The study examined garnets in lamprophyric and carbonatitic dykes and massif melilitolites from the Devonian Kola Alkaline Carbonatite Province (North-Eastern European craton). We analyzed major and trace element compositions of garnet in 14 well-characterized samples of aillikite, carbonatite, alnöites, monchiquites, nephelinite and turjaites and correlated the garnet zoning with the sequence of magmatic crystallization and late deuteric changes. The garnets occur in all textural positions, from early phenocrysts to groundmass phases and deuteric pseudomorphs. The garnets are calcic and classified into five compositional types, 1) high-Zr, 2) high-Ti, 3) medium-Ti, 4) low-Ti, and 5) high-Al. These garnet types combine in distinct ways comprising four zoning patterns (turjaite, nephelinite, monchiquite and carbonate-related) repeated in different rock types. Fractional crystallization controls the observed garnet evolution from high-Ti and high-Zr to garnets poorer in Ti, but richer in Al. Garnets progressing from magmatic to deuteric crystallization evolve from heavy rare earth elements (HREE)-enriched to light rare earth elements (LREE)-enriched and become depleted in trace elements. We interpret high-Zr garnets as antecrysts crystallized from deep alkaline carbonate-rich melts and subsequently destabilized in evolved shallow lamprophyric melts. High-Al garnets have late magmatic or deuteric origin as they replace melilite or carbonate, have low Y/Ho ratio and occur only in a location where carbonatites formed by melt and fluid immiscibility. Significant compositional changes accompanying magmatic crystallization and variations in accessory mineralogy in a single rock type result in a very wide range of major and trace element compositions of garnets and complicate their use as petrogenetic indicators.

该研究检查了来自泥盆纪科拉碱性碳酸岩省（东北欧克拉通）的陨石岩和碳酸岩岩脉以及块状黄长石岩中的石榴石。我们分析了 14 个特征明确的埃利长石、碳酸盐岩、钠长石、monchiquites、霞长石和 turjaites 样品中石榴石的主要和微量元素组成，并将石榴石分带与岩浆结晶和晚期氘化变化的顺序相关联。石榴石出现在所有结构位置，从早期的斑晶到基质相和氘假晶。石榴石是钙质的，分为五种成分类型：1) 高锆、2) 高钛、3) 中钛、4) 低钛和 5) 高铝。这些柘榴石类型以不同的方式组合，包括四种分区模式（turjaite、nephelinite、monchiquite 和碳酸盐相关）在不同的岩石类型中重复出现。分步结晶控制观察到的石榴石从高钛和高锆到贫钛但富含铝的石榴石的演化。从岩浆结晶到氘结晶的石榴石从富含重稀土元素 (HREE) 演变为富含轻稀土元素 (LREE)，然后贫化微量元素。我们将高锆石榴石解释为从富含碱性碳酸盐的深层熔体中结晶出来的前晶，随后在演化的浅陨岩熔体中不稳定。高铝石榴石具有晚期岩浆或氘化成因，因为它们取代了黄长石或碳酸盐，具有低 Y/Ho 比并且仅出现在由熔体和流体不混溶形成碳酸盐岩的位置。