Robert M. Holder's research while affiliated with University of Michigan and other places

... However, the initial Pb isotopic composition of RD1 (Fig. 4A-D) is more radiogenic than that predicted for bulk terrestrial Pb during the Middle Cambrian to Middle Ordovician 42 . It is possible that this is due to locally oxygenated conditions that favoured the incorporation of 238 U during dolomitization (which decays to 206 Pb, thus decreasing 207 Pb/ 206 Pb) 43 , but such an interpretation would discount the large volume of geochemical evidence in favour of a reduced, hydrothermal fluid that had interacted with the underlying basement rocks 23,25 . In the latter case, fluid-rock interaction could give rise to the leaching of Pb from stratigraphically older, U-bearing minerals, resulting in lower than expected 207 Pb/ 206 Pb 35 . ...

... Therefore, we investigate these relationships within the Mojave region in the southern Basin and Range, testing the coupling between landscape history and species richness and composition across a hierarchy of spatial scales. As the longest subregional fossil record of the Basin and Range (26), evaluation of the Mojave region allows us to continuously sample at a subregional scale, reducing the potential for estimates of turnover to be confounded by spatial variation in the fossil record of the western US across temporal intervals (27,28). ...

... The presence of a paired positive Ce anomaly and a negative Eu anomaly is often observed in zircons of magmatic origin. Positive Ce anomalies are associated with high oxygen fugacity in the system, while negative Eu anomalies are associated with simultaneous crystallization of plagioclase in the melt [33,34]. Furthermore, the cores of zircon grains from granitic gneisses are characterized by increased contents of certain elements, including P (272-1014 ppm), Y (1168-9591 ppm), and Li (0.24-13.4 ppm). ...

... -accessed on 25 February 2024). In contrast, fluid availability and nature as well as the nature of the tectonic stress field are other aspects to view metamorphism [8,9]. These categories almost automatically determine the main approaches metamorphic geology follow. ...

... As shown in Fig. 3a, there is substantial variability in the stability fields depending on the choice of mineral composition and laboratory experiment, yet Fig. 3b demonstrates that the range of P-T paths at C3 overlap significantly with the hydrous mineral stability fields from experiments. Given the uncertainties associated with the thermal structure and slab geometry 40 , the precise position of C3, the variabilities in bulk-rock composition and fluid-content effects on dehydration 37,41 and the simplifications regarding the reaction kinetics 42 , it is plausible that C3 is due to fluids derived from dehydration in the forearc slab mantle. This is only possible if fluids reached depths of >15 km, otherwise forearc P-T conditions in the Shumagin segment are probably too cold and serpentinite would remain stable until arc or backarc depths. ...

... Similar clockwise P-T evolution paths are postulated for UHT metamorphism in Antarctica (Elvevold et al., 2020;Harley, 1998bHarley, , 2003Kawakami & Motoyoshi, 2004;Kelsey et al., 2007;Takamura et al., 2020) and Madagascar (e.g. Holder et al., 2018;Horton et al., 2021;Jöns & Schenk, 2011) as well. Our data from the semipelites and charnockites of F I G U R E 1 5 Compilation of P-T evolution paths from the Madurai Block (Raith et al., 1997 [1]; Sajeev et al., 2006 [2]; Santosh & Sajeev, 2006 [3]; Tsunogae & Santosh, 2006 [4], Tsunogae & Santosh, 2011 [7]; Braun et al., 2007 [5]; Tadokoro et al., 2007 [6]; Tsunogae et al., 2008 [8]; Raith et al., 2010 [9]; Brandt et al., 2011 [10]; Clark et al., 2015 [11]; Prakash et al., 2017 [12]; Li et al., 2020 [13]; Tiwari & Sarkar, 2020 [14]; Ray et al., 2021 [15]), this study, the Trivandrum Block (Chacko et al., 1987 [1]; Nandakumar & Harley, 2000 [2]; Cenki et al., 2002 [3]; Ishii et al., 2006 [4]; Tadokoro et al., 2008 [5]) and Sri Lanka (Perera, 1984(Perera, , 1994; Kriegsman, 1995 [7]; Kriegsman & Schumacher, 1999 [8]; Sajeev & Osanai, 2004 [2]; Sajeev et al., 2007 [3]; Dharmapriya et al., 2015 [1], Dharmapriya et al., 2015 [6], Dharmapriya et al., 2017 [4]; Takamura et al., 2015 [5]). ...

... Alternatively, we cannot rule out the possibility that oxygen and Pb isotope systems have responded to two separate late-stage alteration events. For example, oxygen and clumped isotopes were altered in dolomite samples during contact metamorphism around the Alta Stock (Utah, USA), while the U-Pb dates were not 31 . ...

... The oceanic record is more robust in the northern Appalachians and Caledonides, where well-exposed ophiolites (obducted oceanic crust) with near-complete lithospheric sections (e.g., the Bay of Islands and Betts Cove ophiolites, Canada, and the Solund-Stavfjord ophiolite, Norway) preserve a record of subduction zone processes in the Iapetus Ocean (Bédard, 1999;De Souza et al., 2008;Furnes et al., 1988;Olive et al., 1997;Oliver and McAlpine, 1998). In contrast, the southern Appalachians have a paucity of complete ophiolites, with oceanic rocks instead forming smaller complexes of mafic and ultramafic rocks (Crowley, 1976;Drake and Morgan, 1981;Guice et al., 2021;McElhaney and McSween, 1983;Misra and Conte, 1991;Mittwede, 1989;Tenthorey et al., 1996;Raymond et al., 2003Raymond et al., , 2016Peterson and Ryan, 2009;Spell and Norrell, 1990). The differences between the northern and southern sections of the Appalachian-Caledonian orogen have long been recognized, and studies have sought to correlate major events in the orogen's history using ophiolites and mafic-ultramafic complexes as markers for suture zones between terranes and continents (Hibbard et al., 2007, and references therein). ...

... The chondrite-normalized REE patterns of monazites in both sample ZY-LGT-1 (Tg) and ZY-LG-2 (2mg) are enriched in LREE relative to HREE (Fig. 12a, b) with marked Eu anomalies, which change through time in sample ZY-LGT-1. The negative Eu anomaly suggests co-crystallization of monazite with feldspar during melt crystallization (Holder et al., 2020), where Eu favorably partitions into feldspar. The monazite Eu anomaly could also reflect changes in oxygen fugacity of the system (Holder et al., 2020). ...

... It can be attributed to the metamorphic conditions of the underlying micaschist represented by an assemblage of garnet-staurolite + sillimanite for which conditions of 600°C at 5 kbar were calculated (Košuličová and Štípská, 2007). The mean grain size of 1200 μm retrieved from the M1m microstructure corresponds roughly to the grain size of the dynamically recrystallized marbles deformed at 600°C in the schists of the Svratka dome to the south of the studied area (Ulrich et al., 2020;Štípská et al., 2020). Therefore, the calcite grain size of approximately 1200 μm can be considered as being representative for the deformation temperature at around 600°C (Ulrich et al., 2006). ...