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Item 182W and HSE constraints from 2.7 Ga komatiites on the heterogeneous nature of the Archen mantle(Elsevier, 2018-03-02) Puchtel, I.S.; Blichert-Toft, J.; Touboul, M.; Walker, Richard J.While the isotopically heterogeneous nature of the terrestrial mantle has long been established, the origin, scale, and longevity of the heterogeneities for different elements and isotopic systems are still debated. Here, we report Nd, Hf, W, and Os isotopic and highly siderophile element (HSE) abundance data for the Boston Creek komatiitic basalt lava flow (BCF) in the 2.7 Ga Abitibi greenstone belt, Canada. This lava flow is characterized by strong depletions in Al and heavy rare earth elements (REE), enrichments in light REE, and initial e143Nd = +2.5 ± 0.2 and initial e176Hf = +4.2 ± 0.9 indicative of derivation from a deep mantle source with time-integrated suprachondritic Sm/Nd and Lu/Hf ratios. The data plot on the terrestrial Nd-Hf array suggesting minimal involvement of early magma ocean processes in the fractionation of lithophile trace elements in the mantle source. This conclusion is supported by a mean mu142Nd = -3.8 ± 2.8 that is unresolvable from terrestrial standards. By contrast, the BCF exhibits a positive 182W anomaly (mu182W = +11.7 ± 4.5), yet is characterized by chondritic initial g187Os = +0.1 ± 0.3 and low inferred source HSE abundances (35 ± 5% of those estimated for the present-day Bulk Silicate Earth, BSE). Collectively, these characteristics are unique among Archean komatiite systems studied so far. The deficit in the HSE, coupled with the chondritic Os isotopic composition, but a positive 182W anomaly, are best explained by derivation of the parental BCF magma from a mantle domain characterized by a predominance of HSE-deficient, differentiated late accreted material. According to the model presented here, the mantle domain that gave rise to the BCF received only ~35% of the present-day HSE complement in the BSE before becoming isolated from the rest of the convecting mantle until the time of komatiite emplacement at 2.72 Ga. These new data provide strong evidence for a highly heterogeneous Archean mantle in terms of absolute HSE abundances and W isotopic composition, and also indicate slow mixing, on a timescale of at least 1.8 billion years. Additionally, the data are consistent with a stagnant-lid plate tectonic regime in the Hadean and Archean, prior to the onset of modern-style plate tectonics.Item Oceanic and continental lithospheric mantle in the 1.95 Ga Jormua Ophiolite Complex, Finland: implications for mantle and crustal evolution(Oxford, 2023-10-31) Finlayson, Valerie; Haller, Mitchell; Day, James M.D.; Ginley, Stephen; O'Driskoll, Brian; Kontinen, Asko; Hanski, Eero; Walker, Richard J.The ca. 1.95 Ga Jormua Ophiolite Complex (JOC), Finland, is a rare Paleoproterozoic ophiolite that preserves a record of diverse upper mantle materials and melting processes. Meter-scale grid sampling of four JOC outcrops, as well as non-grid samples, permits evaluation of meter- to kilometer-scale mantle heterogeneity within the JOC. Significant heterogeneity is observed between the four grids, and also among a number of the non-grid samples examined. Variations in the concentrations of fluid-mobile elements are particularly large among different samples and locations. New whole-rock major, lithophile trace, and highly siderophile element data (HSE: Os, Ir, Ru, Pt, Pd, Re), including 187Re-187Os isotopic data, for serpentinized harzburgites indicate the presence of two distinct compositional types and probable modes of origin within the JOC. This is consistent with prior findings. Type 1 is similar to modern refractory abyssal-type mantle. Type 2 is more highly refractory than Type 1, and most likely represents samples from sub-continental lithospheric mantle (SCLM). Type 1 mantle is moderately heterogeneous with respect to chemical and Os isotopic compositions at both the meter and kilometer scales. By contrast, Type 2 mantle is considerably more homogeneous than Type 1 grids at the meter scale, but is more heterogeneous at the kilometer scale. The median initial γOs value for Type 1 mantle, calculated for 1.95 Ga, is ~-2.0 (where γOs is the % deviation in 187Os/188Os relative to a chondritic reference calculated for a specified time). This isotopic composition is consistent with a moderate, long-term decrease in Re/Os relative to the estimate for Primitive Mantle, prior to JOC formation. The similarity in this γOs value to the value for the modern abyssal mantle, as well as the initial values for several Phanerozoic ophiolites suggests that the upper mantle achieved a Re/Os ratio similar to the chondritic reference by ~2 Ga, then evolved along a subparallel trajectory to the chondritic reference since then. For this to occur, only limited Re could have been permanently removed from the upper mantle since at least the time the JOC formed. A localized secondary metasomatic event at ~2 Ga, concurrent with the estimated obduction age for the JOC and subsequent Svecofennian Orogeny, affected the HSE systematics of some Type 1 samples. By contrast, late Archean Os TRD model ages for Type 2 rocks indicate a depletion event superimposed upon the long-term Re depletion of the abyssal mantle. This event was established no later than ~2.6 Ga and may have occurred during a period of significant, well-documented crustal production in the Karelia craton at ~2.7 Ga.Item In Search of Late-Stage Planetary Building Blocks(Elsevier, 2015-07-03) Walker, Richard J.; Bermingham, Katherine; Liu, Jingao; Puchtel, Igor S.; Touboul, Mathieu; Worsham, Emily A.Genetic contributions to the final stages of planetary growth, including materials associated with the giant Moon-forming impact, late accretion, and late heavy bombardment are examined using siderophile elements. Isotopic similarities between the Earth and Moon for both lithophile and siderophile elements collectively lead to the suggestion that the genetics of the building blocks for Earth, and the impactor involved in the Moon-forming event were broadly similar, and shared some strong genetic affinities with enstatite chondrites. The bulk genetic fingerprint of materials subsequently added to Earth by late accretion, defined as the addition of ~0.5 wt.% of Earth's mass to the mantle, following cessation of core formation, was characterized by 187Os/188Os and Pd/Ir ratios that were also similar to those in some enstatite chondrites. However, the integrated fingerprint of late accreted matter differs from enstatite chondrites in terms of the relative abundances of certain other HSE, most notably Ru/Ir. The final ≤0.05 wt.% addition of material to the Earth and Moon, believed by some to be part of a late heavy bombardment, included a component with much more fractionated relative HSE abundances than evidenced in the average late accretionary component. Heterogeneous 182W/184Wisotopic compositions of some ancient terrestrial rocks suggest that some very early formed mantle domains remained chemically distinct for long periods of time following primary planetary accretion. This evidence for sluggish mixing of the early mantle suggests that if late accretionary contributions to the mantle were genetically diverse, it may be possible to isotopically identify the disparate primordial components in the terrestrial rock record using the siderophile element tracers Ru and Mo.Item High-Precision Tungsten Isotopic Analysis by Multicollection Negative Thermal Ionization Mass Spectrometry Based on Simultaneous Measurement of W and 18O/16O Isotope Ratios for Accurate Fractionation Correction(American Chemical Society, 2016-01-11) Trinquier, Anne; Touboul, Mathieu; Walker, Richard J.Determination of the 182W/184W ratio to a precision of ±5 ppm (2σ) is desirable for constraining the timing of core formation and other early planetary differentiation processes. However, WO3 − analysis by negative thermal ionization mass spectrometry normally results in a residual correlation between the instrumental-mass-fractionation-corrected 182W/184W and 183W/184W ratios that is attributed to mass-dependent variability of O isotopes over the course of an analysis and between different analyses. A second-order correction using the 183W/184W ratio relies on the assumption that this ratio is constant in nature. This may prove invalid, as has already been realized for other isotope systems. The present study utilizes simultaneous monitoring of the 18O/16O and W isotope ratios to correct oxide interferences on a per-integration basis and thus avoid the need for a double normalization of W isotopes. After normalization of W isotope ratios to a pair of W isotopes, following the exponential law, no residual W−O isotope correlation is observed. However, there is a non-ideal mass bias residual correlation between 182W/iW and 183W/iW with time. Without double normalization of W isotopes and on the basis of three or four duplicate analyses, the external reproducibility per session of 182W/184W and 183W/184W normalized to 186W/183W is 5−6 ppm (2σ, 1−3 μg loads). The combined uncertainty per session is less than 4 ppm for 183W/184W and less than 6 ppm for 182W/184W (2σm) for loads between 3000 and 50 ng.Item Widespread tungsten isotope anomalies and W mobility in crustal and mantle rocks of the Eoarchean Saglek Block, northern Labrador, Canada: Implications for early Earth processes and W recycling(Elsevier, 2016-08-15) Liu, Jingao; Touboul, Mathieu; Ishikawa, Akira; Walker, Richard J.; Pearson, D. GrahamWell-resolved 182W isotope anomalies, relative to the present mantle, in Hadean–Archean terrestrial rocks have been interpreted to reflect the effects of variable late accretion and early mantle differentiation processes. To further explore these early Earth processes, we have carried out W concentration and isotopic measurements of Eoarchean ultramafic rocks, including lithospheric mantle rocks, metakomatiites, a layered ultramafic body and associated crustal gneisses and amphibolites from the Uivak gneiss terrane of the Saglek Block, northern Labrador, Canada. These analyses are augmented by in situ W concentration measurements of individual phases in order to examine the major hosts of W in these rocks. Although the W budget in some rocks can be largely explained by a combination of their major phases, W in other rocks is hosted mainly in secondary grain-boundary assemblages, as well as in cryptic, unidentified W-bearing ‘nugget’ minerals. Whole rock W concentrations in the ultramafic rocks show unexpected enrichments relative, to elements with similar incompatibilities. By contrast, W concentrations are low in the Uivak gneisses. These data, along with the in situ W concentration data, suggest metamorphic transport/re-distribution of W from the regional felsic rocks, the Uivak gneiss precursors, to the spatially associated ultramafic rocks. All but one sample from the lithologically varied Eoarchean Saglek suite is characterized by generally uniform ∼+11 ppm enrichments in 182W relative to Earth’s modern mantle. Modeling shows that the W isotopic enrichments in the ultramafic rocks were primarily inherited from the surrounding 182W-rich felsic precursor rocks, and that the W isotopic composition of the original ultramafic rocks cannot be determined. The observed W isotopic composition of mafic to ultramafic rocks in intimate contact with ancient crust should be viewed with caution in order to plate constraints on the early Hf–W isotopic evolution of the Earth’s mantle with regard to late accretionary processes. Although 182W anomalies can be erased via mixing in the convective mantle, recycling of 182W-rich crustal rocks into the mantle can produce new mantle sources with anomalous W isotopic compositions that can be tapped at much later times and, hence, this process should be considered as a mechanism for the generation of 182W-rich rocks at any subsequent time in Earth history.Item Age, genetics, and crystallization sequence of the group IIIE iron meteorites(Elsevier, 2023-06-14) Chiappe, Emily M.; Ash, Richard; Walker, Richard J.Chemical and isotopic data were obtained for ten iron meteorites classified as members of the IIIE group. Nine of the IIIE irons exhibit broadly similar bulk siderophile element characteristics. Modeling of highly siderophile element abundances suggests that they can be related to one another through simple crystal-liquid fractionation of a parent melt. Our preferred model suggests initial S, P, and C concentrations of approximately 12 wt%, 0.8 wt %, and 0.08 wt%, respectively. The modeled IIIE parent melt composition is ~4 times more enriched in highly siderophile elements than a non-carbonaceous (NC) chondrite-like parent body, suggesting a core comprising ~22% of the mass of the parent body. Although chemically distinct from the other IIIE irons, formation of the anomalous IIIE iron Aletai can potentially be accounted for under the conditions of this model through the nonequilibrium mixing of an evolved liquid and early formed solid. Cosmic ray exposure-corrected nucleosynthetic Mo, Ru, and W isotopic compositions of four of the bona fide IIIE irons and Aletai indicate that they originated from the non-carbonaceous (NC) isotopic domain. Tungsten-182 isotopic data for the IIIE irons and Aletai yield similar model metal-silicate segregation ages of 1.6 ± 0.8 Myr and 1.2 ± 0.8 Myr, respectively, after calcium aluminum-rich inclusion (CAI) formation. These ages are consistent with those reported for other NC-type iron meteorite parent bodies. The IIIE irons are chemically and isotopically similar to the much larger IIIAB group. Despite some textural, mineralogical, and chemical differences, such as higher C content, the new results suggest they may have originated from a different crystallization sequence on the same or closely-related parent body.Item Geodynamic implications of ophiolitic chromitites in the La Cabaña ultramafic bodies, Central Chile(Taylor & Francis, 2014-07-18) González-Jiménez, José María; Barra, Fernando; Walker, Richard J.; Reich, Martin; Gervilla, FernandoChromitites (>80% volume chromite) hosted in two ultramafic bodies (Lavanderos and Centinela Bajo) from the Palaeozoic metamorphic basement of the Chilean Coastal Cordillera were studied in terms of their chromite composition, platinum group element (PGE) abundances, and Re-Os isotopic systematics. Primary chromite (Cr# = 0.64–0.66; Mg# = 48.71–51.81) is only preserved in some massive chromitites from the Centinela Bajo ultramafic body. This chemical fingerprint is similar to other high-Cr chromitites from ophiolite complexes, suggesting that they crystallized from arc-type melt similar to high-Mg island-arc tholeiites (IAT) and boninites in supra-subduction mantle. The chromitites display enrichment in IPGE (Os, Ir, Ru) over PPGE (Rh, Pt, Pd), with PGE concentrations between 180 and 347 ppb, as is typical of chromitites hosted in the mantle of supra-subduction zone (SSZ) ophiolites. Laurite (RuS2)-erlichmanite (OsS2) phases are the most abundant inclusions of platinum-group minerals (PGM) in chromite, indicating crystallization from S-undersaturated melts in the subarc mantle. The metamorphism associated with the emplacement of the ultramafic bodies in the La Cabaña has been determined to be ca. 300 Ma, based on K-Ar dating of fuchsite. Initial 187Os/188Os ratios for four chromitite samples, calculated for this age, range from 0.1248 to 0.1271. These isotopic compositions are well within the range of chromitites hosted in the mantle section of other Phanaerozoic ophiolites. Collectively, these mineralogical and geochemical features are interpreted in terms of chromite crystallization in dunite channels beneath a spreading centre that opened a marginal basin above a supra-subduction zone. This implies that chromitite-bearing serpentinites in the metamorphic basement of the Coastal Cordillera are of oceanic-mantle origin and not oceanic crust as previously suggested. We suggest that old subcontinental mantle underlying the hypothetical Chilenia micro-continent was unroofed and later altered during the opening of the marginal basin. This defined the compositional and structural framework in which the protoliths of the meta-igneous and meta-sedimentary rocks of the Eastern and Western Series of the Chilean Coastal Cordillera basement were formed.Item Preservation of Earth-forming events in the W isotopic 1 composition of modern flood basalts(Science Magazine, 2016-05-13) Rizo, Hanika; Walker, Richard J.; Carlson, Richard W.; Horan, Mary F.; Mukhopadhyay, Sujoy; Manthos, Vicky; Francis, Don; Jackson, Matthew G.How much of Earth's compositional variation dates to processes that occurred during planet formation remains an unanswered question. High-precision tungsten isotopic data from rocks from two large igneous provinces, the North Atlantic Igneous Province and the Ontong Java Plateau, reveal preservation to the Phanerozoic of tungsten isotopic heterogeneities in the mantle. These heterogeneities, caused by the decay of hafnium-182 in mantle domains with high hafnium/tungsten ratios, were created during the first ~50 million years of solar system history, indicating that portions of the mantle that formed during Earth’s primary accretionary period have survived to the present.Item Rethinking marriage metabolism: The declining frequency of marital events in the United States(Population Research and Policy Review, 2023) Cohen, Philip N.Previous research has used the concept of marriage metabolism to represent churning in the marriage system, but the measurements used to date have been inadequate. This paper addresses changes in the incidence of marital events in the United States from 2008 to 2021. I offer a measure, the Total Rate of Marital Events (TRME), of the projected lifetime experience of marital transitions (marriage, divorce, and widowhood) for life table cohorts. I find that the TRME declined steeply over this relatively short period: 22% for men and 19% for women. All three components declined in every age group below 90. The decline in divorce was most pronounced. More accurately than the term "retreat from marriage," I describe the slowing churn of the marriage system as reflecting the diminished social presence of marriage in daily life. Rather than a retreat, this coincides with the increasingly selective status of married life. A higher status marriage system is a smaller, slower, and more stable marriage system.Item Growing Uncertainty in Marriage Expectations among U.S. Youth(Socius, 2024-03-26) Cohen, Philip N.; Pepin, Joanna R.Marriage rates are falling in the United States. The authors ask whether today's young adults are likely to continue this trend. Using Monitoring the Future Public-Use Cross-Sectional Datasets (1976-2022), this visualization presents U.S. 12th graders' marriage expectations. It shows declining optimism that they will be "very good" spouses and declining expectations that they will eventually marry. Both trends are prominent in the last 10 years of the survey, and both are more dramatic among young women than among young men. If these trends hold, it may foretell further declines in marriage rates in the coming years.Item Family Rejection and LGBTQ+ Asian Americans’ Psychological Distress and Disordered Eating: The Role of Conflicts in Allegiances and Familial Shame(2024) Pease, M V.; Le, Thomas P.; Ahn, Lydia HaRimLGBTQ+ Asian Americans experience unique psychological health concerns at the intersection of multiple forms of marginalization. White supremacist, cisheteronormative, and colonial ideals and their structural and interpersonal manifestations may encourage family rejection of LGBTQ+ identities within Asian American family units. Family shame, conflicts in allegiances, and internalized anti-LGBTQ+ stigma were hypothesized as mediators in the association between family rejection and psychological distress and disordered eating. The current study examined family rejection and its impacts on psychological distress and disordered eating in a sample of LGBTQ+ Asian American adults (N = 155; MAge = 24.26; 30.3% Gender Diverse) using a cross-sectional survey design and path analysis. There was a significant serial mediation such that family rejection was positively associated with conflicts in allegiances, which was positively associated with familial shame, which was positively associated with psychological distress (B = .12, p = .01). The same serial mediation was nonsignificant for disordered eating (B = .04, p = .26). Results indicate the importance of considering conflicts in allegiances, family shame, and the interpersonal dynamics of LGBTQ+ Asian Americans in understanding experiences of psychological distress and disordered eating. Implications are drawn for further research, clinical work, and broader efforts addressing the larger sociocultural environment that encourages familial rejection of LGBTQ+ identity.Item Talking Culture: Women in the production of community in the northwest Amazon(American Anthropologist, 2003) Chernela, JanetTaking the Northwest Amazon of Brazil as its example, this article argues for the analytic concept of a “speech culture,” combining, but heuristically separating, speech practice and language ideology. In the Northwest Amazon, an ideology of language establishes an equivalence between linguistic performance and descent group belonging. In contrast to the fixed, normative notions of groupness, this article explores the dynamic construction of social relations through women’s ritualized wept greeting speech. In these interactions, linguistic differentiation is countered by the experience of a single speech act based upon shared principles with organized participation in and by different linguistic codes. Through the collaborative nature of the speech act a common ground is produced and revealed. The community in this sense emerges as a cultural artifact whose production is largely the work of women. Through these speech interactions—of similar sentiments and meanings across different linguistic codes—women of the Northwest Amazon construct a community of talk.Item Disparities in Toxic Chemical Exposures and Associated Neurodevelopmental Outcomes: A Scoping Review and Systematic Evidence Map of the Epidemiological Literature(2023-09-27) Payne-Sturges, Devon C.; Taiwo, Tanya Khemet; Ellickson, Kristie; Mullen, Haley; Tchangalova, Nedelina ; Anderko, Laura ; Chen, Aimin ; Swanson, MaureenBACKGROUND: Children are routinely exposed to chemicals known or suspected of harming brain development. Targeting Environmental Neuro-Development Risks (Project TENDR), an alliance of more than 50 leading scientists, health professionals, and advocates, is working to protect children from these toxic chemicals and pollutants, especially the disproportionate exposures experienced by children from families with low incomes and families of color. OBJECTIVE: This scoping review was initiated to map existing literature on disparities in neurodevelopmental outcomes for U.S. children from population groups who have been historically economically/socially marginalized and exposed to seven exemplar neurotoxicants: combustion-related air pollution (AP), lead (Pb), mercury (Hg), organophosphate pesticides (OPs), phthalates (Phth), polybrominated diphenyl ethers (PBDEs), and polychlorinated biphenyls (PCBs). METHODS: Systematic literature searches for the seven exemplar chemicals, informed by the Population, Exposure, Comparator, Outcome (PECO) framework, were conducted through 18 November 2022, using PubMed, CINAHL Plus (EBSCO), GreenFILE (EBSCO), and Web of Science sources. We examined these studies regarding authors’ conceptualization and operationalization of race, ethnicity, and other indicators of sociodemographic and socioeconomic disadvantage; whether studies presented data on exposure and outcome disparities and the patterns of those disparities; and the evidence of effect modification by or interaction with race and ethnicity. RESULTS: Two hundred twelve individual studies met the search criteria and were reviewed, resulting in 218 studies or investigations being included in this review. AP and Pb were the most commonly studied exposures. The most frequently identified neurodevelopmental outcomes were cognitive and behavioral/psychological. Approximately a third (74 studies) reported investigations of interactions or effect modification with 69% (51 of 74 studies) reporting the presence of interactions or effect modification. However, less than half of the studies presented data on disparities in the outcome or the exposure, and fewer conducted formal tests of heterogeneity. Ninety-two percent of the 165 articles that examined race and ethnicity did not provide an explanation of their constructs for these variables, creating an incomplete picture. DISCUSSION: As a whole, the studies we reviewed indicated a complex story about how racial and ethnic minority and low-income children may be disproportionately harmed by exposures to neurotoxicants, and this has implications for targeting interventions, policy change, and other necessary investments to eliminate these health disparities. We provide recommendations on improving environmental epidemiological studies on environmental health disparities. To achieve environmental justice and health equity, we recommend concomitant strategies to eradicate both neurotoxic chemical exposures and systems that perpetuate social inequities.Item Anthracite Memories: Semantic Tagging and Coal Mining Oral Histories(2023) Paul A. ShackelOral histories are a critical source of information about lived experiences of past events. They have been analyzed both for their form – linguistically as texts, performances, and expressive accounts – and their content for understanding historic events and personal experiences. Here we focus on sentiment analysis approaches frequently applied to big data research questions, but less often utilized by anthropologists working with oral histories. Oral histories collected half a century ago in the anthracite mining communities of northeastern Pennsylvania are examined by considering methodological and historical questions. This project explores how oral history and data science might be productively combined to understand these now historic communities' everyday lives and working conditions. Bakhtin's (1981) concept of chronotope helps us understand the memory of these anthracite coal mining communities' daily life and working conditions.Item The PhotoDissociation Region Toolbox: Software and Models for Astrophysical Analysis(The Astronomical Journal, 2023-01-15) Pound, Marc W.; Wolfire, Mark G.The PhotoDissociation Region Toolbox provides comprehensive, easy-to-use, public software tools and models that enable an understanding of the interaction of the light of young, luminous, massive stars with the gas and dust in the Milky Way and in other galaxies. It consists of an open-source Python toolkit and photodissociation region (PDR) models for analysis of infrared and millimeter/submillimeter line and continuum observations obtained by ground-based and suborbital telescopes, and astrophysics space missions. PDRs include all of the neutral gas in the interstellar medium where far-ultraviolet photons dominate the chemistry and/or heating. In regions of massive star formation, PDRs are created at the boundaries between the H II regions and neutral molecular cloud, as photons with energies 6 eV < hν < 13.6 eV photodissociate molecules and photoionize metals. The gas is heated by photoelectrons from small grains and large molecules and cools mostly through far-infrared (FIR) fine-structure lines like [O I] and [C II]. The models are created from state-of-the art PDR codes that include molecular freezeout; recent collision, chemical, and photorates; new chemical pathways, such as oxygen chemistry; and allow for both clumpy and uniform media. The models predict the emergent intensities of many spectral lines and FIR continuum. The tools find the best-fit models to the observations and provide insight into the physical conditions and chemical makeup of the gas and dust. The PDR Toolbox enables novel analysis of data from telescopes such as the Infrared Space Observatory, Spitzer, Herschel, the Stratospheric Terahertz Observatory, the Stratospheric Observatory for Infrared Astronomy, the Submillimeter Wave Astronomy Satellite, the Atacama Pathfinder Experiment, the Atacama Large Millimeter/submillimeter Array, and the JWST.Item Black Sexual Minority Adults’ Avoidance of Professional Mental Health Care(Psychiatric Services, 2023) Williams, Natasha D.; Turpin, Rodman E.; Boekeloo, Bradley O.; King-Marshall, Evelyn C.; Fish, Jessica N.Objective: The authors sought to determine whether Black sexual minority individuals were more likely than White sexual minority individuals to postpone or avoid professional mental health care (PMHC) and, if so, to identify the reasons for postponing or avoiding care. Methods: Analyses were conducted with a subsample of cisgender Black (N=78) and White (N=398) sexual minority individuals from a larger survey of U.S. adults administered via MTurk in 2020 (N=1,012). Logistic regression models were used to identify racial differences in overall postponement or avoidance of care as well as differences in the prevalence of each of nine reasons for postponing or avoiding care. Results: Black sexual minority individuals were more likely than their White counterparts to report ever postponing or avoiding PMHC (average marginal effect [AME]=13.7 percentage points, 95% CI=5.4–21.9). Black sexual minority people also were more likely than their White counterparts to cite beliefs that they should work out their problems on their own (AME=13.1 percentage points, 95% CI=1.2–24.9) or with family and friends (AME=17.5 percentage points, 95% CI=6.0–29.1) and to cite providers’ refusal to treat them (AME=17.4 percentage points, 95% CI=7.6–27.1) as reasons for postponing or avoiding care. Conclusions: Black sexual minority individuals were more likely than their White counterparts to report delaying or avoiding PMHC. Personal beliefs about managing mental health and providers’ refusal to offer treatment influenced Black sexual minority individuals’ willingness or ability to seek PMHC.