Phenocryst H5k-2 in this chondrule has a relict core (with rhythmic P zoning layers) that was fractured and severed it is overlain by a set of differently oriented subparallel P-poor olivine layers. Strong evidence of a secondary melting event is evident in Semarkona chondrule H5k.
Sectioning of the olivine grains at particular orientations can produce apparent oscillatory zoning in P. Crystallization of mafic silicates depleted the mesostasis in FeO and MgO and enriched it in silico-feldspathic components. The skeletal olivine crystals were filled in with low-P olivine during cooling after one or more subsequent heating events, mainly involving the melting of mesostasis. In contrast, the relatively slow diffusion of P in olivine preserves original dendritic or hopper morphologies of olivine crystals these skeletal structures formed during quenching after initial chondrule melting. Such discrete layers are generally not evident in BSE images or in Fe, Cr, Ca, Al, Mg, or Mn X-ray maps because rapid diffusion of these cations in olivine at high temperatures smoothed out their initial distributions, thereby mimicking normal igneous zoning. Phosphorus X-ray maps of olivine phenocrysts in many type II (FeO-rich) porphyritic chondrules in L元.00 Semarkona and CO3.05 Y 81020 reveal multiple sets of thin dark/bright (P-poor/P-rich) layers that resemble oscillatory zoning. The minerals in meteorites can be categorized as having formed by a myriad of processes that are not all mutually distinct: (1) condensation in gaseous envelopes around evolved stars (presolar grains), (2) condensation in the solar nebula, (3) crystallization in CAI and AOI melts, (4) crystallization in chondrule melts, (5) exsolution during the cooling of CAIs, (6) exsolution during the cooling of chondrules and opaque assemblages, (7) annealing of amorphous material, (8) thermal metamorphism and exsolution, (9) aqueous alteration, hydrothermal alteration and metasomatism, (10) shock metamorphism, (11) condensation within impact plumes, (12) crystallization from melts in differentiated or partially differentiated bodies, (13) condensation from late-stage vapors in differentiated bodies, (14) exsolution, inversion and subsolidus redox effects within cooling igneous materials, (15) solar heating near perihelion, (16) atmospheric passage, and (17) terrestrial weathering. About 435 mineral species have been identified in meteorites including native elements, metals and metallic alloys, carbides, nitrides and oxynitrides, phosphides, silicides, sulfides and hydroxysulfides, tellurides, arsenides and sulfarsenides, halides, oxides, hydroxides, carbonates, sulfates, molybdates, tungstates, phosphates and silico phosphates, oxalates, and silicates from all six structural groups.