Search

From a practical point of view, grain structure heterogeneities are key parameters that control the rock response and still remains a challenge to incorporate in a quantitative manner. One of the less discussed topics in the context of the grain-based model (GBM) in the particle flow code (PFC) is the contact heterogeneities and the appropriate contact model to mimic the grain boundary behavior. Generally, the smooth joint (SJ) model and linear parallel bond (LPB) model are used to simulate the grain boundary behavior. However, the literature does not document the suitability of different models for specific problems. Another challenge in implementing GBM in PFC is that only a single bonding parameter is used at the grain boundaries. The aim of this study is to investigate the responses of a laboratory-scale specimen with SJ and LPB models, considering grain boundary heterogeneous and homogeneous contact parameters. Uniaxial and biaxial compression tests are performed to calibrate the response of Creighton granite. The stress–strain curves, volumetric dilation, inter-crack (crack in the grain boundary), and intra-crack (crack within the grain) development, and failure patterns associated with different contact models are examined. It was found that both the SJ and LPB models can reproduce the pre-peak behavior observed for a granitic rock type. However, the LPB model is unable to reproduce the post-peak behavior. Due to the large interlocking effect originating from the balls in contact and the ball size in the LPB model, local dilation is induced at the grain boundaries. This overestimates the volumetric dilation and residual shear strength. The LPB model tends to result in discontinuous inter-cracks and stress localization in the rock specimen, resulting in fine fragments at the rock surface during failure.

In-situ tracer experiment is considered an effective means of understanding the migration characteristics of groundwater solutes under actual underground environments. The authors have developed tracer test equipment applicable to mainly fractured rock masses, and methods for evaluating experimental results. To confirm their usefulness, a tracer experiment was conducted for a single fracture in a granitic rock mass at the Mizunami Underground Research Laboratory. A numerical analysis was performed for the breakthrough curves obtained from the experiment. As a result, we were able to estimate the solute transport characteristics of the target fracture, including the aperture, the dispersion length, and the sorption coefficients of the sorbing tracers on the fracture surface and the rock matrix. Batch sorption tests were also conducted for rock samples collected at the test site. The differences between the sorption coefficients estimated from in-situ tracer tests and those obtained from batch tests were shown for Toki granite. [ABSTRACT FROM AUTHOR]

MX-80 bentonite colloids' effect on radionuclide sorption was studied by batch method and transport in flow using a granitic drill core column and Sr(II) as a radionuclide. Batch-type sorption and desorption experiments were conducted to determine Sr(II)'s distribution coefficients on bentonite colloids and metatexitic gneiss. Molecular modeling assessed the radionuclide's sorption affinity and justified the differences in Sr(II)'s sorption behavior on biotite versus montmorillonite. The distribution coefficients were found to be a hundred times greater for colloids than for granitic rock. Strontium's breakthrough from the column with bentonite colloids was successful without notable retardation on rock minerals. [ABSTRACT FROM AUTHOR]

In this paper, eight samples of different granitic rocks were selected from the Borujerd area in Lorestan Province, western Iran. Petrographic studies were performed, and some of their mineralogical indices [i.e., Feldspathic Index (IF), Colouration Index (IC), and Quartz-Feldspar Index (IQF)], and textural indices [i.e., Texture Coefficient (TC), Index of Interlocking (g), Index of Grain Size Homogeneity (t), and Index of Mean Grain Size (MGS)] were determined. Furthermore, the samples’ strength was measured by point load test. Afterward, the slake durability tests under dry conditions (i.e., without test solution), distilled water, and Na2SO4 solution were carried out for up to 120 cycles. Through these tests, the slake durability index (SDI) of the samples was determined every 20 cycles. The results revealed that the durability behavior is more influenced by their IQF, t, MGS, and strength than other mineralogical and textural indices. The SDI values obtained from slake durability tests under dry conditions and distilled water showed that the samples’ decay was significantly affected by the test specimens’ abrasion. In comparison, the wetting-drying cycles played a negligible role in the samples’ decay. Regression analyses revealed that samples’ SDI could be predicted using their IQF, t, MGS, and strength with different accuracy levels. Consequently, regression equations provide significant practical advantages for a rapid durability assessment of granitic rocks. Moreover, they save the long time necessary for performing slake durability tests. Highlights : • The mineralogical and textural indices and strength of different granitic rocks were determined. • The SDTs under dry conditions, distilled water, Na2SO4 solution were carried out. • The wetting–drying cycles played a slight role on the samples’ decay. • The slake durability behavior of the samples is more influenced by their IQF, t, MGS, and strength. • Regression Eqs. provide notable practical advantages for a rapid long-term slake durability. [ABSTRACT FROM AUTHOR]

A dual-support smoothed particle hydrodynamics (DS-SPH) method is developed to quantify explosion-generated crack densities within granitic rock masses in field-scale computational domains. In DS-SPH framework, coupled Eulerian total Lagrangian formulations, along with interface treatment between solid and inviscid fluid particles are fully considered. A new momentum equation formulation for interface treatment between inviscid fluids with various density ratios inside the blast borehole is also developed. The DS-SPH solutions are extended in such a way that decoupled explosions together with free surface and non-reflecting boundary conditions can be easily implemented. The three main deficiencies of conventional SPH (e.g., inconsistency, tensile instability, and hourglass mode) are removed in the stabilized DS-SPH method. In addition, GPU parallelization is adopted to accelerate the stabilized DS-SPH approach for higher efficiency. Then, the robustness of the developed DS-SPH solutions are verified by a number of theoretical and computational examples, and reproducing the full-scale blast field experiments. The developed DS-SPH solutions precisely reproduce the experimentally observed blast wave structures, and crack densities at several monitor locations. This is accomplished by addressing uncertainties in input parameters and enforcing various stabilization terms in DS-SPH formulations. Satisfactory speedup and acceptable scalability are also obtained, demonstrating that GPU-accelerated DS-SPH is a promising tool to speed up field scale particle-based simulations. [ABSTRACT FROM AUTHOR]

South-central Vietnam abundantly presents magmatic rocks with larger volumes of Cretaceous granitic rocks. In this study, zircon U-Pb geochronology of granite samples from the Deoca, Ankroet, and Dinhquan complexes in south-central Vietnam are utilized to investigate Cretaceous granitic magmatism. According to U-Pb analysis results, zircon ages of granitic rocks display the Deoca at ~113-92 Ma, the Ankroet at ~103-98 Ma, and the Dinhquan at ~97-113 Ma. The range of ages is narrow from 113 to 92 Ma, with most common ages date at ~100 Ma. Published data and our results display that Cretaceous granitic magmatism was active between ~87-118 Ma and most active at ~100 Ma in south-central Vietnam. Additionally, the Deoca and Dinhquan complexes show inherited ages in Triassic followed by Proterozoic and Carboniferous to Ordovician. The obtained ages indicate that Itype granitic rocks could be derived from melting of basement rocks. Our study suggests that I-type granitic rocks in south-central Vietnam were significantly intruded around 100 Ma. [ABSTRACT FROM AUTHOR]

Simultaneous determination of zircon U–Pb age and titanium concentration for a single analysis spot gives both the crystallization age and temperature. In laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analysis, it is challenging to quantitatively analyse a low level of titanium concentration. Two approaches were employed using a quadrupole mass spectrometer equipped with a collision/reaction cell (CRC). In the first approach, the MS/MS mass-shift mode with oxygen reaction gas provided reliable and consistent measurement of titanium as 48Ti16O+. In the second approach, the titanium concentration was determined quantitatively from the signal intensity of 49Ti in the non-gas mode (without the inflow of collision/reaction gas into the CRC). The methods were applied to zircon samples of the Kurobegawa granite (KRG), the Okueyama granite (OKG), the Toki granite (TKG), and the Tono plutonic complex (TCP). The biotite K–Ar geochronology were employed for rock samples of the KRG, OKG, and TPC (N = 3) of which the zircon crystals were analysed. The obtained titanium concentrations of the zircon crystals can lead to the crystallization temperatures through Ti-in-zircon geothermometer.

This study aimed to determine the current geological and engineering features of granite blocks used as riprap material in the construction of Gelingüllü Dam which is in use for nearly 20 years. The riprap layer is divided into four zones (A, B, C and D) from the lowest lake water level to dam crest by noting the durations underwater. Samples taken from the zones were investigated for petrographic, physical, chemical and mechanical characteristics. Schmidt hardness hammer experiments were completed on site for blocks in the zones. The shape features of the blocks were determined with the fractal dimension method. Physical weathering developed on sections close to the surface of blocks in zones A, B and C which were in contact with water. Compared to blocks in zone D, blocks in zones A, B and C had higher porosity, water absorption and Los Angeles abrasion loss values, with lower density, uniaxial compressive strength, Schmidt hardness rebound values and Vp values. The increased porosity of blocks from zones A, B and C was caused by greater effects of physical factors like wetting–drying and freeze–thaw affecting the blocks in these zones in contact with lake water. This increased the speed of fragmentation and weakening of the blocks. According to the results obtained in the study, it is understood that over nearly twenty years, the weathering processes affecting the riprap layer have caused changes to the physical and mechanical features of the rock blocks. [ABSTRACT FROM AUTHOR]

Highlights • Water influences magma differentiation trend to generate granitic rocks. • Residual melt fraction (F) is estimated by incompatible elements. • Rhyolite-MELTS modeling shows variation of SiO 2 versus F as a hygrometer. • This hygrometer is relatively insensitive to oxygen fugacity. • Archean TTGs show petrogenetic conditions of high water as arc rocks. Abstract Water influences the physics and chemistry of magmatic differentiation because it reduces the melting point, decreases melt viscosity, modifies phase equilibria, and controls how latent heat is released. Here, we explore how compositional trends of fractionating magmas can be used to evaluate the amount of water in the crystallizing system. Of interest is the role of water in generating silicic magmas such as granites and rhyolites. Water expands the crystallization window over which silicic melts are stable, such that granites are limited to small residual melt fractions (F < 0.2) under dry conditions but stable over a wider range of residual melt fractions (F < 0.6) at high water contents. Variations of SiO 2 versus F are relatively insensitive to oxygen fugacity and can be used as a hygrometer for granitoids, where F is estimated through relative enrichments in incompatible elements, such as Th and K. We also show that generation of granitoids in arc environments follow distinctly different Mg#-SiO 2 trends compared with anorogenic or intra-plate granites. We confirm that arc magmas differentiate at higher water contents and possibly higher oxygen fugacities than anorogenic/intra-plate magmas. Finally, Archean TTGs (tonalite, trondhjemite, and granodiorite) show similar Mg#-SiO 2 systematics as Phanerozoic arc-related granitoids, suggesting similar petrogenetic physical and chemical conditions. [ABSTRACT FROM AUTHOR]

Abstract In the present study neptunium(V) uptake by crystalline granitic rock (Kuru Grey granite) and the role of stable and mobile bentonite colloids (MX-80) on the migration of neptunium(V) was investigated. Two different experimental setups were utilized, batch-type experiments under stagnant conditions and column experiments under flowing water conditions. The uptake of 10−6 M neptunium(V) by 40 g/L crushed granite in 10 mM NaClO 4 was found to be pH-dependent, whereas neptunium(V) uptake by MX-80 bentonite colloids (0.08–0.8 g/L) was pH-independent up to a pH-value of approximately 11. Column experiments were conducted in the presence and absence of colloids at two pH values (pH = 8 and 10) and two flow rates (0.3 and 0.8 mL/h) in 10 mM NaClO 4. The injected neptunium(V) concentration was 2 × 10−4 M and the colloid concentration ranged from 0.08 to 0.32 g/L. The properties of the flow field in the columns were investigated with a conservative chloride tracer, at the same two flow rates of 0.8 and 0.3 mL/h. The resulting breakthrough curves were modeled using the analytical solution of advection–matrix diffusion equation. A tailing of neptunium(V) breakthrough curves in comparison to the conservative tracer was observed, which could be explained by a slightly higher retardation of neptunium(V) in the column caused by sorption on the granite. The sorption was in general lower at pH 8 than at pH 10. In addition, the tailing was almost identical in the absence and presence of MX-80 bentonite colloids, implying that the influence of colloids on the neptunium(V) mobility is almost negligible. Highlights • The influence of MX-80 bentonite colloids on Np(V) migration in granitic media was investigated. • Sorption of Np(V) on granite was found to be pH-dependent, while a pH-independent uptake by MX-80 colloids was observed. • Np(V) migration in the absence and presence of MX-80 bentonite colloids was investigated in granite drill core columns. • A clear influence of bentonite colloids on Np(V) breakthrough was not observed. • The breakthrough was modeled with the analytical solution of advection–matrix diffusion equation. [ABSTRACT FROM AUTHOR]

Abstract In order to address the causes of compositional variations of crust-derived granitic rocks in continental margin arc, we focused on the petrogenesis of Eocene granitic host rocks with enclosed MMEs, associated metagabbro, fine-grained quartz-diorite in Xima-Tongbiguan area, the Tengchong Block, which is a continental margin arc related to the subduction of Neo-Tethys. Both the Eocene granitic and mafic rocks are characterized by gradual increment in enriched compositions, such as K, Rb, Th, LREE, initial 87Sr/86Sr, ε Nd (t), and ε Hf (t), but decreasing Pb isotopic ratios from the west to the east of the Tengchong Block. Zircon U Pb age data of granitic host rocks, MMEs, metagabbro and fine-grained quartz-diorite reveal a similar age range of 55–50 Ma. The lithologies, zircon Hf compositions, geochemical and isotopic signatures of host granitic rocks show that the origin of these host rocks are mainly controlled by magma mixing between felsic and mafic magma. The products of the mafic magma are dominated by metagabbro, fine-grained quartz-diorite and MMEs enclosed in granitic rocks, which are all resulted from the reaction and mixture between different mafic magmatic products and felsic magma. The metagabbros could be the products of felsic magma mixing with early crystallized mafic magma, and the fine-grained quartz-diorites could be the products of felsic magma mixing with crystal-rich mafic magma, and the MMEs could be the products of felsic magma mixing with crystal-poor mafic magma or melt. The metagabbro has positive ε Hf (t) values of 1.8 to 10.9, which could provide the relative primitive Lu Hf isotopic compositions of mafic magma, indicating that the mafic magma is derived from a depleted mantle. The host granitic rocks have negative ε Nd (t) values of −5.2 to −6.5, indicating that the felsic magma is derived from partial melting of an ancient mafic lower crust. Furthermore, there are excess reactions after magma mixing between the mafic and felsic magma, such as multi-stage reactions between solidified MMEs and felsic magma, and the disaggregation of MMEs, finally resulting in the basification of felsic magma. Magma mixing is therefore the main mechanism of the formation of granitic rocks in the Tengchong Block. The compositional variation of intermediate to acid igneous rock in a continental margin arc is likely dominated by the characteristics of mafic magma because the intermediate to acid igneous rock is derived from mixing of crust-derived granitic and different mantle sources-derived mafic magma. Highlights • Eocene granitic and mafic rocks in Tengchong block are coeval at 55-50 Ma • Granitic and mafic rocks have similar compositional change and genetic correlation • Compositional change of granitic rock in continental arc is caused by magma mixing [ABSTRACT FROM AUTHOR]

We conducted a hydraulic fracturing (HF) experiment at a 500-m-level gallery in Mizunami Underground Research Laboratory in central Japan. We drilled a hole downward from the gallery floor and initially injected water at a flow rate of 10 mL/min in a section of 36 mm in diameter and 160 mm in length that was selected to avoid a pre-existing joint. The first breakdown (BD) occurred at 9.20 MPa, whereupon we increased the flow rate to 30 mL/min and induced a second BD in the form of "refracturing" at 9.79 MPa, larger than the first BD pressure. Acoustic emissions (AEs) monitored with 16 sensors in four boreholes located 1 m away from the HF hole exhibited two-dimensional distributions, which likely delineate a crack induced by the fracturing. Expansions of the regions in which AEs occurred were observed only immediately after the first and second BDs. Many AE events in other periods were distributed within the regions where AE events had already occurred. The initial motion polarities of P-waves indicate that tensile-dominant AE events occurred when the regions expanded and they were distributed primarily on the frontiers of the regions where AE events had already occurred. The experimental results suggest that increasing the injection flow rate is effective for generating new cracks in the refracturing, with the new crack expansions being induced by tensile fracturing. [ABSTRACT FROM AUTHOR]

S‐type granites are igneous rock types that are widespread in all continental crust. These granites play a key role in global weathering patterns and can be important economic ores of rare earth elements (REEs). This study provides insights into the geochemical and mineralogical signatures of REEs in S‐type granites and their derived soil profiles along a climosequence from dry to humid climates of Brazil. Mineralogical, petrographic, geochemical and soil analyses (physical and chemical) were used to evaluate the geochemistry of REEs in rock and soil samples. The granites were characterized as strongly peraluminous, being classified as typical S‐types. Both the granites and their derived soils contained high contents of REEs, with monazite and apatite being the major source of REEs. The high enrichment of light REEs (LRREs) in monazite and apatite explained the REE fractionation evidenced in the S‐type granites. The normalized REE distribution patterns for soil profiles along the climosequence revealed the fractionation between light and heavy REEs (HREEs). The ratio of La/YbN > 1 also confirmed the LREEs/HREEs fractionation. The mineralogical composition of the parent material and the clay minerals (kaolintes) seemed to govern the fractionation between LREEs and HREEs in these soils. Chemical index of alteration (CIA) values, REE fractionation and kaolinite proportions in soil profiles increased from dry to humid climates. These results suggest that the degree of weathering plays an important role in the type and volume of secondary minerals, as well as the REE fractionation. Among the phyllosilicates, kaolinite seems to be the most important adsorbent of light REE. The higher positive Eu anomalies with advanced weathering are explained by the breakdown of plagioclase. The weathering of monazite and apatite was the main reason for the slight negative Ce anomalies in the soil profiles. This study can be used to comprehend the geochemistry of REEs in other parts of the tropics underlain by S‐type granites. [ABSTRACT FROM AUTHOR]

New geochronological and isotopic geochemical data are given, which make it possible to recognize two types of granitic rocks on the eastern Chukchi Peninsula. Early Cretaceous Tkachen and Dolina granitic plutons with zircon ages (U-Pb SIMS) of 119-122 and 131-136 Ma are related to the first type. They cut through Devonian-Lower Carboniferous basement rocks and are overlain by the Aptian-Albian Etelkuyum Formation. Basal units of the latter contain fragments of granitic rocks. Late Cretaceous Provideniya and Rumilet granitic plutons, which contain zircons with ages of 94 and 85 Ma (U-Pb SIMS), respectively, belong to the second type. They cut through volcanic-sedimentary rocks of the Etelkuyum and Leurvaam formations pertaining to the Okhotsk-Chukotka Volcanic Belt. In petrographic and geochemical features, the Early Cretaceous granitic rocks of the Tkachen Pluton are commensurable with I-type granites, while Late Cretaceous granite of the Rumilet Pluton is comparable to A2-type granite. The Sr-Nd isotopic data provide evidence that from the Early Cretaceous Tkachen and Dolina plutons to the Late Cretaceous Provideniya and Rumilet plutons, the degree of crustal assimilation of suprasubduction mantle-derived melts increases up to partial melting of heterogeneous continental crust enriched in rubidium. An unconformity and various degrees of secondary alteration of volcanic-sedimentary rocks have been established in the Okhotsk-Chukotka Volcanic Belt, and this was apparently caused by transition of the tectonic setting from suprasubduction to a transform margin with local extension. [ABSTRACT FROM AUTHOR]

Early Palaeozoic granitoids in the South Qilian Belt, central China, record details of the tectonic evolution and crustal growth of the Qilian orogenic belt. Five representative granitoids from the western South Qilian Belt were sampled for zircon LA-ICPMS U-Pb dating, Lu-Hf isotopes, and whole-rock geochemical analyses. Zircon U-Pb dating of two porphyritic granodiorites and a porphyritic monzogranite yielded ages of 442.7 ± 3.5, 441.8 ± 4.3, and 435.4 ± 3.5 Ma, respectively. These granitoids exhibit a geochemical affinity to I-type granite, are metaluminous with a low aluminium saturation index (A/CNK = 0.75-1.15), have moderate Al2O3 and low MgO contents, high La/Yb and low Sr/Y ratios, and are depleted in Nb, Ta, P, and Ti, which suggests a subduction zone magmatic arc affinity, with mixing between a primary mantle-derived magma with lesser continental crustal material. The syenogranite and monzogranite from the South Qilian Belt, which yield U-Pb zircon ages of 440.4 ± 9.0 and 442.3 ± 1.2 Ma, respectively, have pronounced S-type geochemical affinities, are peraluminous with A/CNK values of 1.07-1.16, have relatively high SiO2, Al2O3, K2O, and Rb contents, low Y and Yb, low Sr/Y and La/Yb ratios, positive Th, U, and light Rare Earth Element (REE) anomalies, and depletions in Nb, Ta, Sr, and Ti. Their geochemical signature suggests derivation from partial melting of continental crust in a syn-collisional setting. The Hf isotopic data of zircons from the granitoids show a significant input of Paleoproterozoic crust in the crustal formation of the western South Qilian Belt in Palaeozoic. Compare the εHf(t) value of S-type granite with that of I-type granite, the former may have a comparatively homogeneous source. Together with regional evidence, it is proposed that a collisional event occurred between the South Qilian Belt and the Central Qilian Belt at ca. 442-435 Ma. [ABSTRACT FROM AUTHOR]

In-situ rock failures can result from stress changes due to pure loading and/or unloading. Understanding of the damage evolution behavior in brittle rocks during loading and unloading is imperative for the designs of rock structures. In this paper, we investigate the damage evolution characteristics of a granitic rock during loading and unloading after a series of triaxial experiments performed at different confining pressures. The axial stress—axial strain variations of the tested specimens revealed that the specimens undergoing unloading fail with a lower axial strain compared to the specimens failed purely by loading. Higher confining pressures were observed to exacerbate the difference. Volumetric strain versus axial strain curves indicated that the curves reverse the trend with the beginning of major damage of specimens. We suggest here a new form of equation to describe the secant modulus variation of brittle rocks against the axial stress for the unloading process. Failure mechanisms of tested specimens showed two distinct patterns, namely, specimens under pure loading failed with a single distinct shear fracture while for the unloading case specimens displayed multiple intersecting fractures. In addition, analysis of the evolution of dissipation and elastic energy during deformation of the specimens under loading and unloading conditions showed differentiable characteristics. Moreover, we evaluated the variations of two damage indices defined based on the energy dissipation and secant modulus evolution during deformation and observed that both of them satisfactorily distinguish key stages of damage evolution. [ABSTRACT FROM AUTHOR]

This paper presents a combined field measurement and finite element modeling analysis of the mullions occurring on the contact of two granitic rocks with different grain size in the Taili High-Strain Deformation Zone (THDZ), West Liaoning of North China. All of the field data are located in the plot zone of the modeling results. Numerical modeling results indicate that: (1) The inter-angle between the tangent lines cross the cusp point and the ratio R of amplitude and width of mullions are the most effective parameters to describe the geometric shape and evolution of mullions, as well as useful indicators of the rheology of rocks. (2) The competence contrast controls the growth rate of mullions under shortening. It determines the possible ratio R of final mullions. Moreover, decreasing of the cusp angle in high competence contrast materials is faster than that in low competence contrast model. (3) The initial disturbance is an essential factor for the generation of mullions. Those contacts with higher initial disturbance will develop into mullions more easily and have a high growth rate during the same shortening deformation regime. (4) The rheology and deformation behavior of the granitic rocks in the study area are primarily controlled by the grain sizes of quartz and feldspar. The effective viscosity ratio of biotite adamellite and granitic gneisses is about 0.01–0.5. The deformation mechanisms of these granitic rocks should be dominated by a grain-size-sensitive diffusion creep. [ABSTRACT FROM AUTHOR]

This study reports Mo isotopic compositions for fifty-two Palaeozoic granitic rocks with contrasting source affinities (A-, I- and S-type) from the Lachlan Fold Belt (LFB) and the New England Batholith (NEB), both in SE Australia, and three compositionally zoned plutons (Loch Doon, Criffell, and Fleet) located in the Southern Uplands of Scotland. The results show relatively large variations in δ 98 Mo for igneous rocks ranging from −1.73‰ to 0.59‰ with significant overlaps between different types. No relationships between δ 98 Mo and δ 18 O or ASI (Alumina Saturation Index) are observed, indicating that Mo isotopes do not clearly distinguish igneous vs. sedimentary source types. Instead, effects of igneous processes, source mixing, regional geology, as well as hydrothermal activity control the Mo isotope compositions in these granites. It is found that Mo is mainly accommodated in biotite and to a lesser extent in hornblende. Hornblende and Fe 3+ -rich minerals may preferentially incorporate light isotopes, as reflected by negative correlations between δ 98 Mo and K/Rb and [Fe 2 O 3 ]. There is a positive correlation between initial 87 Sr/ 86 Sr and δ 98 Mo in I-type granitic rocks, reflecting the admixing of material from isotopically distinct sources. Granitic rocks from Scotland and Australia display strikingly similar curvilinear trends in δ 98 Mo vs. initial 87 Sr/ 86 Sr despite the differing regional geology. Localized hydrothermal effects can result in low δ 98 Mo in granite, as seen in three samples from Loch Doon and Criffell which have anomalously light δ 98 Mo of <−1‰. Based on this study, an estimate of δ 98 Mo = 0.14 ± 0.07‰ (95% s.e.) for the Phanerozoic upper crust is proposed. This is slightly heavier than basalts indicating an isotopically light lower crust and/or a systematic change to the crust resulting from subduction of isotopically light dehydrated slab and/or pelagic sediment over time. [ABSTRACT FROM AUTHOR]