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Role of Liquid Immiscibility in the Formation of the Rare Metal Granites of the Katugin Massif, Aldan Shield 液体不溶性在阿尔丹地盾卡图金地块稀有金属花岗岩形成过程中的作用
IF 1 4区 地球科学 Q3 GEOCHEMISTRY & GEOPHYSICS Pub Date : 2024-07-15 DOI: 10.1134/S0869591124700127
E. V. Tolmacheva, S. D. Velikoslavinskii, A. B. Kotov, A. M. Larin, E. V. Sklyarov, D. P. Gladkochub, T. V. Donskaya, T. M. Skovitina, V. P. Kovach, O. L. Galankina

The paper discusses possible immiscibility between fluoride salt (“cryolite”) and silicate liquids into which the parental melt of the Katugin massif exsolves, and the petrological implications of this phenomenon. Results of a detailed study of the cryolite and zircon are presented. Liquid immiscibility is demonstrated to have triggered the massive crystallization of zircon and, together with the processes of subsequent evolution of the cryolite melt, contributed to the formation of the large cryolite bodies. Data on mineral-hosted inclusions were used to estimate the crystallization temperatures of fluoride salt and silicate melts and outline the pathways of their evolution during the formation of the massif. It is shown that the granites of the Katugin and West Katugin massifs were most likely derived from distinct sources, that differed mainly in fluorine content. Data on the chemical composition of three zircon generations identified in the granites of the Katugin massif are presented.

论文讨论了卡图金山地块母熔体溶入的氟化盐("冰晶石")和硅酸盐液体之间可能存在的不溶性,以及这一现象对岩石学的影响。本文介绍了对冰晶石和锆石的详细研究结果。结果表明,液体的不溶性引发了锆石的大量结晶,并与冰晶石熔体的后续演化过程一起,促成了大型冰晶石体的形成。有关矿物包裹体的数据被用来估算氟化盐和硅酸盐熔体的结晶温度,并勾勒出它们在地块形成过程中的演化路径。研究表明,卡图金山和西卡图金山丘的花岗岩很可能来自不同的矿源,它们主要在氟含量上存在差异。本文介绍了在卡图金山地块花岗岩中发现的三代锆石的化学成分数据。
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引用次数: 0
Properties of Fluids during Metasomatic Alteration of Metamorphic Rocks under P–T Conditions of the Middle Crust: An Example from the Bolshie Keivy Region, Belomorian–Lapland Orogen, Fennoscandian Shield 中地壳 P-T 条件下变质岩变质蜕变过程中流体的性质:以芬诺斯堪地盾贝洛莫利亚-拉普兰造山带博尔希-凯维地区为例
IF 1 4区 地球科学 Q3 GEOCHEMISTRY & GEOPHYSICS Pub Date : 2024-07-15 DOI: 10.1134/S0869591124700097
S. A. Bushmin, Y. A. Vapnik, M. V. Ivanov, A. B. Kol’tsov, Y. M. Lebedeva, O. V. Aleksandrovich, E. V. Savva

Properties of fluids under P–T conditions of the middle crust were studied with reference to the metasomatic alteration of metamorphic rocks (amphibolite facies) of the Bolshie Keivy nappe of the Keivy terrane of the Belomorian–Lapland collision orogen of the Fennoscandian shield. Properties of the fluids were studied in five selected types of rocks: metamorphic schists and gneisses with graphite, metasomatic quartz rocks with a high content of graphite, kyanite–quartz veins with wall-rock metasomatites, and metasomatic quartz-bearing kyanite rocks and anchimonomineral quartz veins. NaCl, CaCl2, CO2, N2, CH4, heavier hydrocarbons, and graphite were identified in the fluid inclusions using microthermometry and Raman spectroscopy. Using the method of multiequilibrium thermobarometry for mineral associations and the density of CO2 inclusions, a retrograde P–T path was calculated, which reflects the P–T exhumation history of the rocks. An explanation was proposed for the presence of water inclusions with NaCl of low salinity among inclusions of high salinity with NaCl and CaCl2. Comparison of data on the H2O activity (inferred from mineral equilibria) and salt content (data on fluid inclusions) with those of a model fluid (thermodynamic model of the H2O–NaCl–CaCl2–CO2 system) showed a good agreement between natural and model data. Natural and model data were synthesized to analyze variations in the phase state and chemical composition, fluid properties, including H2O activity, density, and salinity along the retrograde P–T trend.

研究了中地壳 P-T 条件下的流体性质,并参考了芬诺斯康地盾贝洛莫利亚-拉普兰碰撞造山带基维地层博尔希基维岩脉变质岩(闪长岩面)的变质蚀变情况。在五种选定的岩石中研究了流体的性质:含石墨的变质片岩和片麻岩、石墨含量高的变质石英岩、含壁岩变质岩的辉绿岩-石英脉、含辉绿岩的变质石英岩和锚定矿物石英脉。利用微测温和拉曼光谱鉴定了流体包裹体中的 NaCl、CaCl2、CO2、N2、CH4、较重的碳氢化合物和石墨。利用矿物关联的多平衡热压法和二氧化碳包裹体的密度,计算出了一条逆行的 P-T 路径,反映了岩石的 P-T 排泄史。提出了在高盐度的氯化钠和氯化钙包裹体中存在低盐度氯化钠水包裹体的解释。将 H2O 活性数据(根据矿物平衡推断)和盐含量数据(流体包裹体数据)与模型流体数据(H2O-NaCl-CaCl2-CO2 系统热力学模型)进行比较后发现,天然数据与模型数据非常一致。综合自然数据和模型数据,分析了沿逆行 P-T 变化趋势的相态和化学成分、流体性质(包括 H2O 活性、密度和盐度)的变化。
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引用次数: 0
Metamorphosed Ultramafic and Mafic Lithoclasts and Detrital Minerals from Sandstones of Clastic Ophiolitic Deposits of the Rassokha Terrane: A Setting of Formation of the Chersky Range Ophiolites 拉索卡地层碎屑蛇绿岩沉积砂岩中变质的超基性和镁基性岩屑和碎屑矿物:切尔斯基山脉蛇绿岩的形成背景
IF 1 4区 地球科学 Q3 GEOCHEMISTRY & GEOPHYSICS Pub Date : 2024-05-27 DOI: 10.1134/S0869591124700048
G. V. Ledneva, B. A. Bazylev, S. N. Sychev, A. V. Rogov

Ophiolite-derived clastic rocks of the Rassokha terrane in the Chersky Range of the Verkhoyansk−Kolyma folded area were studied to obtain representative characteristics of the eroded source metamorphosed ultramafic and mafic rocks, to gain an insight into the possible geodynamic setting in which the protoliths of these rocks were formed, and to identify the possible source of the eroded material. The composition of lithoclasts and detrital minerals of the serpentinite and listwanite sandstones suggests that their source was composed of serpentinite, chloritite, listwanite, and dolomite rocks and that this source was proximal. Prior to the source erosion, the ultramafic and mafic rocks were metamorphosed and recrystallized, listwanite was formed, and the ultramafic rocks were tectonically disintegrated and combined with units of carbonate rocks (dolomite). Ultramafic rocks from lithoclasts experienced allochemical metamorphic retrogression during at least the latest stage of their serpentinization in a nonoceanic setting, where also the listwanite was formed. The Late Neoproterozoic ophiolites of the collisional belt of the Chersky Range were the most probable source for the protoliths of the clastic material. The protoliths of the ophiolite rock were probably formed in a backarc setting. Considered together with the published ages, our data indicate that relics of suprasubduction oceanic lithosphere of the Neoproterozoic basin occurred in the Chersky Range.

摘要 对上霍扬斯克-科雷马褶皱区切尔斯基山脉拉索卡岩系的蛇绿岩衍生碎屑岩进行了研究,以获得侵蚀源变质超基性岩和黑云母岩的代表性特征,深入了解这些岩石原岩形成的可能地球动力环境,并确定侵蚀物质的可能来源。蛇纹石砂岩和鳞片砂岩的岩石碎屑和碎屑矿物成分表明,它们的来源是由蛇纹石、绿泥石、鳞片砂岩和白云石岩石组成的,而且这个来源很近。在岩源侵蚀之前,超基性岩和黑云母岩经过变质和重结晶,形成了鳞片皖石,超基性岩经过构造解体,与碳酸盐岩(白云岩)单元结合在一起。来自碎屑岩的超基性岩至少在其蛇绿岩化的最近阶段经历了分配化学变质逆退,在非大洋环境中也形成了鳞片岩。切尔斯基山脉碰撞带的新近纪晚期蛇绿岩是碎屑物质原岩的最可能来源。蛇绿岩的原岩很可能是在弧后环境中形成的。结合已公布的年龄,我们的数据表明新近纪盆地的超俯冲洋岩石圈遗迹出现在切尔斯基山脉。
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引用次数: 0
Associations and Formation Conditions of a Body of Melilite Leucite Clinopyroxenite (Purtovino, Vologda Oblast, Russia): an Alkaline–Ultrabasic Paralava 俄罗斯沃洛格达州普尔托维诺)美徕石褐铁矿体的关联和形成条件:碱性-超基性副熔岩
IF 1 4区 地球科学 Q3 GEOCHEMISTRY & GEOPHYSICS Pub Date : 2024-05-27 DOI: 10.1134/S0869591124700073
A. Y. Barkov, A. A. Nikiforov, R. F. Martin, V. N. Korolyuk, S. A. Silyanov, B. M. Lobastov

A novel petrogenetic scheme is discussed for the formation of a melilite leucite clinopyroxenite body from an alkaline–ultrabasic paralava in the Purtovino area. Its protolith was likely a mixture of Upper Permian sedimentary rocks (aleurolite, marl, among others). Degassing, evaporation, and thermal (contact) metamorphism have significantly influenced the petrogenesis to produce a wide diversity of species present in mineral associations. The crystallization of paralava in a shallow setting was accompanied by an intense degassing and vesiculation of the melt, causing locally high porosity in the rock. An elevated degree of oxidation of the initial melt and progressive rise of fO2 were likely related to the H2 loss during the vesiculation and dissociation of H2O. Consequently, ferrian magnesiochromite (Mchr) and chromian spinel (Fe3+-enriched) were the early phases to crystallize; they were followed by members of the magnesioferrite–magnetite series. In situ melting of quartz-bearing and carbonate–clay rocks led to the development of domains of peralkaline felsic glass that surround partially resorbed quartz grains. Numerous grains of wollastonite and rare larnite formed during contact pyrometamorphism. The alkalis increased progressively during crystallization, with a notable enrichment in Na (up to 0.30 apfu) in the åkermanite–gehlenite series. The formation of leucite following melilite is indicated. Euhedral grains of Cpx display concentric cryptic zonation, with a zone of extreme Mg enrichment due to a local deficit in Fe2+. As consequences of the continuing rise in fO2, esseneite crystallized in the rim of zoned clinopyroxene. Two schemes of coupled substitution account for the composition of Cpx grains analyzed in various textural relationships: Mg2+ + Si4+ → (Fe3+ + Al3+) and (Ti4+ + Al3+) + (Na + K)+ → 2Mg2+ + Si4+. The pre-existing grains of olivine (associated with Mchr) were likely replaced completely by sepiolite–palygorskite associated with brownmillerite and its probable Fe3+-dominant counterpart, srebrodolskite. The investigated layer of alkaline microclinopyroxenite is unique in the Russian Plate, and a search is thus required to recognize other pyrogenic products. Also, further research is required to evaluate the contents and volumes of coal (or other sources of hydrocarbons) that could cause spontaneous and long-lasting combustion to form the considerable volume of paralava recognized in the Purtovino area.

本文讨论了从普尔托维诺地区的碱性-超基性副熔岩中形成美拉特白云石clinopyroxenite岩体的一种新的岩石学方案。其原岩很可能是上二叠统沉积岩(白云石、泥灰岩等)的混合物。脱气、蒸发和热(接触)变质作用对岩石成因产生了重大影响,从而产生了多种多样的矿物组合。帕拉瓦岩在浅层环境中结晶时,伴随着强烈的脱气和熔体的气泡化,导致岩石局部孔隙率较高。初始熔体的氧化程度升高和 fO2 的逐步上升可能与气泡过程中 H2 的损失和 H2O 的解离有关。因此,铁性菱镁铬铁矿(Mchr)和铬尖晶石(富含 Fe3+)是较早出现的结晶相;随后出现的是菱镁铁-磁铁矿系列。含石英岩和碳酸盐粘土岩的原位熔化导致了围着部分被吸收的石英颗粒的碱性长石玻璃域的形成。在接触热变质过程中,形成了大量硅灰石和稀有的拉氏石晶粒。在结晶过程中,碱性物质逐渐增加,在芒硝-绿帘石系列中,Na的含量明显增加(高达0.30apfu)。这表明白云母是在黑云母之后形成的。Cpx的八面体晶粒显示出同心的隐伏分带,由于局部的Fe2+缺乏,导致Mg极度富集区。由于 fO2 的持续上升,霰石在带状clinopyxene 的边缘结晶。两种耦合置换方案解释了在不同质地关系中分析的霞石晶粒的组成:Mg2+ + Si4+ → (Fe3+ + Al3+) 和 (Ti4+ + Al3+) + (Na + K)+ → 2Mg2+ + Si4+。先前存在的橄榄石(与 Mchr 有关)晶粒很可能完全被与褐铁矿有关的霞石-辉绿岩及其可能以 Fe3+ 为主的对应物--褐铁矿所取代。所调查的碱性微闪长岩层在俄罗斯板块中是独一无二的,因此需要寻找其他热成产物。此外,还需要进行进一步研究,以评估煤炭(或其他碳氢化合物来源)的含量和体积,这些物质可能会导致自燃和持久燃烧,从而形成在普尔托维诺地区发现的大量副熔岩。
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引用次数: 0
Age and Origin of the Subalkaline Magmatic Series of the Khibiny–Lovozero Complex 奇宾尼-洛沃泽罗复合体亚碱性岩浆系列的年龄和起源
IF 1 4区 地球科学 Q3 GEOCHEMISTRY & GEOPHYSICS Pub Date : 2024-05-27 DOI: 10.1134/S0869591124700024
A. A. Arzamastsev, A. A. Ivanova, E. B. Salnikova, A. B. Kotov, V. P. Kovach, M. V. Stifeeva, N. Yu. Zagornaya, Yu. V. Plotkina, E. V. Tolmacheva

The paper presents data on the miaskite syenites of the Lovozero massif, pulaskites of the Khibiny massif, rocks of the larvikite–lardalite series of the Kurga massif, and subalkaline volcanics, which are preserved as remnants in the roof of the massifs. The studied rocks are characterized by a low agpaitic coefficient of <1, the absence of minerals typical of peralkaline rocks (eudialyte, aenigmatite, etc.), and the presence of zircon. The morphological features and chemical composition of zircon from miaskite of the Lovozero massif syenite indicate that the mineral is of magmatic nature. The crystallization age of the miaskites was dated on zircon at 373 ± 5 Мa. The isotope-geochemical characteristics of rocks of the subalkaline series indicate that the miaskites of the Lovozero massif are of mantle origin, show no indications of their crustal contamination, and were produced during the evolution of ankaramite melt. The pulaskites of the Khibiny massif were formed according to an analogous scenario, except their assimilation with crustal material, whose proportion did not exceed, according to model calculations, 10%.

摘要 本文介绍了有关洛沃泽罗山丘的miaskite正长岩、基比尼山丘的pulaskite、库尔加山丘的拉长岩-钠长岩系列岩石以及山顶残留的亚碱性火山岩的数据。所研究的岩石的特点是躁石系数低(1),不含典型的围碱性岩石矿物(乌云母、辉绿岩等),但含有锆石。从洛沃泽罗丘陵正长岩的miaskite中提取的锆石的形态特征和化学成分表明,该矿物具有岩浆性质。锆石的结晶年代为 373 ± 5 Мa。亚碱性系列岩石的同位素地球化学特征表明,洛沃泽罗地块的miaskites源于地幔,没有地壳污染的迹象,是在安卡拉岩熔体演化过程中产生的。基比尼山丘的浆绢云母也是按照类似的情况形成的,只是与地壳物质同化,根据模型计算,其比例不超过 10%。
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引用次数: 0
Malyi Zadoi Peridotite−Gabbronorite Massif: Computational Modeling of Crystallization and Evaluation of Indicator Geochemical Parameters of the Parental Melt 马利扎多伊橄榄岩-辉绿岩地块:结晶计算模型和母体熔体地球化学指标参数评估
IF 1 4区 地球科学 Q3 GEOCHEMISTRY & GEOPHYSICS Pub Date : 2024-05-27 DOI: 10.1134/S0869591124700036
A. V. Lavrenchuk, D. P. Gladkochub, O. M. Turkina, A. S. Mekhonoshin, Ya. Yu. Shelepov

Model calculations were used to estimate the compositions of melts during fractional crystallization corresponding to the formation of the Malyi Zadoi massif, which is located in the Irkut block of the Sharyzhalgai uplift in the southwest of the Siberian craton. It is shown that the gabbronorites of the massif are comagmatic to the plagioperidotites and olivine gabbronorites. The estimates obtained for the composition of the model melts are used to characterize the composition of the mantle source of the parental melt. The geochemical characteristics led us to suggest that the parental melt of the Malyi Zadoi massif was formed by melting an enriched source, a conclusion consistent with isotope data that indicate that the mantle Sm/Nd ratio decreased in the Archean. The probable source of the parental melt could consist of depleted lithospheric mantle material metasomatized by felsic melts coming from rocks of a subducting oceanic plate.

摘要 通过模型计算,估算了与位于西伯利亚克拉通西南部 Sharyzhalgai 隆起的伊尔库特区块的 Malyi Zadoi 地块形成相应的碎裂结晶过程中的熔体成分。研究表明,该地块的榴辉岩与斜长角闪岩和橄榄石榴辉岩是共生的。根据对模型熔体成分的估计,可以确定母体熔体的地幔源成分。地球化学特征使我们认为,Malyi Zadoi 地块的母体熔体是由富集源熔化形成的,这一结论与同位素数据相一致,同位素数据表明地幔 Sm/Nd 比率在奥歇纪有所下降。母体熔体的可能来源可能是贫化的岩石圈地幔物质,由来自俯冲大洋板块岩石的长岩熔体变质而成。
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引用次数: 0
Petrogenesis of the Neoproterozoic Peraluminous Orogenic Granite and Tertiary Phonolites from Jabal Fezzan in Southern Libya 利比亚南部 Jabal Fezzan 新新生代白铝造山花岗岩和第三纪辉绿岩的岩石成因
IF 1 4区 地球科学 Q3 GEOCHEMISTRY & GEOPHYSICS Pub Date : 2024-05-27 DOI: 10.1134/S0869591124700012
Ali S. Bensera

The majority of Neoproterozoic rocks exposed in southern Libya, are comprised of intrusive coarse-grained porphyritic, two-mica, and high K-calc alkaline granite. The Jabal Fezzan Granite (JFG) is located in southwestern Libya. In this study, trace elements and whole-rock geochemistry have been used to understand the origin and the process of petrogenesis of the studied granites. The JFG is high-Si, Rb, Y, Nb, and (ASI values greater than 1.1). Mineralogically, it is characterized by the presence of minor muscovite and biotite and a lack of hornblende, exhibiting features of S-type granites, and having a character that belongs to an alkali-calcic series. According to geochemical value, light REE-enriched, characterized by moderate enrichments in LREE (La/Sm), HREE, and weak negative Eu-anomalies. The geochemical modeling of the (JFG) reveals that the JFG derived from the melting of the crust and underwent high fractional crystallization (~50%) of plagioclase and K-feldspar at (H-P) conditions (750–980°C/1–4 GPa). The Jabal Fezzan (JFG) formed during Pan-African orogenic events during the destabilization of the interior Saharan metacraton due to compression stress and transpressive movements along pre-existing weakness and reactivation of shear zones inherited from Paleoproterozoic evolution. The Neoproterozoic basement forms the northernmost margin of the intracratonic Muruzq Basin, as evidenced by (greenschist facies) and intruded granitic rocks derived at the syn-collision stage (630–540 Ma).

摘要利比亚南部出露的新新生代岩石大多由侵入性粗粒斑岩、双云母和高钾钙碱性花岗岩组成。Jabal Fezzan 花岗岩(JFG)位于利比亚西南部。本研究采用微量元素和全岩地球化学方法来了解所研究花岗岩的成因和岩石成因过程。JFG 属于高硅、高铷、高钇、高铌和(ASI 值大于 1.1)花岗岩。在矿物学上,它的特征是含有少量的黝帘石和斜长石,缺乏角闪石,表现出 S 型花岗岩的特征,具有属于碱钙质系列的特征。根据地球化学值,富含轻度 REE,其特征是 LREE(La/Sm)、HREE 中度富集,Eu 负异常较弱。JFG的地球化学模型显示,JFG源于地壳熔融,在(H-P)条件下(750-980°C/1-4 GPa)经历了斜长石和K长石的高分化结晶(约50%)。Jabal Fezzan(JFG)是在泛非造山运动中形成的,当时撒哈拉内部的元古宙由于压缩应力和沿原已存在的薄弱剪切带的转位运动以及古新生代演化过程中遗留下来的剪切带的重新激活而导致内部不稳定。新元古代基底构成了地壳内穆鲁兹克盆地的最北缘,其证据是在同步碰撞阶段(630-540Ma)衍生的(绿泥石面)和侵入花岗岩石。
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引用次数: 0
Rocks of the Ary-Bulak Ongonite Massif: Relationship between Geochemical Features, Mineral-Phase Assemblages, and Formation Processes 阿利-布拉克翁贡岩地块的岩石:地球化学特征、矿物相组合与形成过程之间的关系
IF 1 4区 地球科学 Q3 GEOCHEMISTRY & GEOPHYSICS Pub Date : 2024-05-27 DOI: 10.1134/S0869591124700061
I. S. Peretyazhko, E. A. Savina, A. S. Dmitrieva

The paper reports the study of geochemistry, mineral-phase assemblages of rocks of the Ary-Bulak ongonite massif, compositions of major, minor and accessory minerals (quartz, feldspars, topaz, zinnwaldite, prosopite, rare Ca–Al-fluorides, W-ixiolite, columbite, zircon, cassiterite, and fluocerite), fluoride–calcium (F–Ca) phase, and fluorite formed from it. The rock-forming minerals of porphyritic ongonites are quartz, albite and sanidine, and minor minerals are topaz and zinnwaldite. The ongonitic matrix is composed of a quartz–sanidine–albite assemblage with micron-sized needle-shaped topaz crystals. In transitional porphyritic rocks and in the endocontact aphyric zone, the interstices between matrix minerals are filled with a F–Ca phase formed from a F–Ca (fluoritic) stoichiometric melt. Fluoride–silicate liquid immiscibility in ongonitic magma and fluid-magmatic processes led to the redistribution of REE, Y, and many trace elements between melts, fluids, minerals and a contrasting change in mineral-phase assemblages in the rocks. This is associated with the appearance of M-type (T1 La–Nd, T4 Er–Lu) and W-type (T3 Gd–Ho) tetrad effects in the chondrite-normalized REE patterns of rocks. Degassing of magmatic fluids through the endocontact aphyric zone was accompanied by the crystallization of Sr-bearing prosopite and hydrous Ca–Al-fluorides. Aphyric rocks, compared to porphyritic ongonites and porphyritic transitional rocks, are enriched in H2O, Sr, Ba, Rb, Sn, W, Ta, Be, Zr, Hf, Sb, As, Sc, but contain less Li, Pb, Zn, Y and REE. During the effect of magmatic fluids on rocks enriched in Ca and F, especially in the endocontact aphyric zone, albite was partially or completely replaced by the F–Ca phase and kaolinite, and the F–Ca phase recrystallized into aggregates of micron-sized grains of stoichiometric fluorite without trace elements. Rb-Cs mica also crystallized in the rim of zinnwaldite laths, the zones of which maximally enriched in rubidium with the cation relation Rb > K > Cs may be a new mineral. The geochemistry of the rocks, the features of their mineral-phase assemblages, the compositional evolution of the minerals and the F–Ca phase are a consequence of the formation of the Ary-Bulak massif from ongonitic magma during a fluid-magmatic process complicated by fluoride–silicate liquid immiscibility with the participation of fluoritic and other fluoride melts, as well as magmatic fluids of P–Q and the first types.

本文报告了对阿利-布拉克缟玛瑙岩群岩石的地球化学、矿物相组合、主要矿物、次要矿物和附属矿物(石英、长石、黄玉、黝帘石、黝帘石、稀有钙铝氟化物、W-黝帘石、铌铁矿、锆石、锡石和萤石)的成分、氟钙(F-Ca)相以及由其形成的萤石的研究。斑状缟玛瑙岩的成岩矿物为石英、白云石和辉绿岩,次要矿物为黄玉和黝帘石。缟玛瑙基质由石英-闪锌矿-白云石集合体组成,其中有微米大小的针状黄玉晶体。在过渡斑岩和内接触斑岩区,基质矿物之间的间隙由 F-Ca(萤石质)化学熔体形成的 F-Ca 相填充。缟玛瑙岩浆中氟硅酸盐液体的不溶性和流体-岩浆过程导致了 REE、Y 和许多微量元素在熔体、流体、矿物之间的重新分布,以及岩石中矿物相组合的对比变化。这与岩石的软玉归一化REE模式中出现的M型(T1 La-Nd、T4 Er-Lu)和W型(T3 Gd-Ho)四元效应有关。岩浆流体通过内接触斑岩带时,伴随着含Sr的闪长岩和含水Ca-Al-氟化物的结晶。与斑状缟玛瑙岩和斑状过渡岩相比,斑岩富含H2O、Sr、Ba、Rb、Sn、W、Ta、Be、Zr、Hf、Sb、As、Sc,但Li、Pb、Zn、Y和REE含量较少。在岩浆流体对富含Ca和F的岩石的作用过程中,特别是在内生接触斑岩带,白云母部分或全部被F-Ca相和高岭石所取代,F-Ca相重结晶为不含微量元素的微米级计量萤石颗粒集合体。Rb-Cs 云母也结晶于黝帘石板条的边缘,其中铷含量最高的区域与阳离子关系为 Rb > K > Cs,可能是一种新矿物。岩石的地球化学性质、矿物相组合特征、矿物成分演变以及 F-Ca 相,都是阿利-布拉克岩块由翁贡岩岩浆在流体-岩浆过程中形成的结果,该过程因氟化物-硅酸盐液体不溶性而复杂,萤石熔体和其他氟化物熔体以及 P-Q 和第一类岩浆流体也参与其中。
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引用次数: 0
Fenner Trend and the Role of Fractional Crystallization and Ferrobasaltic Magma Immiscibility in Granophyre Petrogenesis: the Case of the Mesoproterozoic Valaam Sill in the Ladoga Graben, Karelia 芬纳趋势以及碎屑结晶和铁基性岩浆不溶性在花岗岩成岩过程中的作用:卡累利阿拉多加地块中新生代瓦拉岩山的案例
IF 1 4区 地球科学 Q3 GEOCHEMISTRY & GEOPHYSICS Pub Date : 2024-05-27 DOI: 10.1134/S086959112470005X
A. A. Nosova, N. M. Lebedeva, A. A. Vozniak, L. V. Sazonova, I. A. Kondrashov, Y. O. Larionova, E. V. Kovalchuk

This paper presents the results of petrographical, mineralogical, geochemical, and isotope-geochemical studies of granophyres and host ferrogabbros, quartz ferromonzogabbros, quartz monzodiorites, and quartz monzonites in the Mesoproterozoic Valaam sill in the Ladoga Graben on the Karelian Craton. The sill is poorly layered: the ferrogabbros compose the lower part of the sill, the middle part consists of quartz gabbro-monzonites and quartz monzonites, while graphic leucogranites (granophyres) form a dense network of veins mainly in the upper part of the sill. Geochemical features of ferrogabbro, iron-rich composition of olivine and pyroxene, and low Ca composition of plagioclase indicate the evolution along the Fenner trend. The granophyres have petro- and geochemical characteristics of anorogenic alkaline granites, with negative Eu/Eu* = 0.15–0.49 and REE distribution patterns similar to those of granophyres of layered intrusions. All rocks of the sill have close Sr isotopic composition (87Sr/86Sr)T = 0.7043–0.7066, and εNd values ranging from −9.6 to −11.2. Model calculations show that fractional crystallization can lead the initial ferrogabbro melt into the immiscibility field. Ilmenite–magnetite–silicate microstructures have been identified in the ferrogabbro and ferromontzogabbro from the sill; similar microstructures in layered intrusions are considered as evidence for the immiscibility of Fe-rich and Si-rich liquids (Holness et al., 2011; Dong et al., 2013). The segregation of the high-silica melt may have occurred in an intermediate crustal chamber at around 350 MPa and 960oC; magma was supplied as crystalline mush at the sill emplacement level at around 70 MPa and acidic melt migrated through it. This melt underwent fractional crystallization and interacted with host minerals. At the level of sill emplacement, it crystallized under supercooling into granophyre aggregates. The example of the Valaam sill shows that when the Fenner fractionation reaches the final composition–-ferrogabbro, its further evolution with a conjugate decrease in SiO2 and Fe contents can be related to the incomplete separation and mixing of Fe-rich melts and immiscibly split felsic melt. Such a mechanism can be implemented for the formation of the mafic part of AMCG-type massifs.

本文介绍了对卡累利阿克拉通拉多加地块中新生代瓦拉姆岩体中的花岗岩和寄主铁闪长岩、石英铁闪长岩、石英闪长岩和石英单长岩进行岩相学、矿物学、地球化学和同位素地球化学研究的结果。岩体的层理较差:铁闪长岩构成了岩体的下部,中部由石英辉长岩-单长岩和石英单长岩组成,而图形白云岩(花岗闪长岩)则主要在岩体的上部形成了密集的矿脉网络。铁闪长岩的地球化学特征、橄榄石和辉石的富铁成分以及斜长石的低钙成分显示了沿 Fenner 走向的演化过程。花岗岩具有成岩碱性花岗岩的岩石学和地球化学特征,负Eu/Eu* = 0.15-0.49,REE分布模式与层状侵入体的花岗岩相似。山体所有岩石的Sr同位素组成(87Sr/86Sr)T = 0.7043-0.7066,εNd值介于-9.6至-11.2之间。模型计算表明,部分结晶可将最初的铁闪长岩熔体带入不熔场。在来自山体的铁闪长岩和铁锰闪长岩中发现了钛铁矿-磁铁矿-硅酸盐微结构;层状侵入体中的类似微结构被认为是富铁液和富硅液不溶性的证据(Holness等人,2011年;Dong等人,2013年)。高硅熔体的偏析可能发生在 350 兆帕和 960 摄氏度左右的中间地壳室中;岩浆以结晶浆的形式供应到 70 兆帕左右的山体喷出层,酸性熔体通过它迁移。这种熔体经历了碎裂结晶,并与寄主矿物相互作用。在山体隆起层面,它在过冷作用下结晶成粒状集合体。瓦拉姆山体的例子表明,当芬纳分馏达到最终成分--铁闪长岩时,其进一步演变与二氧化硅和铁含量的共轭减少可能与富铁熔体和不熔融长熔体的不完全分离和混合有关。这种机制可用于形成AMCG型地块的岩浆部分。
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引用次数: 0
Model of the Formation of Monzogabbrodiorite–Syenite–Granitoid Intrusions by the Example of the Akzhailau Massif (Eastern Kazakhstan) 以阿克扎伊劳地块(哈萨克斯坦东部)为例的蒙左闪长岩-闪长岩-花岗岩侵入体形成模型
IF 1 4区 地球科学 Q3 GEOCHEMISTRY & GEOPHYSICS Pub Date : 2024-04-22 DOI: 10.1134/S086959112402005X
P. D. Kotler, S. V. Khromykh, A. V. Zakharova, D. V. Semenova, A. V. Kulikova, A. G. Badretdinov, E. I. Mikheev, A. S. Volosov

This paper presents a model of the formation of a multiphase Akzhailau granitoid massif formed within a Caledonian block of the Earth’s crust in the Hercynian time. This work is based on the results of major and trace element composition, geochronological, mineralogical and isotope-geochemical studies. Three stages of the formation of the Akzhailau massif are distinguished, which differ significantly from the previously accepted concepts about the multicomplex and polychronous origin of this intrusion: (1) the formation of moderately alkaline A2-type leuсogranites (308–301 Ma); (2) intrusion of monzodiorites into the base of leucogranites (~295 Ma), increasing degree of partial melting of protoliths with the formation of syenites and moderately alkaline granites of I-type (294–292 Ma); (3) intrusion of dikes and small bodies of alkaline ferroeckermannite A1-type leucogranites in the west and north of massif (~289 Ma). The Akzhailau massif was formed within about 15 Myr in the middle–upper crust through the interaction of plume-related subalkaline basitic magmas with metamorphosed crustal protolith of the orogenic structure.

本文介绍了在海西时代地壳喀里多尼亚区块内形成的多相阿克恰劳花岗岩块的形成模型。这项工作基于主要和微量元素组成、地质年代、矿物学和同位素地球化学研究的结果。阿克扎伊劳地块的形成分为三个阶段,与之前公认的关于该侵入体的多复合和多时间起源的概念大相径庭:(1) 形成中等碱性的 A2 型白花岗岩(308-301Ma);(2) 单斜闪长岩侵入白花岗岩底部(约 295Ma),原岩部分熔化程度增加,形成正长岩和中等碱性的 I 型花岗岩(294-292Ma);(3) 在地块西部和北部侵入尖晶岩和小块碱性铁长斑岩 A1 型白花岗岩(约 289 Ma)。阿克恰劳岩块是在中上地壳约 15 Myr 内,通过与羽状亚碱性玄武质岩浆与造山构造的变质地壳原岩相互作用而形成的。
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引用次数: 0
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Petrology
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