Incompatible element

About: Incompatible element is a research topic. Over the lifetime, 2420 publications have been published within this topic receiving 154052 citations.

New perspectives on the origin of olivine-rich troctolites and associated harrisites from the Ligurian ophiolites (Italy)

Abstract: The mid-ocean ridge (MOR)-type gabbroic sequences from the Internal Ligurian ophiolites include olivine-rich troctolite lenses up to tens of metres thick. For one of these lenses, a portion of metre-scale thickness characterized by skeletal to dendritic olivines (harrisites) was observed near the contact with host gabbros. Spinels from the olivine-rich troctolites locally include Ti-pargasite to kaersutite frequently associated with phlogopite to Na-phlogopite. Spinel-hosted amphibole displays rare earth element (REE) patterns characterized by a negative Eu anomaly, thereby recording a magmatic process associated with plagioclase segregation. The amphiboles show variable depletion of light REE (LREE) relative to middle REE (MREE), and heavy REE (HREE) that are weakly enriched to depleted with respect to MREE. Crystallization of the inclusion-bearing spinels is attributed to cooling of hybrid melts that originated by interaction between primitive melts and gabbro-related melts relatively rich in SiO 2 and incompatible elements. Clinopyroxene and amphibole from the harrisites show extensive variability for trace element compositions, albeit characterized by subparallel incompatible element patterns. This chemical variability was most probably acquired in response to rapid crystal growth related to undercooling of the harrisite parental melt. We propose that the melt undercooling was related to interaction of a primitive melt batch with a gabbroic crystal mush. Supplementary material : Details of the analytical technique are available at http://doi.org/10.6084/m9.figshare.c.3284312

Subduction-modified subcontinental mantle in South China: Trace element and isotope evidence in basalts from Hainan Island

Abstract: Cenozoic lavas from Hainan Island, South China, comprise quartz tholeiite, olivine tholeiite, alkali basalt, and basanite and form a continuous, tholeiite-dominated, compositional spectrum. Highly incompatible elements and their relationships with isotopes in these lavas are shown to be useful in evaluating mantle-source composition, whereas modeling suggests that ratios of elements with bulk partition coefficients significantly larger than those of Nb and Ta may be sensitive to partial melting. Th/Ta and La/Nb ratios of alkali basalts are lower than those of tholeiites, and they are all lower than those of the primitive mantle. These ratios correlate positively with207Pb/204Pb and87Sr/86Sr ratios. Such relationships can be explained by mixing of depleted and enriched source components. A depleted component is indicated by alkali basalt compositions and is similar to some depleted OIB (PREMA). The enriched component, similar to sediment compositions, is indicated by tholeiites with high LILE/HFSE,207Pb/204Pb, and87Sr/86Sr ratios.

Mineralogy and crystallization history of a highly differentiated REE-enriched hypabyssal rhyolite: Round Top laccolith, Trans-Pecos, Texas

Abstract: The Round Top hypabyssal rhyolite laccolith is a highly evolved magmatic system, enriched in incompatible elements including REE [Rare Earth Element(s)], U, Be, and F. The Round Top intrusion is part of a series of Paleogene intrusions emplaced as the Sierra Blanca Complex. These intrusions are situated within long-lived, complex tectonic regimes that have been subjected to regional compression and subduction, punctuated by extensional bimodal volcanism. The enrichment in the rhyolite that comprises Round Top is the result of the prolonged removal of compatible elements from the source magma chamber through the emplacement of earlier magmatic events. With the emplacement of each sequential laccolith, the F-rich source magma became more enriched in incompatible elements, with increasing HREE [Heavy Rare Earth Elements(s)] concentrations. The emplacement of Round Top as a laccolith (versus that of an extrusive rhyolitic flow) facilitated the retention of the volatile-rich vapor phase within the magma, forming ubiquitous REE-bearing minerals, mainly yttrofluorite and yttrocerite. The high temperature mineral-vapor phase alteration of the feldspar groundmass was essential to the formation of REE minerals, where the pervasive open pore space was occupied by the late-crystallizing minerals. These late-forming REE-bearing minerals also occur as crystals associated with other accessory and trace phases, as inclusions within other phases, along grain boundaries, and along fractures and within voids. The rhyolite at Round Top and other laccolith intrusions in the Sierra Blanca Complex represent a new sub-type of magmatic rare earth element hosting system.

Tectonic Setting of Ordovician Volcanic Rocks in Northwestern Xiaoxing' anling, Heilongjiang Province

Abstract: he Ordovician volcanic rocks,occurring in northwes tern Xiaoxing'anling,Heilongjiang Province,have the following features:1. They generally belong to calc-alkaline seriers on Na2O+K2O+K2O-SiO2 plot and AFM diagram despite strong potassic,silicic and spilite aftemation. They mainly belong to CAB on TiO2-MnO×10- P2O5×10 diagram.2. NMORB-normalized incompatible element distributions of volcanic rocks in this area are similar to that of continental-margin arc Cafe-alkaline series basalt. Their differences are that volcanic rocks in this area have high TI,Ta,Nb, Ce and low Cr. High Th, Ta,Nb contents indicate that the magma was composed of rutile, sphene and zircon that enriched in Th, Ta, Nb, Ce. Low Cr reflects that magma came from pert-melting upper mantle.3. Rare earth element distribution patterns of volcanic rocks are similar to that of island arc cafe-alkaline series basalt. Alternation resulted in ion of Ca2+ and depletion of Uranium.So the authors think that middle Ordovician volcanic rocks were formed in continental-margin arc serring relating to plate subduction.

Mineral chemistry, geochemistry and U-Pb SHRIMP zircon data of the Yangxin monzonitic intrusive in the foreland of the Dabie orogen

Abstract: The Yangxin composite intrusive consists of three generations of plutons, among which 90% are the second generation intrusions. The second generation intrusion has U-Pb SHRIMP zircon age of 134±2 Ma, substantially younger than the early stage of the Yanshanian. Amphibole and biotite, major mafic minerals in the Yangxin plutons, are rich in magnesium, suggesting a deep source of their parental magma, possibly derived from the upper mantle. Whole rock geochemical data on these rocks show that they have high Al 2 O 3 (15.92%―16.38%), relatively high alkali (Na 2 O+K 2 O = 6.95%―7.37%) and higher Na 2 O contents than K2O (Na 2 O/K 2 O = 1.47―1.94). They also have high Sr contents (816―897 mg/g) are enriched in strong incompatible elements such as Rb, U, Th, K and LREE, but depleted in HREE and Y. Strong fractionation of LREE from HREE as indicated by high (La/Yb)N ratios ranging from 17.83 to 20.86. Although with little difference, the whole characteristics of the Yangxin intrusive body are greatly similar to the adakite, referring that the formation of the parental magma may relate with the partial melting of the basalt underplating from the mantle after delamination of the mountain root of the Dabie orogen. The body has been uplifted about 5 km since cooling concretion, the average rate was only about 0.04 mm/a，much slower than that of the Dabie orogen in late Mesozoic, but the rates of denudation in two area are similar in Cenozoic.