Freeze Core Sampling to Validate Time‐Lapse Resistivity Monitoring of the Hyporheic Zone

A freeze core sampler was used to characterize hyporheic zone storage during a stream tracer test. The pore water from the frozen core showed tracer lingered in the hyporheic zone after the tracer had returned to background concentration in collocated well samples. These results confirmed evidence of lingering subsurface tracer seen in time‐lapse electrical resistivity tomographs. The pore water exhibited brine exclusion (ion concentrations in ice lower than source water) in a sediment matrix, despite the fast freezing time. Although freeze core sampling provided qualitative evidence of lingering tracer, it proved difficult to quantify tracer concentration because the amount of brine exclusion during freezing could not be accurately determined. Nonetheless, the additional evidence for lingering tracer supports using time‐lapse resistivity to detect regions of low fluid mobility within the hyporheic zone that can act as chemically reactive zones of importance in stream health.     

Genetic improvement of New Zealand aquaculture species: programmes,progress and prospects

Aquaculture, like terrestrial farming, cannot achieve economic and sustainable production without high performing genetic stocks tailored to the conditions under which they are grown. It is essential, therefore, that aquaculture investment includes genetics and biotechnology to adapt marine livestock to the novel conditions of intensive aquaculture and to the demanding markets into which they are sold. The return on investment in well-structured breeding programmes can be very high, and significant performance and economic gains have been demonstrated in multiple species. Many factors must be considered in designing a genetic improvement programme, including the reproductive biology of the species and the identification of realistic and commercially relevant breeding goals based on the resources and facilities available. This paper reviews the options available to aquaculturists and provides examples of how these are being applied to six aquaculture species in New Zealand: king salmon, hāpuku, kingfish, Greenshell^TM mussels, Pacific oysters and pāua (abalone).     

Observing lingering hyporheic storage using electrical resistivity: variations around stream restoration structures,Crabby Creek,PA

Time‐lapse geophysical surveys can map lingering hyporheic storage by detecting changes in response to saline tracer. Tracer tests were conducted in Crabby Creek, an urban stream outside Philadelphia, to examine the influence of stream restoration structures and variable sediment thickness. We compared electrical resistivity surveys with extensive well sampling (57 wells) in two 13.5‐m‐long reaches, each with a step drop created by a J‐hook. The two step drops varied in tracer behaviour, based on both the well data and the geophysical data. The well data showed more variation in arrival time where the streambed sediment was thick and was more uniform where sediment was thin. The resistivity in the reach with thin sediment showed lingering tracer in the hyporheic zone both upstream and downstream from the J‐hook. In the second reach where the sediment was thicker, the lingering tracer in the hyporheic zone was more extensive downstream from the J‐hook. The contrasting results between the two reaches from both methods suggested that sediments influenced hyporheic exchange more than the step at this location. Resistivity inversion differed from well data in both reaches in that it showed evidence for tracer after well samples had returned to background, mapping lingering tracer either upstream or downstream of a step. We conclude that resistivity surveys may become an important tool for hyporheic zone characterization because they provide information on the extent of slow moving fluids in the hyporheic zone, which have the potential to enhance chemical reactions. Copyright © 2012 John Wiley & Sons, Ltd.     

Feldspathic clasts in Yamato-86032: Remnants of the lunar crust with implications for its formation and impact history

Low concentrations of Th and Fe in the Yamato (Y)-86032 bulk meteorite support earlier suggestions that Y-86032 comes from a region of the moon far distant from the Procellarum KREEP Terrain (PKT), probably from the lunar farside. ³⁹Ar–⁴⁰Ar, Rb–Sr, Sm–Nd, and Sm-isotopic studies characterize the chronology of Y-86032 and its precursors in the mega regolith. One of the rock types present in a light gray breccia lithology is an anorthosite characterized by plagioclase with An 93, i.e., more sodic than lunar FANs, but with very low ⁸⁷Rb/⁸⁶Sr and ⁸⁷Sr/⁸⁶Sr similar to those of FANs. (FAN stands for Ferroan Anorthosite). This “An93 anorthosite” has Nd-isotopic systematics similar to those of nearside norites. A FAN-like “An97 anorthosite” is present in a second light-colored feldspathic breccia clast and has a more negative ε_Nd value consistent with residence in a LREE-enriched environment as would be provided by an early plagioclase flotation crust on the Lunar Magma Ocean (LMO). This result contrasts with generally positive values of ε_Nd for Apollo 16 FANs suggesting the possibility of assymetric development of the LMO. Other possible explanations for the dichotomy in ε_Nd values are advanced in the text. The Y-86032 protolith formed at least 4.43 ± 0.03 Ga ago as determined from a Sm–Nd isochron for mineral fragments from the breccia clast composed predominantly of An93 anorthosite and a second clast of more varied composition. We interpret the mineral fragments as being predominatly from a cogenetic rock suite. An ³⁹Ar–⁴⁰Ar age of 4.36–4.41 ± 0.035 Ga for a third clast composed predominantly of An97 anorthosite supports an old age for the protolith. Initial ¹⁴³Nd/¹⁴⁴Nd in that clast was −0.64 ± 0.13 ε-units below ¹⁴³Nd/¹⁴⁴Nd in reservoirs having chondritic Sm/Nd ratios, consistent with prior fractionation of mafic cumulates from the LMO. A maximum in the ³⁹Ar–⁴⁰Ar age spectrum of 4.23 ± 0.03 Ga for a second sample of the same feldspathic breccia clast probably reflects some diffusive ⁴⁰Ar loss. Lack of solar wind and lunar atmosphere implanted Ar in the light gray breccia clast allows determination of an ³⁹Ar/⁴⁰Ar age of 4.10 ± 0.02 Ga, which is interpreted as the time of initial brecciation of this litholgy. After correction for implanted lunar atmosphere ⁴⁰Ar, impact melt and dark regolith clasts give Ar ages of 3.8 ± 0.1 Ga implying melt formation and final breccia assembly 3.8 Ga ago. Some breccia lithologies were exposed to thermal neutron fluences of 2 × 10¹⁵ n/cm², only about 1% of the fluence experienced by some other lunar highlands meteorites. Other lithologies experienced neutron fluences of 1 × 10¹⁵ n/cm². Thus, Y-86032 spent most of the time following final brecciation deeply buried in the megaregolith. The neutron fluence data are consistent with cosmogenic ³⁸Ar_cos cosmic ray exposure ages of 10 Ma. Variations among differing lithologies in the amount of several regolith exposure indicators, including cosmogenic noble gas abundances, neutron capture induced variations in Sm isotopic abundances, and Ir contents, are consistent with a period of early (>3.8 Ga ago) lunar regolith exposure, subsequent deep burial at >5 m depth, and ejection from the moon 7–10 Ma ago.     

北山柳园地区中志留世埃达克质花岗岩类及其地质意义

北山柳园地区发育的埃达克质片麻状花岗闪长岩为钙碱性岩浆系列,具有较高SiO₂ (>56%),Al₂O₃ (>15%)和较低的MgO (<3%)含量,Na₂O>K₂O; 并且具有高的Sr含量(>400×10^-6)和Sr/Y比值; 样品轻重稀土强烈分异(La/Yb)_N ＝18~86,强烈亏损重稀土Yb与Y,具有不明显的Eu异常(δEu＝0.90~0.95); 富集LREE和大离子亲石元素(LILE),而亏损HREE、高场强元素(HFSE: Nb、Ta),与世界上典型的俯冲洋壳熔融形成的埃达克岩相似。然而样品具有相对高的(⁸⁷Sr/⁸⁶Sr)_I (0.70635~0.70636)和相对低的ε_Nd(t) (-0.8~-0.9),以及锆石具有相对较低的ε_Hf (t) (-0.8~+2.7)同位素特征,比典型的俯冲洋壳熔融形成埃达克岩具有更多的放射成因,推测可能是源区加入了地壳物质/沉积物/或特殊的洋壳(OIB/E-MORB)熔融,以及侵位过程中地壳物质的混染所造成的。埃达克质片麻状黑云母花岗岩锆石LA-ICPMS年龄为424±4Ma,代表了花岗岩埃达克花岗岩的结晶年龄。花牛山岛弧带在中晚志留世时期具有较高的地热梯度,发育了大面积高ε_Nd(t)钙碱性花岗岩和区域围岩发生了高温变质作用。因此,柳园埃达克岩是由于热的洋壳向花牛山岛弧地体俯冲过程中熔融形成的,俯冲洋壳熔融是本地区早古生代大规模地壳增生的重要方式之一。     

Chronology and petrogenesis of a 1.8 g lunar granitic clast:14321,1062

A study was undertaken to determine the chronology of a pristine granite clast (1062) from Apollo 14 breccia 14321 using Rb-Sr, Sm-Nd and ³⁹Ar-⁴⁰Ar methods. The genesis of the granite as constrained by the isotopic results and trace element characteristics is discussed.Chronology: The Rb-Sr internal isochron is slightly disturbed and yields an age of 4.09 ± 0.11 AE ($\text{λ(}{}^{87}\text{Rb) = 0.0139}\text{AE}{}^{\mathrm{?1}}$) and an imprecise initial I(Sr) = 0.702 ? .008. If two data are excluded, the age becomes 4.13 ± 0.03 AE and I(Sr) = 0.698 ? .003. The whole rock and mineral separates are extremely radiogenic; they yield model ages which are relatively well-defined. The average model age is 4.12 ± 0.03 AE (relative to BABI = 0.69898). The Sm-Nd internal isochron is also slightly disturbed and gives an age of 4.11 ± 0.20 AE ($\text{λ(}{}^{147}\text{Sm) = 0.00654}\text{AE}$^?1). The ³⁹Ar-⁴⁰Ar average age of the non-magnetic fraction of the sample yields a slightly younger age of 3.88 ± 0.03 AE (K-Ar constants from Steiger and $\text{>a}\text{?}$, 1977). The concordancy of Rb-Sr and Sm-Nd internal isochrons with the Rb-Sr model age strongly suggests that the granitic clast formed at 4.1 AE ago in the shallow crust and was later excavated and brecciated about 3.88 AE ago.Petrogenesis: Isotopic and trace element data of the lunar granite show large K/La and Rb/Sr fractionations, small Sm/Nd fractionation and the distinct V-shaped REE distribution pattern at the time of crystallization. A two-stage model involving crystal fractionation followed by silicate liquid immiscibility (SLI) is proposed for lunar granite genesis. We propose that the granite can be the immiscible acidic liquid produced by SLI from a residual liquid which underwent fractionation of ca, 3% of phases with REE distribution coefficients similar to those of phosphate minerals from a highly evolved parental magma with REE contents about twice those of the 15405,85 quartz monzodiorite (QMD).The extreme scarcity of lunar granitic samples and their young formation ages suggest that they are probably not directly crystallized from the differentiation of the primordial magma ocean. Our isotopic results and trace elements data from other workers suggest that granites, QMD and probably Mggabbronorites may be genetically related and may have formed in a plutonic environment similar to gabbro-granophyre associations in terrestrial layered intrusions such as the Skaergaard Intrusions.     

Trapped solar and cosmogenic noble gas abundances in Apollo 15 and 16 deep drill samples

Abundances and isotopic compositions of all the stable noble gases have been measured in 19 different depths of the Apollo 15 deep drill core, 7 different depths of the Apollo 16 deep drill core, and in several surface fines and breccias. All samples analyzed from both drill cores contain large concentrations of solar wind implanted gases, which demonstrates that even the deepest layers of both cores have experienced a lunar surface history. For the Apollo 15 core samples, trapped⁴He concentrations are constant to within a factor of two; elemental ratios show even greater similarities with mean values of⁴He/²²Ne= 683±44,²²Ne/³⁶Ar= 0.439±0.057,³⁶Ar/⁸⁴Kr= 1.60±0.11·10³, and⁸⁴Kr/¹³²Xe= 5.92±0.74. Apollo 16 core samples show distinctly lower⁴He contents,⁴He/²²Ne(567±74), and²²Ne/³⁶Ar(0.229±0.024), but their heavy-element ratios are essentially identical to Apollo 15 core samples. Apollo 16 surface fines also show lower values of⁴He/²²Ne and²²Ne/³⁶Ar. This phenomenon is attributed to greater fractionation during gas loss because of the higher plagioclase contents of Apollo 16 fines. Of these four elemental ratios as measured in both cores, only the²²Ne/³⁶Ar for the Apollo 15 core shows an apparent depth dependance. No unambiguous evidence was seen in these core materials of appreciable variations in the composition of the solar wind. Calculated concentrations of cosmic ray-produced²¹Ne,⁸⁰Kr, and¹²⁶Xe for the Apollo 15 core showed nearly flat (within a factor of two) depth profiles, but with smaller random concentration variations over depths of a few cm. These data are not consistent with a short-term core accretion model from non-irradiated regolith. The Apollo 15 core data are consistent with a combined accretion plus static time of a few hundred million years, and also indicate variable pre-accretion irradiation of core material. The lack of large variations in solar wind gas contents across core layers is also consistent with appreciable pre-accretion irradiation. Depth profiles of cosmogenic gases in the Apollo 16 core show considerably larger concentrations of cosmogenic gases below ～65 cm depth than above. This pattern may be interpreted either as an accretionary process, or by a more recent deposition of regolith to the upper ～70 cm of the core. Cosmogenic gas concentrations of several Apollo 16 fines and breccias are consistent with ages of North Ray Crater and South Ray Crater of ～50·10⁶ and ～2·10⁶ yr, respectively.     

He,Ne and Ar in chondritic NiFe as irradiation hardness sensors

Noble gas analyses of the Ni-Fe of 9 L, 5 H and 2 LL chondrites quantitatively support previous suggestions of radiogenic ⁴He recoil and ³He deficits. Furthermore, noble gases in the Ni-Fe show evidence for in situ produced radiogenic ⁴He and in some cases for recoil loss of ³⁸Ar and gain of ²¹Ne.The ratio of spallogenic ²¹Ne and ³⁸Ar in the metal phase is found to correlate strongly with ³He/²¹Ne and ²²Ne/²¹Ne in bulk samples of these chondrites. This is proof of the dependence of these ratios on the irradiation hardness experienced by the meteoroid in space. ‘Hardness indices’ n = 1.9–2.2 are found, indicating that on the average the stone meteoroids from which the samples came were smaller in mass than iron meteoroids. The spallogenic ²¹Ne/³⁸Ar ratio in metallic Ni-Fe can be used with the semi-empirical production model deduced from the Grant iron meteorite to calibrate spallogenic ³He/²¹Ne and ⁴Ne/²¹Ne in bulk samples of L, LL and H chondrites for meteoroid size and sample location allowing the estimation of minimal meteoroid masses. ³He and ²¹Ne production rates calculated from previously determined ³⁶Ar/³⁸Ar exposure ages for four L chondrites indicate that they are probably not single-valued functions of the ³He/²¹Ne ratio. The ratio of ³He in bulk samples to ³⁸Ar in metal samples of the same meteorite is constant (= 20 ± 3) whereas the ratio of ²¹Ne in the bulk to ³⁸Ar in the metal varies by as much as a factor of two in correlation with ³He/²¹Ne.     

Sm–Nd and Rb–Sr studies of lherzolitic shergottite Yamato 984028

The distribution pattern of the trace elements Rb, Sr, Nd and Sm for Yamato 984028 (Y984028) is consistent with its classification as a lherzolitic shergottite. The Sm–Nd mineral isochron of this lherzolitic shergottite defines its age to be 170 ± 10 Ma for an initial ?_Nd = +11.6 ± 0.2. The corresponding Rb–Sr mineral isochron yields an identical age of 170 ± 9 Ma and an initial ⁸⁷Sr/⁸⁶Sr = 0.710389 ± 0.000029. The concordant Sm–Nd and Rb–Sr isochron ages suggest that Y984028 crystallized 170 ± 7 Ma ago contemporaneously with five other lherzolitic shergottites and ten enriched basaltic and olivine-phyric shergottites. The age, Sr- and Nd- isotopic signatures further suggest that Y984028 and Y-793605, and also probably Y000097 could come from a single magmatic body. Using a two-stage evolution model, the time-averaged ⁸⁷Rb/⁸⁶Sr-ratio for the mantle source of the parent magma of Y984028 is ～0.182, within the range of 0.178–0.182 that has been reported for other lherzolitic shergottites. The corresponding time-averaged ¹⁴⁷Sm/¹⁴⁴Nd-ratio for the source mantle of its parent magma is super-chondritic at ～0.217, implying its source was a depleted mafic part of the Martian mantle similar to that of diabasic shergottite Northwest Africa (NWA) 1460. Rb, Sr, Sm and Nd distributions in Y984028 are likely produced by pyroxene and olivine accumulation, probably from a NWA 1460-like parental melt, in an intrusive magma body.