DOI: 10.1016/j.epsl.2017.10.021
Scopus记录号: 2-s2.0-85033663977
论文题名: Timescales between mantle metasomatism and kimberlite ascent indicated by diffusion profiles in garnet crystals from peridotite xenoliths
作者: Jollands M.C. ; Hanger B.J. ; Yaxley G.M. ; Hermann J. ; Kilburn M.R.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2018
卷: 481 起始页码: 143
结束页码: 153
语种: 英语
英文关键词: diffusion
; garnet
; kimberlite
; mantle metasomatism
; NanoSIMS
Scopus关键词: Aluminum
; Calcium
; Diffusion
; Garnets
; Manganese
; Mass spectrometry
; Mineralogy
; Secondary ion mass spectrometry
; Diffusion profiles
; Electron microprobes
; kimberlite
; Mantle metasomatism
; Metasomatic process
; Multi-component diffusion
; NanoSIMS
; Peridotite xenoliths
; Volcanic rocks
; crystal
; diffusion
; garnet
; kimberlite
; mantle structure
; mass spectrometry
; metasomatism
; peridotite
; xenolith
; South Africa
英文摘要: Rare garnet crystals from a peridotite xenolith from the Wesselton kimberlite, South Africa, have distinct zones related to two separate episodes of mantle metasomatism. The garnet cores were firstly depleted through melt extraction, then equilibrated during metasomatism by a potentially diamond-forming carbonate-bearing or proto-kimberlitic fluid at 1100–1300 °C and 4.5–5.5 GPa. The garnet rim chemistry, in contrast, is consistent with later overgrowth in equilibrium with a kimberlite at around 1025±25°C and 4.2±0.5 GPa. This suggests that the rock was physically moved upwards by up to tens of kilometres between the two metasomatic episodes. Preserved high Ca, Al and Cr contents in orthopyroxenes suggest this uplift was tectonic, rather than magmatic. Diffusion profiles were measured over the transitions between garnet cores and rims using electron microprobe (Mg, Ca, Fe for modelling, plus Cr, Mn, Ti, Na, Al) and nano Secondary Ion Mass Spectrometry (NanoSIMS; 89Y, along with 23Na, Ca, Cr, Fe, Mn and Ti) analyses. The short profile lengths (generally <10 μm) and low Y concentrations (0.2–60 ppm) make the NanoSIMS approach preferable. Diffusion profiles at the interface between the zones yield constraints on the timescale between the second metasomatic event and eruption of the kimberlite magma that brought the xenolith to the surface. The time taken to form the diffusion profiles is on the order of 25 days to 400 yr, primarily based on modelling of Y diffusion along with Ca, Fe and Mg (multicomponent diffusion) profiles. These timescales are too long to be produced by the interaction of the mantle xenolith with the host kimberlite magma during a single-stage ascent to the crust (hours to days). The samples offer a rare opportunity to study metasomatic processes associated with failed eruption attempts in the cratonic lithosphere. © 2017 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/110179
Appears in Collections: 影响、适应和脆弱性 气候变化事实与影响
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作者单位: Research School of Earth Sciences, Australian National University, Mills Road, Canberra, ACT 2601, Australia; Institute of Earth Sciences, University of Lausanne, Géopolis building, Lausanne, 1015, Switzerland; Boone Pickens School of Geology, Noble Research Centre, Oklahoma State University, Stillwater, OK 74078, United States; Institute of Earth Sciences, University of Bern, Balzerstrasse 1+3, Bern, 3012, Switzerland; Centre for Microscopy, Characterisation and Analysis, University of Western Australia, Crawley, WA 6009, Australia
Recommended Citation:
Jollands M.C.,Hanger B.J.,Yaxley G.M.,et al. Timescales between mantle metasomatism and kimberlite ascent indicated by diffusion profiles in garnet crystals from peridotite xenoliths[J]. Earth and Planetary Science Letters,2018-01-01,481