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1.
Calcium- and aluminum-rich inclusions (CAIs), occurring in chondritic meteorites and considered the oldest materials in the solar system, can provide critical information about the environment and time scale of creation of planetary materials. However, interpretation of the trace element and isotope compositions of CAIs, particularly the light elements Li, Be, and B, is hampered by the lack of constraint on melilite-melt and spinel-melt partition coefficients. We determined melilite-melt and spinel-melt partition coefficients for 21 elements by performing controlled cooling rate (2 °C/h) experiments at 1 atmosphere pressure in sealed platinum capsules using a synthetic type B CAI melt. Trace element concentrations were measured by secondary ion mass spectrometry (SIMS) and/or laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Melilites vary only slightly in composition, ranging from Åk31-43. Results for the partitioning of trace elements between melilite and melt in three experiments and between spinel and melt in two experiments show that partition coefficients are independent of trace element concentration, are in good agreement for different analytical techniques (SIMS and LA-ICP-MS), and are in agreement with previous measurements in the literature. Partition coefficients between intermediate composition melilites and CAI melt are the following: Li, 0.5; Be, 1.0; B, 0.22; Rb, 0.012; Sr, 0.68; Zr, 0.004; Nb, 0.003; Cs, 0.002; Ba, 0.018; La, 0.056; Nd, 0.065; Sm, 0.073; Eu, 0.67; Er, 0.037; Yb, 0.018; Hf, 0.001; Ta, 0.003; Pb, 0.15; U, 0.001; Th, 0.002. Site size energetics analysis is used to assess isovalent partitioning into the different cation sites. The Young’s modulus deduced from +2 cations partitioning into the melilite X site agrees well with the bulk modulus of melilite based on X-ray diffraction methods. The changes in light element partitioning as melilite composition varies are predicted and used in several models of fractional crystallization to evaluate if the observed Li, Be, and B systematics in Allende CAI 3529-41 are consistent with crystallization from a melt. Models of crystallization agree reasonably well with observed light element variations in areas previously interpreted to be unperturbed by secondary processes [Chaussidon, M., Robert, F., McKeegan, K.D., 2006. Li and B isotopic variations in an Allende CAI: Evidence for the in situ decay of short-lived 10Be and for the possible presence of the short-lived nuclide 7Be in the early solar system. Geochim. Cosmochim. Acta70, 224-245], indicating that the trends of light elements could reflect fractional crystallization of a melt. In contrast, areas interpreted to have been affected by alteration processes are not consistent with crystallization models.  相似文献   

2.
Partitioning behavior of Sc, Ti, V, Mn, Sr, Y, Zr, Nb, Ba, La, Nd, Sm, Eu, Gd, Dy, Ho, Yb, Hf, and Pb between dacitic silicate melt and clinopyroxene, orthopyroxene, and plagioclase has been determined based on laser ablation-inductively coupled plasma mass spectrometric (LA-ICPMS) analysis of melt inclusions and the immediately adjacent host mineral. Samples from the 1988 eruption of White Island, New Zealand were selected because petrographic evidence suggests that all three mineral phases are in equilibrium with each other and with the melt inclusions. All three phenocryst types are found as mineral inclusions within each of the other phases, and mineral inclusions often coexist with melt inclusions in growth-zone assemblages. Compositions of melt inclusions do not vary between the different host minerals, suggesting that boundary layer processes did not affect compositions of melt inclusions and that post-trapping modifications have not occurred.Partition coefficients were calculated from the host and melt inclusion compositions and results were compared to published values. All trace elements examined in this study except Sr are incompatible in plagioclase, and all measured trace elements except for Mn are incompatible in orthopyroxene. In clinopyroxene, Sc, V, and Mn are compatible, and Y, Ti, HREE, and the MREE are only slightly incompatible. Most partition coefficients overlap the wide range of values reported in the literature, but the White Island data are consistently at the lower end of the range in published values. Results from the literature obtained using modern microanalytical techniques such as secondary ion mass spectrometry (SIMS) or proton induced X-ray emission spectroscopy (PIXE) also fall at the lower end of the published values, whereas partition coefficients determined from bulk analysis of glass and crystals separated from volcanic rocks typically extend to higher values. Rapid crystal growth-rates, crystal zonation, or the presence of accessory mineral inclusions in phenocrysts likely accounts for the wide range and generally higher partition coefficients obtained using bulk sampling techniques. The results for 3+ cations from this study are consistent with theoretical predictions based on a lattice strain model for site occupancy. The results also confirm that the melt inclusion-mineral (MIM) technique is a reliable method for determining partition coefficients, as long as the melt inclusions have not experienced post-entrapment reequilibration.  相似文献   

3.
High-pressure metamorphic (HPM) rocks (derived from igneous protoliths) and their metasomatised rinds from the island of Syros (Greece) were analysed for their B and Cl whole-rock abundances and their H2O content by prompt-gamma neutron-activation analysis (PGNAA) and for their Li and Be whole-rock abundances by ICP-OES. In the HPM rocks, B?/Be and Cl?/Be ratios correlate with H2O contents and appear to be controlled by extraction of B and Cl during dehydration and prograde metamorphism. In contrast, samples of the metasomatised rinds show no such correlation. B?/Be ratios in the rinds are solely governed by the presence or absence of tourmaline, and Cl?/Be ratios vary significantly, possibly related to fluid inclusions. Li/Be ratios do not correlate with H2O contents in the HPM rocks, which may in part be explained by a conservative behaviour of Li during dehydration. However, Li abundances exceed the vast majority of published values for Li abundances in fresh, altered, or differentiated oceanic igneous rocks and presumably result from metasomatic enrichment of Li. High Li concentrations and highly elevated Li/Be ratios in most metasomatised samples demonstrate an enrichment of Li in the Syros HP mélange during fluid infiltration. This study suggests that B and Cl abundances of HPM meta-igneous rocks can be used to trace prograde dehydration, while Li concentrations seem to be more sensitive for retrograde metasomatic processes in such lithologies.  相似文献   

4.
Despite the growing interest for Li and B as geochemical tracers, especially for material transfer from subducting slabs to overlying peridotites, little is known about the behaviour of these two elements during partial melting of mantle sources. In particular, mineral/melt partition coefficients for B and to a lesser extent Li are still a matter of debate. In this work, we re-equilibrated a synthetic basalt doped with ~10 ppm B and ~6 ppm Li with an olivine powder from a spinel lherzolite xenolith at 1 GPa–1,330°C, and we analyzed Li and B in the run products by secondary ion mass spectrometry (SIMS). In our experiment, B behaved as a highly incompatible element with mineral/melt partition coefficients of the order of 10−2 (D ol/melt = 0.008 (0.004–0.013); D opx/melt = 0.024 (0.015–0.033); D cpx/melt = 0.041 (0.021–0.061)), and Li as a moderately incompatible element (D ol/melt = 0.427 (0.418–0.436); D opx/melt = 0.211 (0.167–0.256); D cpx/melt = 0.246 (0.229–0.264)). Our partition coefficients for Li are in good agreement with previous determinations. In the case of B, our partition coefficients are equal within error to those reported by Brenan et al. (1998) for all the mineral phases analyzed, but are lower than other coefficients from literature for some of the phases (up to 5 times for cpx). Our measurements complement the data set of Ds for modelling partial melting of the upper mantle and basalt generation, and confirm that, in this context, B is more incompatible than previously anticipated.  相似文献   

5.
ABSTRACT

Previous study of subducted continental crust within the Luliang Shan terrane in Northwest China has documented metasomatic formation of thick, hydrated phengite + garnet-rich selvages at the interface between mafic eclogite blocks and quartzofeldspathic host gneiss. Whole rock concentrations of Cs and Ba within the selvage are enriched by two orders of magnitude relative to the eclogite blocks and host gneiss. We performed in situ ion microprobe analyses of Li, Be, B, Rb, Sr, Cs and Ba and δ11B of phengite within the Luliang Shane terrane to better constrain the source(s) of the infiltrating fluid. The phengite within the selvage are enriched in Li, Cs and Ba and yield δ11B values between ?30‰ and ?9‰, values that are lower than mantle values. High Ba/Rb, Cs/Rb coupled with low B/Be, B/Li and highly negative δ11B values indicate that the high-pressure fluid that formed the selvage was derived from highly devolatilized rocks within the subduction channel. In contrast, muscovite, which crystallized in the adjacent host gneiss during a subsequent lower pressure phase of fluid infiltration at approximately 0.9 GPa depths, has much lower Li, Cs and Ba relative to the high-pressure phengite. These retrograde muscovite have very high concentrations of B (up to 5500 ppm) and Be (up to 50 ppm) and high (?2 to +8‰) δ11B values that are consistent with crystallization from a fluid derived from shallower and less devolatilized regions of the subduction zone. Additional host gneiss samples, regionally distributed and kilometres away from the studied area lack the B-rich signature and indicate that the late stage fluids were likely localized to the region near the studied traverse.  相似文献   

6.
The Totalp-Platta-Malenco ophiolites in the Eastern Central Alps offer a unique opportunity to study the behaviour of Li, Be and B in ultramafic rocks in response to serpentinization and to progressive Alpine metamorphism. These units represent the remnants of a former ocean-continent transition that was intensely serpentinized during exposure on the Jurassic seafloor of the Ligurian Tethys. From north to the south, three isograd reactions (lizardite⇒antigorite+brucite;lizardite+talc⇒antigorite;lizardite+tremolite⇒antigorite+diopside) have been used to quantify the evolution of the light element content of metamorphic minerals. We determined the Li, Be and B concentrations in major silicate minerals from the ultramafic bodies of Totalp, Platta and Malenco by secondary ion mass spectrometry. Mantle minerals have Be concentrations (e.g. <0.001-0.009 μg/g in olivine) similar to the metamorphic minerals that replace them (e.g. <0.001-0.016 μg/g in serpentine). The mantle signature of Be is thus neither erased during seafloor alteration nor by progressive metamorphism from prehnite-pumpellyite to epidote-amphibolite facies. In contrast, the Li and B inventories of metamorphic minerals are related to the lizardite-to-antigorite transition. Both elements display higher concentrations in the low-temperature serpentine polymorph lizardite (max. 156 μg/g Li, max. 318 μg/g B) than in antigorite (max. 0.11 μg/g Li, max. 12 μg/g B). Calculated average B/Li ratios for lizardite (∼1395) and antigorite (∼115) indicate that Li fractionates from B during the lizardite-to-antigorite transition during prograde metamorphism in ultramafic rocks. In subduction zones, this signature is likely to be recorded in the B-rich nature of forearc fluids.Relative to oceanic mantle the Be content of mantle clinopyroxene is much higher, but similar to Be values from mantle xenoliths and subduction-related peridotite massifs. These data support previous hypothesis that the mantle rocks from the Eastern Central Alps have a subcontinental origin. We conclude that Be behaves conservatively during subduction metamorphism of ultramafic rocks, at least at low-temperature, and thus retains the fingerprint of ancient subduction-related igneous events in mantle peridotites.  相似文献   

7.
Thirty five minor and trace elements (Li, Be, B, Sc, Cu, Zn, Ga, Ge, As, Rb, Nb, Mo, Ag, Cd, In, Sn, Sb, Cs, Ba, La, Ce, Nd, Sm, Tb, Ho, Tm, Lu, Hf, Ta, W, Tl, Pb, Bi, Th and U) in experimentally produced near-liquidus phases, from a primitive nelpheline basanite from Bow Hill in Tasmania (Australia), were analysed by LAM ICP-MS. A number of halogens (F, Cl and I) were also analysed by electron microprobe. The analyses were used to determine mineral/melt partition coefficients for mica, amphibole, garnet, clinopyroxene, orthopyroxene and olivine for conditions close to multiple saturation of the basanite liquidus with garnet lherzolite (approximately 2.6 GPa and 1,200°C with 7.5 wt% of added H2O). A broader range of conditions was also investigated from 1.0 GPa and 1,025°C to 3.5 GPa and 1,190°C with 5–10 wt% of added H2O. The scope and comprehensiveness of the data allow them to be used for two purposes, these include the following: an investigation of some of the controlling influences on partition coefficients; and the compilation of a set partition coefficients that are directly relevant to the formation of the Bow Hill basanite magma by partial melting of mantle peridotite. Considering clinopyroxene, the mineral phase for which the most data were obtained, systematic correlations were found between pressure and temperature, mineral composition, cation radius and valence, and ΔG coulb (the coulombic potential energy produced by substituting a cation of mismatched valence into a crystallographic site). ΔG coulb is distinctly different for different crystallographic sites, including the M2 and M1 sites in clinopyroxene. These differences can be modelled as a function of variations in optimum valence (expressed as 1 sigma standard deviations) within individual M1 and M2 site populations.  相似文献   

8.
Prosperous granite (Rb-Sr 2520±25 Ma) occurs as several plutons (1–380 km2 outcrop area) in a thick succession of metamorphosed greywacke-mudstone of the Yellowknife Supergroup. The average mineral content of the Sparrow pluton (in vol.%) is quartz (32), plagioclase (31), K-feldspar (24), muscovite (9), biotite (3), and apatite (<1). Average trace-element concentrations (in ppm) are Li (140), Be (4), B (28), Zn (47), Rb (250), Sr (76), Zr (75) and Ba (360). The central portion of the pluton is slightly richer in K, Sr, and Ba than the margin. Li is concentrated in mica (Li in biotite/Li in muscovite=4.7), and Be and B in muscovite and plagioclase. Countless pegmatite dikes occur in the Sparrow pluton and in schist-hornfels to the east; the outer limit is marked by the cordierite isograd, 9 km from the granite contact. Dikes vary greatly in size (1 km to a few cm in length), in mineral content (quartz, albite, K-feldspar, muscovite, tourmaline, beryl, spodumene), in major element composition (especially the NaK ratio), and in trace-element content (Li 18–5000 ppm, Be 5–260 ppm, B 20–150 ppm). Compared with Prosperous granite, the pegmatite bodies are richer in P and Rb, and poorer in Ti, Fe, Mg, Zr, and Ba. Dikes rich in tourmaline, beryl, and spodumene occur in overlapping zones situated progressively farther from the centre of the Sparrow pluton. The composition of tourmaline is related to host rock; the highest concentrations of Fe and Zn occur in crystals from pegmetite and the highest concentrations of Mg and V occur in crystals from tourmalinized schist, while those from granite and quartz veins occupy on intermediate position. Complex compositional zoning is present in some tourmaline crystals in pegmatite. Estimates of temperature (500°–600° C) and pressure (2–4 kb) of granite emplacement, based on the distribution of andalusite and sillimanite in the contact rocks, suggest that the final stage of granite emplacement occurred at sub-solidus conditions. A vaportransport model is proposed to explain the widespread distribution of the pegmatite dikes and their extreme compositional variability. Some of the pegmatite constituents, including Li, Be, and B, were possibly derived from Yellowknife graywacke and mudstone.  相似文献   

9.
The trace-element signature that cordierite (Crd) imparts to silicic magmas was evaluated by experiment using metapelite mineral mixtures to produce cordierite-bearing peraluminous granitic melts at 200 MPa (PH2O), from 700 to 850 °C. Most elemental partition coefficients vary with T. Beryllium is strongly compatible, with DBeCrd/melt values decreasing linearly from 202.0 to 6.7 as T rises from 700 to 850 °C. Manganese is compatible (DMnCrd/melt=7.67 to 1.92 over the same range of T), and shows similar values to those reported for biotite in silicic melts. Incompatible components include Li, Rb, B, F and P, although Cs is nearly compatible in cordierite, especially at higher T (DCsCrd/melt=~0.19 to 0.60) where the large alkalis are better accommodated structurally. Cordierite appears to be the most effective crystalline reservoir of Be and Cs in metapelites and their anatectic melts. Natural data support the hypothesis that Crd, when present in granitic melts, sequesters Be, Cs and, in the absence of garnet, Mn. S-type granitic rocks containing Crd show consistently low Be contents (mean=0.8 ppm Be with an average range of <1 to 1.20) whereas Crd-free granites (e.g., containing accessory garnet) exhibit distinctly higher Be contents (mean=6 ppm Be with an average range of 3 to 12). These values increase further in evolved facies (mean=69 ppm Be with a an average range of 11 to 145) which commonly give rise to beryl-bearing pegmatites. Whole-rock signatures of Be discriminate source environments of silicic magmas at a resolution equal to the boundaries of the cordierite stability field - e.g., at the P-T-X conditions where cordierite gives rise to garnet+aluminum silicate. Cordierite-bearing granitic rocks contain low Cs contents (mean=1.8 ppm Cs) compared to the Crd-free equivalents (mean=18 ppm Cs). Mn contents also correlate with the presence (mean=0.01 wt% MnO) or absence of Crd (mean=0.09 wt% MnO). Depending on its contribution to anatexis, cordierite may either give or take S-type chemical character from granitic liquids, resulting in a distinctive Crd-associated group of S-type elements. This signature is different from that of micas (high Li, F and, to a lesser degree, Be and Mn). Whole-rock compositions of granites, coupled with notable absences of beryl in their associated pegmatites, indicate that a sizable population of S-type granites originated from Crd-bearing sources. The normative Crd component of silicic peraluminous melts is Д wt% to 850 °C. Higher modal contents of cordierite reflect either restite entrainment or peritectic reactions which produce Crd after magma ascent to shallow depths. The distinctive trace-element signature of cordierite now provides improved resolution of the source mineralogy for S-type magmas.  相似文献   

10.
熔体-溶液体系中元素分配系数:新资料及其研究方向   总被引：2，自引：0，他引：2  
基于近几年来国内外学者测得的熔体-溶液体系中F、Cl、P、CO_2、B、Au、Pb、Zn、Cu、Fe、Mg、Li、Rb、Cs、K、Na、Ca、Sr、Ba、Co、Ni、Be、Mo、W、Si、Al、REE、Sc、Ti、U、Th、Zr、Hf、Nb、Pt、Ir、Pd等元素的分配系数,从元素性质、溶液成分(阴离子和阳离子)、熔体成分和物理化学条件等方面进一步分析总结了分配系数变化规律,并提出了预测未知元素分配系数的元素性质准则、溶液成分准则、熔体成分准则和物理化学条件准则,最后指出了这一研究领域今后的研究方向。  相似文献   

11.
The analytical capabilities of laser ablation (LA)-ICP-MS in determining Li, Be and B at trace levels in geological samples have been tested on a series of glass reference materials and natural samples. The LA-ICP-MS instrument used consisted of a sector-field ICP-MS coupled with a laser ablation microprobe operating at either 266 or 213 nm wavelength. Reference glasses from NIST (SRM 612, 614 and 616) and MPI-DING (KL2-G, ML3B-G, StHs6/80-G, GOR128-G, GOR132-G, T1-G and ATHO-G) were selected to develop the analytical method and to assess the best instrumental configuration. A series of calcic amphiboles with different Li, Be and B concentrations were also analysed using both LA-ICP-MS and SIMS to test the applicability of the method to natural minerals. Results indicated that with a spot size of 40 μm the agreement between measured and reference values of Li, Be and B is generally better than 10% for NIST SRM 612 and 20% for NIST SRM 614. Average reproducibility at the 2s level was 10% for Li, 20% for Be and 15% for B. Limits of detection were approximately 100 ng g-1 for Be and B and 200 ng g-1 for Li. These results were confirmed by analyses carried out on natural amphiboles and compared well in terms of precision and accuracy with those commonly achieved by SIMS.  相似文献   

12.
微量元素在幔源矿物与热液之间分配系数的差异是造成地幔不均一的一个重要因素，对于认识地球演化、元素的分异和板块构造具有重要的意义。热液的组成、矿物的结构、温度、压力以及氧逸度都与分配系数密切相关。不同微量元素在相同矿物或热液中的分配系数存在差别，而相同的元素在不同矿物中的分配系数也可能出现很大的变化，这是研究微量元素分异和不同地幔端员形成的理论基础。在较低的温度和压力下，热液的组成对分配系数的影响很大，随着温度和压力的升高，热液组成的影响逐渐减弱，而矿物的组成与结构的影响逐渐增大。由于分配系数影响因素的复杂性，因此在考虑地球深部微量元素的迁移和分异时需慎重对待。  相似文献   

13.
The mineral phases of 33 eclogite and garnet clinopyroxenite samples from various tectonic settings were analysed for Li by secondary ion mass spectrometry (SIMS). In all samples, Li is preferentially incorporated into clinopyroxene (0.4 to 80 µg/g), whereas co-existing garnet contains only minor amounts of Li (0.01 to 3.7 µg/g). When present, glaucophane shows Li abundances which are similar to those of clinopyroxene, but phengite contains significantly less Li than clinopyroxene. Additional phases, such as amphibole, quartz, clinozoisite and kyanite, have low Li concentrations (<1 µg/g). No correlation is apparent between the Li contents and major-element compositions of clinopyroxene or garnet. On the basis of both measured Li concentrations in clinopyroxene and estimated Li abundances in the whole rocks, the investigated samples can be subdivided into high-Li and low-Li groups. These groups coincide with the mode of origin of the rocks. Metabasaltic (metagabbroic) eclogites from high-pressure terranes belong to the high-Li group whereas, except for one eclogite, all kimberlite- and basanite-hosted xenoliths have low Li contents. Samples from eclogites and garnet clinopyroxenites associated with orogenic peridotites fall into both groups. It is suggested that the high-Li eclogites originated from basaltic oceanic crust whereby the notable Li enrichment of some samples was probably caused by low-temperature hydrothermal alteration prior to subduction. Furthermore, the low-Li eclogites and garnet clinopyroxenites may represent high-pressure cumulates from mafic melts percolating through the mantle.  相似文献   

14.
The concentrations and isotopic compositions of lithium, beryllium, and boron, analyzed in situ by ion microprobe in 66 spots of a type B1 Ca-Al-rich inclusion (CAI 3529-41) from the Allende meteorite, are reported. Large variations are observed for both the Li and the B isotopic ratios with 7Li/6Li ranging from 9.2 ± 0.22 to 12.22 ± 0.43 (a ≈250‰ range in δ7Li values) and 10B/11B ranging from 0.2468 ± 0.0057 to 0.4189 ± 0.0493 (a 410‰ range in δ11B values). The very low Li concentrations (<1 ppb) observed in several anorthite and fassaite grains require that a correction for the contribution of spallogenic Li produced during irradiation of the Allende meteoroid by galactic cosmic rays (GCR) be made (after this correction 7Li/6Li ranges from 9.2 ± 0.22 to 13.44 ± 0.56, i.e., a ≈350‰ range in δ7Li values). In 3529-41, the 10B/11B ratios are positively correlated with 9Be/11B in a manner indicating the in situ decay of short-lived 10Be (half-life = 1.5 Ma) with a 10Be/9Be ratio at the time of formation of the CAI of 8.8 ± 0.6 × 10−4, which is in agreement with previous findings [McKeegan, K.D., Chaussidon, M., Robert, F., 2000. Incorporation of short-lived 10Be in a calcium-aluminum-rich inclusion from the Allende meteorite. Science289, 1334-1337]. The present detailed investigation demonstrates that only minor perturbations of the 10Be-10B system are present in 3529-41, contrary to the 26Al/26Mg system for which numerous examples of isotopic redistribution following crystallization were observed [Podosek, F.A., Zinner, E.K., MacPherson, G.J., Lundberg, L.L., Brannon, J.C., Fahey, A.J., 1991. Correlated study of initial 87Sr/86Sr and Al-Mg systematics and petrologic properties in a suite of refractory inclusions from the Allende meteorite. Geochim. Cosmochim. Acta55, 1083-1110]. Petrographically based criteria were developed to identify within the 66 analyzed spots in 3529-41, those where post-magmatic perturbation of the Li and Be distributions occurred. Li and Be concentrations measured in different analytical spots are compared with those predicted by using experimentally determined partition coefficients according to a model of closed-system crystallization of the CAI melt. These criteria show that 56% of the spots in melilite, 38% in anorthite, and 8% in fassaite suffered post-crystallization perturbations of Li and/or Be distributions. In the remaining spots, which do not show obvious indication of redistribution of Li or Be, the 7Li/6Li isotopic variations (corrected for GCR exposure) are positively correlated with9Be/6Li suggesting the in situ decay of now-extinct 7Be. The derived isochron implies that at the time of its formation, the CAI melt had a 7Be/9Be ratio of 0.0061 ± 0.0013 and a 7Li/6Li ratio of 11.49 ± 0.13. In contrast, all the spots in 3529-41, which do show evidence for post-magmatic redistribution of Li and Be, have relatively constant 7Li/6Li, averaging 11.72 ± 0.56, which is consistent with mass balance calculations for Li isotopic homogenization in the CAI after the decay of 7Be. The incorporation of live 7Be in 3529-41 requires, because of the very short half-life of this nuclide (53 days), that it be produced essentially contemporaneously with the formation of the CAI. Therefore, the irradiation processes responsible for production of 7Be must have occurred within the solar accretion disk. Calculations developed in the framework of the x-wind model [Gounelle, M., Shu, F.H., Shang, H., Glassgold, A.E., Rehm, E.K., Lee, T., 2004. The origin of short-lived radionuclides and early Solar System irradiation (abstract). Lunar Planet. Sci.35, 1829] reproduce the 7Be and 10Be abundances observed in 3529-41. The correlated presence of 7Be and 10Be in 3529-41 is thus a strong argument that 10Be, which is observed rather ubiquitously in CAIs, is also a product of irradiation in the early solar system, as might be a significant fraction of other short-lived radionuclides observed in early solar system materials.  相似文献   

15.
In this paper we report the results of the analysis of rare earth (REE), large-ion lithophile (LILE), and high field strength (HFSE) elements in minerals from the alkaline lamprophyre dikes of the Kola region and the Kaiserstuhl province by the local method of laser ablation inductively coupled plasma mass spectrometry. The contents of Y, Li, Rb, Ba, Th, U, Ta, Nb, Sr, Hf, Zr, Pb, Be, Sc, V, Cr, Ni, Co, Cu, Zn, Ga, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu were measured in olivine, melilite, clinopyroxene, amphibole, phlogopite, nepheline, apatite, perovskite, and the host fine-grained groundmass. The obtained data on trace element partitioning among the mineral phases of the alkaline ultrabasic rocks of the dike series indicate that the main mineral hosts for the HFSEs and REEs in alkaline picrites, olivine melanephelinites, and melilitites are perovskite and apatite comprising more than 90% of these elements. Among major rock-forming minerals, melilite, clinopyroxene, and highly magnesian amphibole make a significant contribution to the balance of REEs during the evolution of melanephelinite melts. The partition coefficients of Ni, Co, Cu, Zn, Sc, V, Cr, Ga, Y, Li, Rb, Ba, Th, U, Ta, Nb, Sr, Hf, Zr, Pb, Be, and all of the REEs were calculated for olivine, clinopyroxene, amphibole, phlogopite, nepheline, perovskite, and apatite on the basis of mineral/groundmass ratios. Variations in the composition of complex zoned clinopyroxene phenocrysts reflect the conditions of polybaric crystallization of melanephelinite melt, which began when the magmas arrived at the base of the lower crust and continued during the whole period of their ascent to the surface. The formation of green cores in clinopyroxene is an indicator of mixing between primary melanephelinite melts and phonolite magmas under upper mantle conditions. The estimation of the composition of primary melts for the rocks of the alkaline ultrabasic series of the Kola province indicated a single primary magma for the whole series. This magma produced pyroxene cumulates and complementary melilitolites, foidolites, and nepheline syenites.  相似文献   

16.
Experimental cpx/melt partitioning of 24 trace elements   总被引：46，自引：13，他引：46  
Cpx/melt partition coefficients have been determined by ion probe for 24 trace elements at natural levels in an alkali basalt experimentally equilibrated at 1,380°C and 3 GPa. One goal was to intercompare Ds for both high-field-strength elements and rare earth elements (REE) in a single experiment. Relative to the REE spidergram, Hf and Ti show virtually no anomaly, whereas Zr exhibits a major negative anomaly. Other incompatible elements (Ba, K, Nb) fall in the range of published values, as do elements such as Sr, Y, Sc, Cr and V. Pb shows a value intermediate between La and Ce. Values for Be, Li and Ga are reported for the first time, and show that Be is as incompatible as the light REEs whereas Li and Ga are somewhat more compatible than the heavy REE.  相似文献   

17.
Olivine/melt and orthopyroxene/melt rare-earth element (REE) partition coefficients consistent with clinopyroxene/melt partition coefficients were determined indirectly from subsolidus partitioning between olivine, orthopyroxene, and clinopyroxene after suitable correction for temperature. Heavy- and middle-REE ratios for olivine/clinopyroxene and orthopyroxene/clinopyroxene pairs correlate negatively with effective cationic radius, whereas those for the light REEs correlate positively with cationic radius, generating a U-shaped pattern in apparent mineral/clinopyroxene partition coefficients versus cationic radius. Lattice strain models of partitioning modified for subsolidus conditions yield negative correlations of olivine/clinopyroxene and orthopyroxene/clinopyroxene with respect to cationic radii, predicting well the measured partitioning behaviors of the heavy and middle REEs but not that of the light REEs. The light-REE systematics cannot be explained with lattice strain theory and, instead, can be explained by disequilibrium enrichment of the light REEs in melt inclusions or on the rims of olivine and orthopyroxene. Realistic light-REE partition coefficients were thus extrapolated from the measured heavy- and middle-REE partition coefficients using the lattice strain model. Light REE olivine/melt and orthopyroxene/melt partition coefficients calculated in this manner are lower than most published values, but agree reasonably well with partitioning experiments using the most recent in situ analytical techniques (secondary-ionization mass spectrometry and laser ablation inductively coupled plasma mass spectrometry). These new olivine/melt and orthopyroxene/melt partition coefficients are useful for accurate modeling of the REE contents of clinopyroxene-poor to -free lithologies, such as harzburgitic residues of melting. Finally, the application of the lattice strain theory to subsolidus conditions represents a framework for assessing the degree of REE disequilibrium in a rock.  相似文献   

18.
Partition coefficients (DBemineral/melt) for beryllium between hydrous granitic melt and alkali feldspars, plagioclase feldspars, quartz, dark mica, and white mica were determined by experiment at 200 MPa H2O as a function of temperature (650-900°C), activity of Be in melt (trace levels to beryl saturation), bulk composition, and thermal run direction. At trace levels, Be is compatible in plagioclase of An31 (1.84 at 700°C) and muscovite (1.35 at 700°C) but incompatible in biotite (0.39-0.54 from 650-800°C), alkali feldspar (0.38-0.19 from 680-850°C), quartz (0.24 at 800°C), and albite (0.10 at 750°C). The partition coefficients are different at saturation of the melt in beryl: lower in the case of plagioclase of An31 (0.89 at 700°C), muscovite (0.87 at 700°C), biotite (0.18-0.08 from 675-800°C), alkali feldspar (0.18-0.14 from 680-700°C), and quartz (0.17-0.08 from 750-800°C), but higher in the case of albite (0.37 at 750°C).With other data sources, these new partition coefficients were utilized to track, first, the distribution of Be between aluminous quartzofeldspathic source rocks and their anatectic melts, and second, the dispersion or concentration of Be in melt through igneous crystal fractionation of different magma types (e.g., S-type, I-type) up to beryl-saturated granitic pegmatites and, finally, into their hydrothermal aureoles. Among the rock-forming minerals, cordierite, calcic oligoclase, and muscovite (in this order) control the fate of Be because of the compatibility of Be in these phases. In general, beryl-bearing pegmatites can arise only after extended crystal fractionation of large magma batches (to F, fraction of melt remaining, ≤0.05); granitic magmas that originate from cordierite-bearing protoliths or that contain large modal quantities of calcic oligoclase will not achieve beryl saturation at any point in their evolution.  相似文献   

19.
朱鑫祥  刘琰 《岩矿测试》2021,(2):296-305
雪宝顶矿床位于四川省的松潘甘孜造山带中,以出产大颗粒含W-Sn-Be-F-P的矿物而闻名,前人对该矿床已经开展了大量的研究,但缺乏对粗粒矿物的主次痕量元素研究。本次研究采用X射线荧光光谱(XRF)、电子探针(EMPA)和电感耦合等离子体质谱(ICP-MS)技术对矿床中各矿物的主次痕量元素进行测试分析。结果显示,雪宝顶矿床中的绿柱石、白钨矿、锡石、白云母、萤石、磷灰石、电气石,除富含W、Sn、Be、Na、K、Ca等主要成矿元素外,还富集Li、Rb、Cs等碱金属元素和F、B、P等挥发份。其中,雪宝顶绿柱石中富含Li(3484~4243μg/g)、Rb(39.3~71.1μg/g)、Cs(2955~3526μg/g);白云母中Li、Rb和Cs元素含量分别高达4243μg/g、72.3μg/g和3526μg/g;磷灰石中除主量元素P外,F(4.48%~5.21%)含量相对较高;电气石中的B含量高达30990~32880μg/g。雪宝顶矿床中的花岗岩岩体W、Sn、Be、Li、Rb、Cs、F、B、P等元素相对富集,但CaO含量(0.46%~0.82%)相对较低。其中Li、F、B、P等元素对成矿元素在成矿流体内的富集起到了极大的促进作用。矿区内大理岩是一种富Ca的方解石大理岩,为成矿提供了大量的Ca元素,有利于粗粒矿物的大规模沉淀。因此,粗粒矿物中的W、Sn、Be、Li、Rb、Cs、F、B、P等元素主要来源于原始岩浆流体,大理岩地层为粗粒矿物提供了大量的Ca元素。  相似文献   

20.
Partition coefficients between olivine and melt at upper mantle conditions, 3 to 14 GPa, have been determined for 27 trace elements (Li, Be, B, Na, Mg, Al, Si, P, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Rb, Sr, Y, Zr, Cs, Ba, La and Ce) using secondary-ion mass-spectrometry (SIMS) and electron-probe microanalysis (EPMA). The general pattern of olivine/melt partitioning on Onuma diagrams resembles those reported previously for natural systems. This agreement strongly supports the argument that partitioning is under structural control of olivine even at high pressure. The partition coefficients for mono- and tri-valent cations show significant pressure dependence, both becoming larger with pressure, and are strongly correlated with coupled substitution into cation sites in the olivine structure. The dominant type of trace element substitution for mono- and tri-valent cations into olivine changes gradually from (Si, Mg)↔(Al, Cr) at low pressure to (Si, Mg)↔(Al, Al) and (Mg, Mg)↔(Na, Al) at high pressure. The change in substitution type results in an increase in partition coefficients of Al and Na with pressure. An inverse correlation between the partition coefficients for divalent cations and pressure has been observed, especially for Ni, Co and Fe. The order of decreasing rate of partition coefficient with pressure correlates to strength of crystal field effect of the cation. The pressure dependence of olivine/melt partitioning can be attributed to the compression of cation polyhedra induced by pressure and the compensation of electrostatic valence by cation substitution. Received: March 6, 1997 / Revised, accepted: March 12, 1998  相似文献   

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