Kenneth J. Domanik

The Murray Springs Clovis site, Pleistocene extinction, and the question of extraterrestrial impact

Some of the evidence for the recent hypothesis of an extraterrestrial impact that caused late Pleistocene megafaunal extinctions [Firestone et al. (2007) Proc Natl Acad Sci USA 104:16016–16021] was based upon samples collected at Murray Springs, a Clovis archaeological site in southeastern Arizona. Here we describe sampling and analyses of magnetic separates from within, above, and below the lower Younger Dryas boundary (LYDB) black mat at Murray Springs, as well as radiation measurements from the LYDB at Murray Springs and two other well-stratified Clovis sites. The main magnetic fraction at Murray Springs is maghemite. Magnetic microspherules have terrestrial origins but also occur as cosmic dust particles. We failed to find iridium or radiation anomalies. The evidence for massive biomass burning at Murray Springs is addressed and found to be lacking. We could not substantiate some of the claims by Firestone and others, but our findings do not preclude a terminal Pleistocene cosmic event.

Petrography, stable isotope compositions, microRaman spectroscopy, and presolar components of Roberts Massif 04133: A reduced CV3 carbonaceous chondrite

Here, we report the mineralogy, petrography, C-N-O-stable isotope compositions, degree of disorder of organic matter, and abundances of presolar components of the chondrite Roberts Massif (RBT) 04133 using a coordinated, multitechnique approach. The results of this study are inconsistent with its initial classification as a Renazzo-like carbonaceous chondrite, and strongly support RBT 04133 being a brecciated, reduced petrologic type >3.3 Vigarano-like carbonaceous (CV) chondrite. RBT 04133 shows no evidence for aqueous alteration. However, it is mildly thermally altered (up to approximately 440 °C); which is apparent in its whole-rock C and N isotopic compositions, the degree of disorder of C in insoluble organic matter, low presolar grain abundances, minor element compositions of Fe,Ni metal, chromite compositions and morphologies, and the presence of unequilibrated silicates. Sulfides within type I chondrules from RBT 04133 appear to be pre-accretionary (i.e., did not form via aqueous alteration), providing further evidence that some sulfide minerals formed prior to accretion of the CV chondrite parent body. The thin section studied contains two reduced CV3 lithologies, one of which appears to be more thermally metamorphosed, indicating that RBT 04133, like several other CV chondrites, is a breccia and thus experienced impact processing. Linear foliation of chondrules was not observed implying that RBT 04133 did not experience high velocity impacts that could lead to extensive thermal metamorphism. Presolar silicates are still present in RBT 04133, although presolar SiC grain abundances are very low, indicating that the progressive destruction or modification of presolar SiC grains begins before presolar silicate grains are completely unidentifiable.

Waimirite-(Y), orthorhombic YF3, a new mineral from the Pitinga mine, Presidente Figueiredo, Amazonas, Brazil and from Jabal Tawlah, Saudi Arabia: description and crystal structure

Abstract Waimirite-(Y) (IMA 2013-108), orthorhombic YF3, occurs associated with halloysite, in hydrothermal veins (up to 30 mm thick) cross-cutting the albite-enriched facies of the A-type Madeira granite (~1820 Ma), at the Pitinga mine, Presidente Figueiredo Co., Amazonas State, Brazil. Minerals in the granite are ‘K-feldspar’, albite, quartz, riebeckite, ‘biotite’, muscovite, cryolite, zircon, polylithionite, cassiterite, pyrochlore-group minerals, ‘columbite’, thorite, native lead, hematite, galena, fluorite, xenotime-(Y), gagarinite-(Y), fluocerite-(Ce), genthelvite–helvite, topaz, ‘illite’, kaolinite and ‘chlorite’. The mineral occurs as massive aggregates of platy crystals up to ~1 μm in size. Forms are not determined, but synthetic YF3 displays pinacoids, prisms and bipyramids. Colour: pale pink. Streak: white. Lustre: non-metallic. Transparent to translucent. Density (calc.) = 5.586 g/cm3 using the empirical formula. Waimirite-(Y) is biaxial, mean n = 1.54-1.56. The chemical composition is (average of 24 wavelength dispersive spectroscopy mode electron microprobe analyses, O calculated for charge balance): F 29.27, Ca 0.83, Y 37.25, La 0.19, Ce 0.30, Pr 0.15, Nd 0.65, Sm 0.74, Gd 1.86, Tb 0.78, Dy 8.06, Ho 1.85, Er 6.38, Tm 1.00, Yb 5.52, Lu 0.65, O (2.05), total (97.53) wt.%. The empirical formula (based on 1 cation) is (Y0.69Dy0.08Er0.06Yb0.05Ca0.03Gd0.02Ho0.02Nd0.01Sm0.01Tb0.01Tm0.01Lu0.01)∑1.00[F2.54⃞0.25O0.21]∑3.00. Orthorhombic, Pnma, a = 6.386(1), b = 6.877(1), c = 4.401(1) Å, V = 193.28(7) Å3, Z = 4 (powder data). Powder X-ray diffraction (XRD) data [d in Å (I) (hkl)]: 3.707 (26) (011), 3.623 (78) (101), 3.438 (99) (020), 3.205 (100) (111), 2.894 (59) (210), 1.937 (33) (131), 1.916 (24) (301), 1.862 (27) (230). The name is for the Waimiri-Atroari Indian people of Roraima and Amazonas. A second occurrence of waimirite-(Y) is described from the hydrothermally altered quartz-rich microgranite at Jabal Tawlah, Saudi Arabia. Electron microprobe analyses gave the empirical formula (Y0.79Dy0.08Er0.05Gd0.03Ho0.02Tb0.01 Tm0.01Yb0.01)∑1.00[F2.85O0.08⃞0.07]∑3.00. The crystal structure was determined with a single crystal from Saudi Arabia. Unit-cell parameters refined from single-crystal XRD data are a = 6.38270(12), b = 6.86727(12), c = 4.39168(8) Å, V = 192.495(6) Å3, Z = 4. The refinement converged to R1 = 0.0173 and wR2 = 0.0388 for 193 independent reflections. Waimirite-(Y) is isomorphous with synthetic SmF3, HoF3 and YbF3. The Y atom forms a 9-coordinated YF9 tricapped trigonal prism in the crystal structure. The substitution of Y for Dy, as well as for other lanthanoids, causes no notable deviations in the crystallographic values, such as unit-cell parameters and interatomic distances, from those of pure YF3.

Ecosystem Composition Controls the Fate of Rare Earth Elements during Incipient Soil Genesis

The rare earth elements (REE) are increasingly important in a variety of science and economic fields, including (bio)geosciences, paleoecology, astrobiology, and mining. However, REE distribution in early rock-microbe-plant systems has remained elusive. We tested the hypothesis that REE mass-partitioning during incipient weathering of basalt, rhyolite, granite and schist depends on the activity of microbes, vascular plants (Buffalo grass), and arbuscular mycorrhiza. Pore-water element abundances revealed a rapid transition from abiotic to biotic signatures of weathering, the latter associated with smaller aqueous loss and larger plant uptake. Abiotic dissolution was 39% of total denudation in plant-microbes-mycorrhiza treatment. Microbes incremented denudation, particularly in rhyolite, and this resulted in decreased bioavailable solid pools in this rock. Total mobilization (aqueous + uptake) was ten times greater in planted compared to abiotic treatments, REE masses in plant generally exceeding those in water. Larger plants increased bioavailable solid pools, consistent with enhanced soil genesis. Mycorrhiza generally had a positive effect on total mobilization. The main mechanism behind incipient REE weathering was carbonation enhanced by biotic respiration, the denudation patterns being largely dictated by mineralogy. A consistent biotic signature was observed in La:phosphate and mobilization: solid pool ratios, and in the pattern of denudation and uptake.

The crystal structure of bartelkeite, with a revised chemical formula, PbFeGeVI(Ge2IVO7)(OH)2·H2O, isotypic with high-pressure P21/m lawsonite

Abstract Bartelkeite from Tsumeb, Namibia, was originally described by Keller et al. (1981) with the chemical formula PbFeGe3O8. By means of electron microprobe analysis, single-crystal X-ray diffraction, and Raman spectroscopy, we examined this mineral from the type locality. Our results show that bartelkeite is monoclinic with space group P21/m, unit-cell parameters a = 5.8279(2), b = 13.6150(4), c = 6.3097(2) Å, β = 127.314(2)°, and a revised ideal chemical formula PbFeGeVIGe2IVO7(OH)2·H2O (Z = 2). Most remarkably, bartelkeite is isostructural with the high-pressure P21/m phase of lawsonite, CaAl2Si2O7(OH)·H2O, which is only stable above 8.6 GPa and a potential host for H2O in subducting slabs. Its structure consists of single chains of edge-sharing FeO6 and Ge1O6 octahedra parallel to the c-axis, cross-linked by Ge22O7 tetrahedral dimers. The average bond lengths for the GeO6 and GeO4 polyhedra are 1.889 and 1.744 Å, respectively. The Pb atoms and H2O groups occupy large cavities within the framework. The hydrogen bonding scheme in bartelkeite is similar to that in lawsonite. Bartelkeite represents the first known mineral containing both 4- and 6-coordinated Ge atoms and may serve as an excellent analog for further exploration of the temperature-pressure-composition space of lawsonite.

Agardite-(Y), Cu2+6Y(AsO4)3(OH)6·3H2O

Agardite-(Y), with a refined formula of Cu2+ 5.70(Y0.69Ca0.31)[(As0.83P0.17)O4]3(OH)6·3H2O [ideally Cu2+ 6Y(AsO4)3(OH)6·3H2O, hexacopper(II) yttrium tris(arsenate) hexahydroxide trihydrate], belongs to the mixite mineral group which is characterized by the general formula Cu2+ 6 A(TO4)3(OH)6·3H2O, where nine-coordinated cations in the A-site include rare earth elements along with Al, Ca, Pb, or Bi, and the T-site contains P or As. This study presents the first structure determination of agardite-(Y). It is based on the single-crystal X-ray diffraction of a natural sample from Jote West mine, Pampa Larga Mining District, Copiapo, Chile. The general structural feature of agardite-(Y) is characterized by infinite chains of edge-sharing CuO5 square pyramids (site symmetry 1) extending down the c axis, connected in the ab plane by edge-sharing YO9 polyhedra (site symmetry -6..) and corner-sharing AsO4 tetrahedra (site symmetry m..). Hydroxyl groups occupy each corner of the CuO5-square pyramids not shared by a neighboring As or Y atom. Each YO9 polyhedron is surrounded by three tubular channels. The walls of the channels, parallel to the c axis, are six-membered hexagonal rings comprised of CuO5 and AsO4 polyhedra in a 2:1 ratio, and contain free molecules of lattice water.

Paleoproterozoic orogenesis and quartz-arenite deposition in the Little Chino Valley area, Yavapai tectonic province, central Arizona, USA

New field mapping and laboratory studies of Paleoproterozoic rock units around Little Chino Valley in central Arizona clarify the timing of magmatism, deformation, and sedimentation in part of the Yavapai tectonic province and yield new insights into sources of sands and weathering environments. Mafic lavas, calc-silicate rocks, and pelitic and psammitic strata in the Jerome Canyon area west of Little Chino Valley were deposited, deformed, and intruded by the 1736 ± 21 (2σ) Ma Williamson Valley Granodiorite. U-Pb geochronologic analysis of detrital zircons from a sample of psammitic strata yielded a maximum depositional age of ca. 1738 Ma. Approximately 25% of the detrital-zircon grains were derived from a ca. 2480 Ma source, as previously identified in Grand Canyon schist units. Kolmogorov-Smirnov statistical comparison of the Jerome Canyon detrital-zircon analyses with Grand Canyon schist analyses indicates that three of the 12 samples analyzed by Shufeldt et al. (2010) are statistically indistinguishable from the Jerome Canyon sample at the 95% confidence level and supports the concept that the Jerome Canyon sequence and Paleoproterozoic schists in the eastern and western Grand Canyon are part of the same tectonostratigraphic terrane. The Del Rio Quartzite on the northeast side of Little Chino Valley, previously considered an outlier of Mazatzal Quartzite, consists of poorly sorted quartz arenite, pebbly quartz arenite, and conglomerate deposited in a braided-stream environment. Microscope examination of 32 thin sections stained for potassium and calcium failed to identify any feldspar, mica, or mafic silicate grains. Similarly, conglomerate clasts consist entirely of vein quartz and less abundant argillite and jasper. A rock unit interpreted as a paleosol beneath the Del Rio Quartzite contains no surviving minerals except quartz, some of which is embayed and rounded as in corrosive saprolitic soils. U-Pb geochronologic analyses of detrital zircons from the 1400-m-thick Quartzite indicate maximum depositional ages of ca. 1745 Ma for the base and ca. 1737 Ma for the top. The unit is folded but is unaffected by the penetrative deformation and metamorphism that affected other Paleoproterozoic volcanic and sedimentary strata in the area, and it is probably significantly younger. We infer that the physically immature but chemically super-mature Del Rio Quartzite was deposited during a time of extreme weathering during a hot, humid climate with exceptionally high atmospheric CO 2 concentrations and associated corrosive rainwater rich in carbonic acid.

Pirquitasite, Ag(2)ZnSnS(4).

Pirquitasite, ideally Ag2ZnSnS4 (disilver zinc tin tetrasulfide), exhibits tetragonal symmetry and is a member of the stannite group that has the general formula A2BCX 4, with A = Ag, Cu; B = Zn, Cd, Fe, Cu, Hg; C = Sn, Ge, Sb, As; and X = S, Se. In this study, single-crystal X-ray diffraction data are used to determine the structure of pirquitasite from a twinned crystal from the type locality, the Pirquitas deposit, Jujuy Province, Argentina, with anisotropic displacement parameters for all atoms, and a measured composition of (Ag1.87Cu0.13)(Zn0.61Fe0.36Cd0.03)SnS4. One Ag atom is located on Wyckoff site Wyckoff 2a (symmetry -4..), the other Ag atom is statistically disordered with minor amounts of Cu and is located on 2c (-4..), the (Zn, Fe, Cd) site on 2d (-4..), Sn on 2b (-4..), and S on general site 8g. This is the first determination of the crystal structure of pirquitasite, and our data indicate that the space group of pirquitasite is I-4, rather than I-42m as previously suggested. The structure was refined under consideration of twinning by inversion [twin ratio of the components 0.91 (6):0.09 (6)].

Lanthanite-(Nd), Nd2(CO3)3·8H2O.

Lanthanite-(Nd), ideally Nd2(CO3)3·8H2O [dineodymium(III) tricarbonate octahydrate], is a member of the lanthanite mineral group characterized by the general formula REE 2(CO3)3·8H2O, where REE is a 10-coordinated rare earth element. Based on single-crystal X-ray diffraction of a natural sample from Mitsukoshi, Hizen-cho, Karatsu City, Saga Prefecture, Japan, this study presents the first structure determination of lanthanite-(Nd). Its structure is very similar to that of other members of the lanthanite group. It is composed of infinite sheets made up of corner- and edge-sharing of two NdO10-polyhedra (both with site symmetry ..2) and two carbonate triangles (site symmetries ..2 and 1) parallel to the ab plane, and stacked perpendicular to c. These layers are linked to one another only through hydrogen bonding involving the water molecules.

Nioboaeschynite-(Ce), Ce(NbTi)O6

Nioboaeschynite-(Ce), ideally Ce(NbTi)O6 [cerium(III) niobium(V) titanium(IV) hexaoxide; refined formula of the natural sample is Ca0.25Ce0.79(Nb1.14Ti0.86)O6], belongs to the aeschynite mineral group which is characterized by the general formula AB 2(O,OH)6, where eight-coordinated A is a rare earth element, Ca, Th or Fe, and six-coordinated B is Ti, Nb, Ta or W. The general structural feature of nioboaeschynite-(Ce) resembles that of the other members of the aeschynite group. It is characterized by edge-sharing dimers of [(Nb,Ti)O6] octahedra which share corners to form a three-dimensional framework, with the A sites located in channels parallel to the b axis. The average A—O and B—O bond lengths in nioboaeschynite-(Ce) are 2.471 and 1.993 Å, respectively. Moreover, another eight-coordinated site, designated as the C site, is also located in the channels and is partially occupied by A-type cations. Additionally, the refinement revealed a splitting of the A site, with Ca displaced slightly from Ce (0.266 Å apart), presumably resulting from the crystal-chemical differences between the Ce3+ and Ca2+ cations.