The Sequoia kimberlite complex, central Slave Craton - A new superdeep diamond location

被引:0
|
作者
Carvalho, Luisa D. V. [1 ]
Doyle, Buddy [2 ]
Stachel, Thomas [1 ]
Stern, Richard [1 ]
Steele-MacInnis, Matthew [1 ]
Nestola, Fabrizio [3 ]
Pearson, D. Graham [1 ]
机构
[1] Univ Alberta, Dept Earth & Atmospher Sci, 1-26 ESB, Edmonton, AB T6G 2E3, Canada
[2] Arctic Star Explorat Corp, 1111 Melville St, Vancouver, BC V6E 3V6, Canada
[3] Univ Padua, Dipartimento Geosci, Via Gradenigo 6, I-35131 Padua, Italy
基金
加拿大自然科学与工程研究理事会;
关键词
Superdeep diamonds; C isotope; N isotope; N aggregation; Lac de gras; PERIDOTITIC DIAMONDS; PANDA KIMBERLITE; ISOTOPE; CARBON; OLIVINE; INCLUSIONS; AGGREGATION; RINGWOODITE; DIFFRACTION; EVOLUTION;
D O I
10.1007/s00710-025-00899-0
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 ; 070902 ;
摘要
We present the first study of 73 micro- and macro-diamonds and their inclusions from the Sequoia kimberlites, Central Lac de Gras kimberlite field, NWT. Nitrogen aggregation systematics show the presence of a diamond population that resided in the mantle at high temperatures (> 1250 degrees C; 17% of all Type I diamonds), plus a high proportion of Type II diamonds (26%). Raman analysis of mineral inclusions in 24 diamonds reveals that the Sequoia kimberlites sampled both lithospheric (19 diamonds) and sublithospheric (5 diamonds) mantle sources. Olivine crystals coexisting with minerals characteristic of retrogressed sublithospheric assemblages display an extreme shift in Raman peak positions, indicating high pressure of entrapment. In one diamond, we observed the typical X-ray diffraction reflections of preserved ringwoodite, indicating the coexisting olivine identified by Raman is retrogressed. The preserved ringwoodite was stable in the transition zone. Lithospheric diamonds are of peridotitic affinity and the presence of clinopyroxene inclusions indicates sampling of possibly younger, less depleted portions of the mantle beneath Lac de Gras. Eight percent of the studied diamonds are fibrous and trap mineral micro-inclusions derived from peridotitic substrates. The diamond C and N isotope compositions are generally within typical mantle values, but the delta C-13 variability significantly exceeds the mantle range to both lower and higher values. Diamond internal variations in delta C-13-delta N-15 exceeding the mantle range document the influence of subducted fluids in diamond formation. This first look at Sequoia diamonds underlines the need for exploration approaches that assess the presence of lherzolitic and sublithospheric-derived diamonds during indicator mineral assessment.
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页数:15
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