The nature and origin of lamprophyres: an overview
The nature and origin of lamprophyres: an overview
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DOI：
10.1144/gsl.sp.1987.030.01.09
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发表时间：
1987
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影响因子：
--
通讯作者：
N. Rock
中科院分区：
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作者：
N. Rock
Lamberres是“碱性岩石”，因为它们在给定的SiO2百分比下携带高碱，以及一种或多种标准ne，lc或ac，模态foid和富含Na-K-Ti的角闪石或辉石。全岩H_2O、CO_2、Sr、Ba含量均高于其它硅酸盐火成岩。角闪石（Ti、Ba）、钾长石（Ba、Fe 3）、金云母（Ti、Ba、Fe 3）和辉石（Ti、Al、Fe 3）中相关元素亚类的含量是自然界已知的最高值。“原始”矿物（透辉石、镁橄榄石）通常与“演化”矿物（钠长石+正长石、石英）共存。四个明确定义的“分支”的lamaburre '氏族'有独特的组成：钙碱性（钾玄石）lamaburres（minettes等），在层状矿物中，只有一种具有混合的碱-钙-碱亲和性;碱性层状矿物（camptonites等）玄武质到霞岩质，在层状岩石中，通常只有Na < K;超镁铁质层状岩石（钠长石等）是硅酸盐火成岩中最贫硅、富钙的岩石，可分级为碳酸岩、钾镁煌斑岩（奥辉岩等）富K、Rb、Ba、Th、Mg、Cr、Ni等元素，SiO2含量以安山质为主，并含有一系列特征矿物（硅镁矾等）。每个分支至少包括四种岩石类型，它们之间的相似性远大于其他分支的岩石类型;然而，某些岩石类型可以在一个分支内被分为稍微不同的“家族”（例如金云母和镁铁质钾煌斑岩）。金伯利岩可以作为Lambertre族的第五个分支。天气图和表格，根据约5000个主要的，微量元素和矿物分析，提出，以帮助识别和分类。碱性岩比一般所说的要普遍得多，在世界范围内比许多其他碱性岩和整个地质记录中出现的构造环境更多。它们可能近似地内岩浆成分。几乎所有代表原始岩浆，许多代表原生岩浆。有些代表了大范围含水碱性侵入岩套的母岩浆：钙碱性层状岩到钾质辉石岩-闪长岩-正长岩-花岗岩岩体（Cortlandt）;碱性层状岩到角闪石辉长岩-正长岩岩体（Monteregian Hills）;超镁铁质层状岩到伊久岩-碳酸岩杂岩（Fen）。
Summary Lamprophyres are ‘alkaline rocks’ because they carry high alkalis at a given percentage of SiO2, together with one or more of normative ne, lc or ac, modal foids, and Na-K-Ti-rich amphiboles or pyroxenes. They reach higher whole-rock H2O, CO2, Sr and Ba contents than other silicate igneous rocks. Contents of related element subsets in amphiboles (Ti, Ba), K-feldspars (Ba, Fe3), phlogopites (Ti, Ba, Fe3) and pyroxenes (Ti, Al, Fe3) include among the highest values known in nature for these minerals. ‘Primitive’ minerals (diopside, forsterite) commonly coexist with ‘evolved’ minerals (albite + orthoclase, quartz). Four well-defined ‘branches’ of the lamprophyre ‘clan’ have distinctive compositions: calc-alkaline (shoshonitic) lamprophyres (minettes etc.), alone among lamprophyres, have mixed alkaline-calc-alkaline affinities; alkaline lamprophyres (camptonites etc.) are basanitic to nephelinitic and, alone among lamprophyres, usually have Na < K; ultramafic lamprophyres (alnöites etc.) are the most Si poor and Ca rich of silicate igneous rocks, and grade into carbonatites; lamproites (orendites etc.) are uniquely rich in K, Rb, Ba, Th, Mg, Cr and Ni at mainly ‘andesitic’ SiO2 contents, and carry a suite of diagnostic minerals (wadeite etc.). Each branch comprises at least four rock types which resemble each other much more than rock types of other branches; however, some rock types can be grouped into slightly distinct ‘families’ within one branch (e.g. phlogopitic and madupitic lamproites). A case can be made for including kimberlites as a fifth branch of the lamprophyre clan. Synoptic plots and tables, based on some 5000 major, trace-element and mineral analyses, are presented, to aid identification and classification. Lamprophyres are far more common than generally stated, occurring worldwide in more tectonic settings than many other alkaline rocks and throughout the geological record. They may approximate intratelluric magma compositions. Nearly all represent primitive magmas, and many represent primary magmas. Some represent parental magmas to a wide range of hydrous alkaline intrusive suites: calc-alkaline lamprophyres to potassic pyroxenite-diorite-shonkinite-syenite-granite plutons (Cortlandt); alkaline lamprophyres to hornblendic gabbro-syenite plutons (Monteregian Hills); and ultramafic lamprophyres to ijolite-carbonatite complexes (Fen).