict spinel inclusions in garnet suggest that garnet-facies peridotites formed from spinel-facies peridotites most likely in response to pressure increase during the accretion. Comparable fO2for garnet- and spinel-facies peridotites suggests that this spinel-garnet transformation was not accompanied by changes in fO2. Metasomatism by asthenosphere-derived melt through a slab window resulted in the formation of Ti-bearing minerals, and lowering of Mg and enrichment of Ti in bulk rocks and minerals. The replacement of olivine by orthopyroxene formed orthopyroxenites in extreme cases. No significant change in fO2is associated with this metasomatism since similar oxidation state is observed between un-metasomatized (FMQ−0.23 to +0.48) and metasomatized (FMQ−0.33 to +0.75) samples. This is explained by the fO2of the asthenospheric melt (~FMQ−0.50) similar to the SCLM prior to the metasomatism.
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影响因子：
3.1
作者：
M. McCanta;M. Dyar;M. Rutherford;J. Delaney
通讯作者：
M. McCanta;M. Dyar;M. Rutherford;J. Delaney
影响因子：
3.1
作者：
J. Selverstone;C. Stern
通讯作者：
J. Selverstone;C. Stern
影响因子：
3.9
作者：
Y. Niu
通讯作者：
Y. Niu
DOI：
10.1144/gsl.sp.2005.246.01.12
发表时间：
2005
期刊：
Geological Society, London, Special Publications
影响因子：
--
作者：
A. Rapalini
通讯作者：
A. Rapalini
影响因子：
1.8
作者：
W. Gosen
通讯作者：
W. Gosen