Average sedimentary rock rare Earth element patterns and crustal evolution: Some observations and implications from the 3800 Ma ISUA supracrustal belt, West Greenland

Rare earth element (REE) data is given on a set of clastic metasediments from the 3800 Ma Isua Supracrustal belt, West Greenland. Each of two units from the same sedimentary sequence has a distinctive REE pattern, but the average of these rocks bears a very strong resemblance to the REE pattern for the North American Shale Composite (NASC), and departs considerably from previous estimates of REE patterns in Archaean sediments. The possibility that the source area for the Isua sediments resembled that of the NASC is regarded as highly unlikely. However, REE patterns like that in the NASC may be produced by sedimentary recycling of material yielding patterns such as are found at Isua. The results lead to the following tentative conclusions: (1) The REE patterns for Isua Seq. B MBG indicate the existence of crustal materials with fractionated REE and negative Eu anomalies at 3800 Ma, (2) The average Seq. B REE pattern resembles that of the North American Shale Composite (NASC), (3) If the Seq. B average is truly representative of its crustal sources, then this early crust could have been extensively differentiated. In this regard, a proper understanding of the NASC pattern, and its relationship to post-Archaean crustal REE reservoirs, is essential, (4) The Isua results may represent a local effect

The Hope Valley Shear Zone - A Major Late Paleozoic Ductile Shear Zone in Southeastern New England

Guidebook for field trips in Connecticut and adjacent areas of New York and Rhode Island: New England Intercollegiate Geological Conference 77th annual meeting, Yale University, New Haven, Connecticut, October 4-6, 1985: Trip B

Rare Earths Abundances and Fractionations and their Implications for Batholithic Petrogenesis in the Peninsular Ranges Batholith, California, USA, and Baja California, Mexico

Rare Earth Element (REE) patterns of plutonic rocks across the Peninsular Ranges batholith vary systematically west to east, transverse to the long axis and structural trends of the batholith. Three major parallel elongate geographic regions are each defined by distinct REE pattern types. Rocks from the western region display slight light REE enrichment, flat heavy REE, and negative Eu anomalies. An abrupt transition to rocks with middle and heavy REE fractionated and depleted REE patterns with no or positive Eu anomalies occurs in the central region of the batholith. Further to the east a second transition to strongly light REE enriched rocks some of which have positive or negative Eu anomalies occurs. Some gabbros may show divergent patterns. These large variations are observed even in similar lithologies across the three regions and notably in tonalites, the major rock type of the batholith. The slopes of the REE patterns within rocks of each region are largely independent of rock type, and no consistent variations in REE abundances and Eu anomalies with lithology are noted with the exception of some gabbros. Most of the leucogranodiorites of the western region have larger negative Eu anomalies than nearby tonalites. Granodioritic rocks of the central and eastern regions may have positive, negative, or no Eu anomalies. These results are the first report of systematic variations in REE characteristics across a granitic batholith whose geologic setting at a convergent plate boundary has been established. Some similarities and contrasts to REE variations across modern volcanic arcs are noted. Along the westernmost margin of the batholith in northern Baja California, Mexico, leucotonalitic rocks of the San Telmo pluton display essentially flat REE patterns strongly resembling those observed for near-trench volcanic rocks. The REE patterns of quartz gabbros and tonalites of the western region correspond closely to those of circum-Pacific high-alumina basalts. The heavy REE depleted and fractionated patterns observed in the rocks of the central and eastern regions of the batholith do not have counterparts in oceanic island volcanic arcs, and few counterparts in continental margin volcanic arcs. The REE variations generally correlate with other transverse asymmetries in major petrologic and geochemical characteristics. The abrupt depletion and fractionation in the middle to heavy REE and elimination of negative Eu anomalies appear coupled to an increase in Sr concentration and a marked restriction in lithologic diversity. This transition occurs over a range of initial 87Sr/86Sr ratios. The light REE enriched rocks of the eastern region are distinguished from the central and western regions by higher initial ratios. Geographic discontinuities in δ18O and age distributions in the batholith correlate approximately with the REE discontinuities, but locally diverge by the dimensions of one or two plutons. Determinations of REE abundances in major and trace phases of a representative eastern region granodiorite indicate accessory sphene and allanite are the major reservoirs of REE in this rock. Hornblende is the only significant REE site in the major minerals, and in some batholithic lithologies it may be the dominant site. High-level crystal fractionations involving hornblende and accessory phases do not appear capable of producing the observed geographic characteristics. Contamination processes including upper crustal material also seem ruled out. The REE and other geochemical variations across the batholith appear to originate in deep-seated sources. Partial melting in source rocks in which assemblages rich in plagioclase give way laterally to garnet-bearing assemblages in source regions of broadly basaltic composition which are already zoned in light REE abundances, 87Sr/86Sr, δ18O, and possibly Sr content appears to account for most of the observed features. The geologic context of the source material remains largely undefined and may include mantle and crustal components. However, the source regions for all parts of the batholith must have bulk compositions and phase assemblages capable of producing the dominant tonalite and low-K2O granodiorite lithologies. This major constraint appears to strongly limit the amount of sialic crustal material permitted to be present in the source regions. The geometry of the convergent boundary appears to have determined the elongate form of the batholith, and, probably, the general alignment of all the geochemical variations along its length. The results of this study may be useful in comparing possibly related crust-forming processes and products in other orogenic-plutonic terrains.</p

A 680,000-person megastudy of nudges to encourage vaccination in pharmacies

Encouraging vaccination is a pressing policy problem. To assess whether text-based reminders can encourage pharmacy vaccination and what kinds of messages work best, we conducted a megastudy. We randomly assigned 689,693 Walmart pharmacy patients to receive one of 22 different text reminders using a variety of different behavioral science principles to nudge flu vaccination or to a business-as-usual control condition that received no messages. We found that the reminder texts that we tested increased pharmacy vaccination rates by an average of 2.0 percentage points, or 6.8%, over a 3-mo follow-up period. The most-effective messages reminded patients that a flu shot was waiting for them and delivered reminders on multiple days. The top-performing intervention included two texts delivered 3 d apart and communicated to patients that a vaccine was “waiting for you.” Neither experts nor lay people anticipated that this would be the best-performing treatment, underscoring the value of simultaneously testing many different nudges in a highly powered megastudy

Impact of glacial activity on the weathering of Hf isotopes – Observations from Southwest Greenland

Data for the modern oceans and their authigenic precipitates suggest incongruent release of hafnium (Hf) isotopes by chemical weathering of the continents. The fact that weathering during recent glacial periods is associated with more congruent release of Hf isotopes has led to the hypothesis that the incongruency may be controlled by retention of unradiogenic Hf by zircons, and that glacial grinding enhances release of Hf from zircons. Here we study the relationship between glacial weathering processes and Hf isotope compositions released to rivers fed by land-terminating glaciers of the Greenland Ice Sheet, as well as neighbouring non-glacial streams. The weathered source rocks in the studied area mostly consist of gneisses, but also include amphibolites of the same age (1.9 Ga). Hafnium and neodymium isotope compositions in catchment sediments and in the riverine suspended load are consistent with a predominantly gneissic source containing variable trace amounts of zircon and different abundances of hornblende, garnet and titanite. Glacially sourced rivers and non-glacial streams fed by precipitation and lakes show very unradiogenic Nd isotopic compositions, in a narrow range (ɛNd = −42.8 to −37.9). Hafnium isotopes, on the other hand, are much more radiogenic and variable, with ɛHf between −18.3 and −0.9 in glacial rivers, and even more radiogenic values of +15.8 to +46.3 in non-glacial streams. Although relatively unradiogenic Hf is released by glacial weathering, glacial rivers actually fall close to the seawater array in Hf-Nd isotope space and are not distinctly unradiogenic. Based on their abundance in rocks and sediments and their isotope compositions, different minerals contribute to the radiogenic Hf in solution with a decreasing relevance from garnet to titanite, hornblende and apatite. Neodymium isotopes preclude a much stronger representation of titanite, hornblende and apatite in solution, such as might result from differences in dissolution rates, than estimated from mineral abundance. The strong contrast in Hf isotope compositions between glacial rivers and non-glacial streams results mostly from different contributions from garnet and zircon, where zircon weathering is more efficient in the subglacial environment. A key difference between glacial and non-glacial waters is the water-rock interaction time. While glacial rivers receive continuous contributions from long residence time waters of distributed subglacial drainage systems, non-glacial streams are characterized by fast superficial drainage above the permafrost horizon. Therefore, the increased congruency in Hf isotope weathering in glacial systems could simply reflect the hydrological conditions at the base of the ice-sheet and glaciers, with zircon weathering contributions increasing with water-rock interaction time

A 680,000-person megastudy of nudges to encourage vaccination in pharmacies

Encouraging vaccination is a pressing policy problem. To assess whether text-based reminders can encourage pharmacy vaccination and what kinds of messages work best, we conducted a megastudy. We randomly assigned 689,693 Walmart pharmacy patients to receive one of 22 different text reminders using a variety of different behavioral science principles to nudge flu vaccination or to a business-as-usual control condition that received no messages. We found that the reminder texts that we tested increased pharmacy vaccination rates by an average of 2.0 percentage points, or 6.8%, over a 3-mo follow-up period. The most-effective messages reminded patients that a flu shot was waiting for them and delivered reminders on multiple days. The top-performing intervention included two texts delivered 3 d apart and communicated to patients that a vaccine was “waiting for you.” Neither experts nor lay people anticipated that this would be the best-performing treatment, underscoring the value of simultaneously testing many different nudges in a highly powered megastudy.https://www.pnas.org/content/pnas/119/6/e2115126119.full.pd

Structural and Functional Hierarchy in Photosynthetic Energy Conversion—from Molecules to Nanostructures

Basic principles of structural and functional requirements of photosynthetic energy conversion in hierarchically organized machineries are reviewed. Blueprints of photosynthesis, the energetic basis of virtually all life on Earth, can serve the basis for constructing artificial light energy-converting molecular devices. In photosynthetic organisms, the conversion of light energy into chemical energy takes places in highly organized fine-tunable systems with structural and functional hierarchy. The incident photons are absorbed by light-harvesting complexes, which funnel the excitation energy into reaction centre (RC) protein complexes containing redox-active chlorophyll molecules; the primary charge separations in the RCs are followed by vectorial transport of charges (electrons and protons) in the photosynthetic membrane. RCs possess properties that make their use in solar energy-converting and integrated optoelectronic systems feasible. Therefore, there is a large interest in many laboratories and in the industry toward their use in molecular devices. RCs have been bound to different carrier matrices, with their photophysical and photochemical activities largely retained in the nano-systems and with electronic connection to conducting surfaces. We show examples of RCs bound to carbon-based materials (functionalized and non-functionalized single- and multiwalled carbon nanotubes), transitional metal oxides (ITO) and conducting polymers and porous silicon and characterize their photochemical activities. Recently, we adapted several physical and chemical methods for binding RCs to different nanomaterials. It is generally found that the P(+)(Q(A)Q(B))(−) charge pair, which is formed after single saturating light excitation is stabilized after the attachment of the RCs to the nanostructures, which is followed by slow reorganization of the protein structure. Measuring the electric conductivity in a direct contact mode or in electrochemical cell indicates that there is an electronic interaction between the protein and the inorganic carrier matrices. This can be a basis of sensing element of bio-hybrid device for biosensor and/or optoelectronic applications