Geochemical and petrological evidence of the subduction of delaminated Adriatic continental lithosphere in the genesis of the Neogene-Quaternary magmatism of central Italy
Geochemical and petrological evidence of the subduction of delaminated Adriatic continental lithosphere in the genesis of the Neogene-Quaternary magmatism of central Italy
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DOI：
10.1016/0040-1951(93)90161-c
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发表时间：
1993-07
期刊：
影响因子：
2.9
通讯作者：
G. Serri;F. Innocenti;P. Manetti
中科院分区：
文献类型：
--
作者：
G. Serri;F. Innocenti;P. Manetti
摘要Serri，G.，Innocenti，F.和Manetti，P.，1993.意大利中部新近纪-第四纪岩浆作用成因中分层的亚得里亚大陆岩石圈俯冲的地球化学和岩石学证据。在：MJR Wortel，U.汉森和R.萨巴迪尼（编辑），地幔过程和地质过程之间的关系在或接近地球表面。Tectonophysics，223：117-147.北方亚平宁弧晚第三纪-第四纪岩浆活动在时间和空间上分为四个阶段，从西向东逐渐年轻：第一阶段，~ 14 Ma;第二阶段，7.3- 6.0Ma;第三阶段，5.1- 2.2Ma;第四阶段，1.3- 0.1Ma。这种岩浆活动是三个物理上独立的来源激活的结果：（1）亚得里亚海大陆地壳，提取的地幔在晚元古代;（2）一个强烈的耐火，最近富钾方辉橄榄岩地幔位于岩石圈的机械边界层（MBL）;和（3）最近交代，cpx丰富的地幔，成分变化从二辉橄榄岩到wehrlite-linopyroxenite，解释为一个短暂的富钾软流圈。亚得里亚海大陆地壳是托斯卡纳地区酸性深成岩和火山岩的主要来源。酸性岩浆活动主要在以吉利奥岛为中心的椭球区域（约150× 300 km）内发现，此处定义为托斯卡纳地壳穹隆。在这一区域内，迄今尚未发现未受重要地壳混染过程影响并与地壳深熔熔融物混合的幔源岩浆，纯地壳岩浆很少，但有代表性，例如圣文森佐和Ravenstrada流纹岩。几乎所有的托斯卡纳酸性中心都显示出与钾质幔源岩浆混合的证据。原始岩石（Mg#> 65）的主量和微量元素以及87 Sr、86 Sr和143 Nd、144 Nd数据表明，岩浆为两组幔源岩浆。这些定义了两个不同的地幔富集趋势，这两个基本上是由于增加了丰富的K组分交代分离，成分多样，上地幔部门。在这两种情况下，这些富集过程最显着的矿物学效应是通过流体和/或熔体与地幔之间的反应产生不同量的金云母。第一组的岩石（ol-hy和Q-标准，钾镁煌斑岩，超钾质高镁红土，超钾质钾玄岩和钾玄岩：饱和趋势）被认为是在低压（< 50公里）下强烈的部分熔融所产生的。（钾镁煌斑岩）到适度贫化的金云母方辉橄榄岩来源，高87 Sr/86 Sr比值的贫钙锶熔体（> 0.717），Ce/Sr（> 0.3）和K2 O-Na 2 O（> 6-7），143 Nd-144 Nd比值低（~ 0.5121-0.5120）和Ba/La（< 20）比值，推测该组分是由上地壳储集层中俯冲的无碳酸盐物质（如非锐钛矿长英质麻粒岩）部分熔融形成的。这种物质在地中海中部地区非常常见，要么是花岗岩类侵入岩/陆源沉积物，要么是变质沉积岩，非restitic下地壳。第二组原始岩为临界欠饱和，主要为白榴石、闪辉白榴石、白榴石碧玄岩、黄长岩（欠饱和趋势）。实验岩石学表明，这些岩石的部分熔融形成的富镁金云母，单斜辉石丰富的地幔在较高的压力比第一组原始岩浆。微量元素模拟结果表明，第二类地幔源区的成因主要有三个组成部分：（a）典型的MORB-OIB型地幔;（B）地幔源区的形成机制。
Abstract Serri, G., Innocenti, F. and Manetti, P., 1993. Geochemical and petrological evidence of the subduction of delaminated Adriatic continental lithosphere in the genesis of the Neogene-Quaternary magmatism of central Italy. In: MJR Wortel, U. Hansen and R. Sabadini (Editors), Relationships between Mantle Processes and Geological Processes at or near The Earth's Surface. Tectonophysics, 223: 117–147. The Neogene-Quaternary magmatism of the northern Apenninic arc took place in four phases separated in space and time which become progressively younger from west to east: Phase I,~ 14 Ma; Phase II, 7.3-6.0 Ma; Phase III, 5.1-2.2 Ma; Phase IV, 1.3-0.1 Ma. This magmatism is the result of the activation of three physically separate sources:(1) the Adriatic continental crust, extracted from the mantle in the late Proterozoic;(2) a strongly refractory, recently K-enriched harzburgitic mantle located in the mechanical boundary layer (MBL) of the lithosphere; and (3) a recently metasomatized, cpx-rich mantle, compositionally variable from Iherzolite to wehrlite-clinopyroxenite, interpreted as an ephemerally K-enriched asthenosphere. The Adriatic continental crust is the dominant source of the acid plutonic and volcanic rocks of the Tuscan region. The acid magmatism is mostly found inside an ellipsoidal area (about 150× 300 km) centred on Giglio Island, here defined as the Tuscan Crustal Dome. Within this area, mantle-derived magmas unaffected by important crustal contamination processes and mixing with crustal anatectic melts have so far not been found. Pure crustal magmas are rare but are represented, for example by some of the San Vincenzo and Roccastrada rhyolites. Virtually all the Tuscan acid centres show evidence of mixing with potassic mantle-derived magmas. Major and trace elements, as well as 87 Sr 86 Sr and 143 Nd 144 Nd data, on primitive rocks (Mg#> 65) reveal two groups of mantle-derived magmas. These define two distinct mantle enrichment trends, both essentially due to the additions of K-rich components which metasomatized separate, compositionally diverse, upper mantle sectors. In both cases the most remarkable mineralogical effect of these enrichment processes is the production of variable amount of phlogopite through reaction between fluids and/or melts with the mantle. The rocks of group I (ol-hy and Q-normative, lamproites, ultrapotassic high-Mg latites, ultrapotassic shoshonites and shoshonites: saturated trend) are considered to be derived by partial melting at low pressure (< 50 km) of strongly (lamproites) to moderately depleted phlogopite harzburgitic sources produced by reaction of residual peridotites with a K-Si-rich, Ca-Sr-poor melt with high ratios of 87 Sr 86 Sr (> 0.717), Ce/Sr (> 0.3) and K 2 O Na 2 O (> 6–7), and low ratios of 143 Nd 144 Nd (~ 0.5121-0.5120) and Ba/La (< 20) ratios; it is proposed that this component was formed by partial melting of subducted carbonate-free material of the upper crustal reservoir (eg, non-restitic felsic granulites). This material is very common in the central Mediterranean region either as granitoid plutons/terrigenous sediments or as metasedimentary, non-restitic lower crust. The primitive rocks of group II are critically undersaturated, mostly leucitites, tephritic leucitites, leucite basanites, melilitites (undersaturated trend). Experimental petrology suggests that these rocks were formed by partial melting of a variably enriched phlogopite, clinopyroxene-rich mantle at higher pressure than group I primitive magmas. Trace-element modelling indicates that three components were involved in the genesis of group II mantle source:(a) a typical MORB-OIB-like mantle;(b) a …