Abstract We estimate the mantle source compositions for mantle plumes and, by implication, Earth’s lower mantle by: (1) measuring trace (e.g, Sc, V, Cu) and minor (e.g., Ca, Mn, Ni) element concentrations of high-forsterite olivine grains from several plume localities, (2) estimating the parent liquid compositions from which they crystallized, (3) calculating mantle potential temperatures and degrees of partial melting, and (4) estimating trace element compositions of depleted and enriched mantle sources. Our sample set includes two continental flood basalt provinces (Emeishan and Deccan), a flood basalt that erupted in a continental rift setting (Baffin Island), our type example of a thermal mantle plume (Hawaii), and lavas from the Siqueiros Transform at the East Pacific Rise, which represent the mid-ocean ridge system. We also present olivine (Ol) compositions for peridotite xenoliths from Kilbourne Hole, New Mexico, U.S.A., which are commonly used as primary and secondary analytical standards. We find that trace elements in lava-hosted olivine grains are too far removed from their mantle source to provide anything but greatly hindered views of such. Olivine compositions reflect not only evolving liquid compositions (including partial melting conditions and later fractionation), but also evolving O1+liq partition coefficients, which mostly increase with decreasing T during crystallization. Mantle compositions, delimited by maximum forsterite contents and estimates of parental magmas (and experimentally determined partition coefficients) indicate that our selected plumes reflect some combination of (1) a depleted mantle source that is quite similar to that obtained by other methods and (2) a variably enriched plume source that is more enriched than current estimates of pyrolite. The enriched plume mantle sources can be explained remarkably well as a mixture of subducted mid-ocean ridge basalt (MORB; Gale et al. 2013) and depleted MORB mantle (DM; Salters and Stracke 2004), with MORB:DMM ratios of 1:5 to 1:4. These ratios are most sensitive to estimates of melt fraction where plume parental magmas are last equilibrated with their mantle source, but are nonetheless consistent across a wide range of chemically very different elements, and estimates of MORB and DM obtained by very different means. Baffin Island is of particular interest. Like prior studies, we verify a high mantle potential temperature (Tp) of 1630 °C (compared to Tp = 1320–1420 °C for MORB from Cottrell and Kelley 2011 for O1 of Fo89.3–91.4). The Baffin source is also within error the same as DM with respect to trace elements, although still isotopically distinct; Baffin appears to be sourced in something that is akin to DMM that lies at the base of the mantle, where plumes acquire their excess heat. Thus while part of our analysis supports the concept of a “slab graveyard” at the bottom of the lower mantle (e.g., Wyession 1996), that cemetery is by no means ubiquitous at the CMB: subducted slabs are either unevenly interred, or efficiently excavated by later upwellings.

mafic to ultramafic rocks. They may contain minor amounts of other elements including chromium, manganese, cobalt or nickel. In mineralogy and gemology Serpentine subgroup (part of the kaolinite-serpentine group in the category of phyllosilicates) are greenish, brownish, or spotted minerals commonly found in serpentinite. They are used as a source of magnesium and asbestos, and as decorative stone. The name comes from the greenish color and smooth or scaly appearance from the Latin serpentinus, meaning "snake-like". Serpentine subgroup is a set o Serpentine subgroup (part of the kaolinite-serpentine group in the category of phyllosilicates) are greenish, brownish, or spotted minerals commonly found in serpentinite. They are used as a source of magnesium and asbestos, and as decorative stone. The name comes from the greenish color and smooth or scaly appearance from the Latin serpentinus, meaning "snake-like". Serpentine subgroup is a set of common rock-forming hydrous magnesium iron phyllosilicate ((Mg,Fe)3Si2O5(OH)4) minerals, resulting from the metamorphism of the minerals that are contained in mafic… Serpentine subgroup (part of the kaolinite-serpentine group in the category of phyllosilicates) are greenish, brownish, or spotted minerals commonly found in serpentinite. They are used as a source of magnesium and asbestos, and as decorative stone. The name comes from the greenish color and smooth or scaly appearance from the Latin serpentinus, meaning "snake-like". Serpentine subgroup is a set of common rock-forming hydrous magnesium iron phyllosilicate ((Mg,Fe)3Si2O5(OH)4) minerals, resulting from the metamorphism of the minerals that are contained in mafic to ultramafic rocks. They may contain minor amounts of other elements including chromium, manganese, cobalt or nickel. In mineralogy and gemology, serpentine may refer to any of the 20 varieties belonging to the serpentine subgroup. Owing to admixture, these varieties are not always easy to individualize, and distinctions are not usually made. There are three important mineral polymorphs of serpentine: antigorite, lizardite and chrysotile. Serpentine minerals are polymorphous, meaning that they have the same chemical formulae, but the atoms are arranged into different structures, or crystal lattices. Chrysotile, which has a fibrous habit, is one polymorph of serpentine and is one of the more important asbestos minerals. Other polymorphs in the serpentine subgroup may have a platy habit. Antigorite and lizardite are the polymorphs with platy habit. Many types of serpentine have been used for jewelry and hardstone carving, sometimes under the name "false jade" or "Teton jade". Most serpentines are opaque to translucent, light (specific gravity between 2.2 and 2.9), soft (hardness 2.5–4), infusible and susceptible to acids. All are microcrystalline and massive in habit, never being found as single crystals. Lustre may be vitreous, silky or greasy. Colors range from white to grey, yellow to green, and brown to black, and are often splotchy or veined. Many are intergrown with other minerals, such as calcite and dolomite. The basic structural unit of serpentine is a polar layer 0.72 nm thick. A Mg-rich trioctahedral sheet is tightly linked on one side to a single tetrahedral silicate sheet, regardless of the 3–5% larger lateral lattice dimensions of the octahedral sheet. The second level of the structure organized into different serpentine species originates partly to compensate the intra-layer stress due to this dimensional misfit. Good compensation results in a nearly constant layer curvature, with the larger octahedral sheet on the convex side. However, such curvature weakens the Serpentines find use in industry for several purposes, such as railway ballasts, building materials, and the asbestiform types find use as thermal and electrical insulation (chrysotile asbestos). The asbestos content can be released into the air when serpentine is excavated and if it is used as a road surface, forming a long-term health hazard by breathing. Asbestos from serpentine can also appear at low levels in water supplies through normal weathering processes, but there is as yet no fully proven health hazard associated with use or ingestion, although the EPA states an increased risk of developing benign intestinal polyps can occur. In its natural state, some forms of serpentine react with carbon dioxide and re-release oxygen into the atmosphere. The more attractive and durable varieties (all of the antigorite) are termed "noble" or "precious" serpentine and are used extensively as gems and in ornamental carvings. The town of Bhera in the historic Punjab province of the Indian subcontinent was known for centuries for finishing a relatively pure form of green serpentine obtained from quarries in Afghanistan into lapidary work, cups, ornamental sword hilts, and dagger handles. This high-grade serpentine ore was known as sang-i-yashm in Persian, or 'false jade' in English, and was used for generations by Indian craftsmen for lapidary work. It is easily carved, taking a good polish, and is said to have a pleasingly greasy feel. Less valuable serpentine ores of varying hardness and clarity are also sometimes dyed to imitate jade. Misleading synonyms for this material include "Suzhou jade", "Styrian jade", and "New jade". New Caledonian serpentine is particularly rich in nickel. The Māori of New Zealand once carved beautiful objects from local serpentine, which they called tangiwai, meaning "tears". The lapis atracius of the Romans, now known as verde antique, or verde antic, is a serpentinite breccia popular as a decorative facing stone. In classical times it was mined at Casambala, Thessaly, Greece. Serpentinite marbles are also widely used: Green Connemara marble (or 'Irish green marble') from Connemara, Ireland (and many other sources), and red Rosso di Levanto marble from Italy. Use is limited to indoor settings as serpentinites do not weather well.