Partitioning of trace elements between minerals crystallized from Ca-rich Si-undersaturated melts is constrained for the first time in samples of coarse combustion metamorphic (CM) melt rocks (paralavas) from the Hatrurim Formation. The partition coefficients of trace elements (including REE) in wollastonite, rankinite, cuspidine, Ti-andradite, melilite solid solutions, kalsilite, and fluorapatite are calculated on the basis of their contents determined by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Most of REE are hosted by fluorapatite (≤ 900 ppm ΣREE), garnet (≤ 600 ppm), and cuspidine (≤ 300 ppm), while other phases contain < 100 ppm of total REE. Sr is found in all minerals except garnet, with its contents reaching 7500 ppm in melilite, 5500 ppm in fluorapatite, 4500 ppm in rankinite, 2150 ppm in wollastonite, 2000 ppm in cuspidine, and 800 ppm in kalsilite. High-field strength elements (HFSE) occur in cuspidine (up to 2100 ppm U, 1600 ppm Zr, 1300 ppm Ti, and 200 ppm Nb) and garnet (up to 3000 ppm Zr, 600 ppm Y, 350 ppm HREE and Sc, and 130 ppm Nb). Melilite is the principal host of Zn (≤ 17,000 ppm), Ni (≤ 2100), Cu (≤ 1200), Mn (≤ 750), Co (≤ 100), and Ga (≤ 65). It also bears Ba (up to 5500 ppm), while the amount of Ba reaches 8500 ppm in kalsilite, along with ≤ 1350 Rb. The partition coefficients of trace elements for all listed minerals were calculated. Isomorphic substitutions in melilite are controlled by structural positions at three sites (Ca, T1, and T2) which can accommodate Na, Sr, and Ba (Ca); Zn, Co, Ni, Cu (T1); Fe³⁺, and Ga (T2). Melilite crystallized from CM melts lacks significant amounts of REE and HFSE. The obtained partition coefficients of trace elements in CM melilite are consistent with the available estimates for minerals from igneous alkaline complexes and thus have implications for trace element partitioning in Ca-rich Si-undersaturated melts. The partitioning patterns of trace elements during the crystallization of CM melts mainly depend on the crystal chemistry of minerals.