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首页> 外文期刊>Contributions to Mineralogy and Petrology >Mineral inclusions in sublithospheric diamonds from Collier 4 kimberlite pipe, Juina, Brazil: subducted protoliths, carbonated melts and primary kimberlite magmatism
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Mineral inclusions in sublithospheric diamonds from Collier 4 kimberlite pipe, Juina, Brazil: subducted protoliths, carbonated melts and primary kimberlite magmatism

机译：巴西朱纳Collier 4金伯利岩管的岩石圈以下钻石中的矿物包裹体：俯冲的原生石，碳酸盐熔体和主要金伯利岩岩浆作用

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摘要

We report on a suite of diamonds from the Cretaceous Collier 4 kimberlite pipe, Juina, Brazil, that are predominantly nitrogen-free type II crystals showing complex internal growth structures. Syngenetic mineral inclusions comprise calcium- and titanium-rich phases with perovskite stoichiometry, Ca-rich majoritic-garnet, clinopyroxene, olivine, TAPP phase, minerals with stoichiometries of CAS and K-hollandite phases, SiO2, FeO, native iron, low-Ni sulfides, and Ca–Mg-carbonate. We divide the diamonds into three groups on the basis of the carbon isotope compositions (δ13C) of diamond core zones. Group 1 diamonds have heavy, mantle-like δ13C (−5 to −10‰) with mineral inclusions indicating a transition zone origin from mafic protoliths. Group 2 diamonds have intermediate δ13C (−12 to −15‰), with inclusion compositions indicating crystallization from near-primary and differentiated carbonated melts derived from oceanic crust in the deep upper mantle or transition zone. A 206Pb/238U age of 101 ± 7 Ma on a CaTiSi-perovskite inclusion (Group 2) is close to the kimberlite emplacement time (93.1 ± 1.5 Ma). Group 3 diamonds have extremely light δ13C (−25‰), and host inclusions have compositions akin to high-pressure–temperature phases expected to be stable in pelagic sediments subducted to transition zone depths. Collectively, the Collier 4 diamonds and their inclusions indicate multi-stage, polybaric growth histories in dynamically changing chemical environments. The young inclusion age, the ubiquitous chemical and isotopic characteristics indicative of subducted materials, and the regional tectonic history, suggest a model in which generation of sublithospheric diamonds and their inclusions, and the proto-kimberlite magmas, are related genetically, temporally and geographically to the interaction of subducted lithosphere and a Cretaceous plume.
机译：我们报告了一组来自巴西Juina的白垩纪Collier 4金伯利岩管的钻石，这些钻石主要是无氮的II型晶体，显示出复杂的内部生长结构。同生矿物包裹体包括钙钛矿化学计量比的富含钙和钛的相，钙富集的石榴石，斜辉石，橄榄石，TAPP相，化学计量比为CAS和K-辉石相的矿物，SiO 2 ， FeO，天然铁，低镍硫化物和碳酸钙镁。根据金刚石核心区的碳同位素组成（δ 13 C），将金刚石分为三类。第1组钻石的地幔样δ 13 C重（-5至-10‰），矿物包裹体表明过渡带起源于镁铁质原石。第2组钻石的中间δ 13 C（-12至-15‰），夹杂物成分表明从上地幔深部或过渡带大洋壳衍生的近原始的和分化的碳酸盐熔体结晶。 CaTiSi-钙钛矿夹杂物（第2组）上的 206 Pb / 238 U年龄为101±7 Ma，接近金伯利岩放置时间（93.1±1.5 Ma）。第3组钻石的δ 13 C非常轻（−25‰），主体包裹体的成分类似于高压-高温相，预计在俯冲到过渡带深度的浮游沉积物中是稳定的。总的来说，Collier 4钻石及其包含物指示了在动态变化的化学环境中的多阶段，多变量生长历史。年轻的夹杂物年龄，指示俯冲物质的普遍化学和同位素特征以及区域构造历史，提出了一种模式，其中，岩石圈以下的钻石及其包裹体和原金伯利岩岩浆的产生与时间，地理和地理相关。俯冲岩石圈与白垩纪羽流的相互作用。

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