40Ar/39Ar Evidence For 1.4 Ga Regional Metamorphism in New Mexico: Implications For Thermal Evolution of Lithosphere in the Southwestern Usa

1997 ◽  
Vol 105 (2) ◽  
pp. 205-224 ◽  
Author(s):  
K. E. Karlstrom ◽  
R. D. Dallmeyer ◽  
J. A. Grambling
Keyword(s):  
New Mexico ◽  
Thermal Evolution ◽  
Regional Metamorphism ◽  
Southwestern Usa

Use of pyrite microfabric as a key to tectono-thermal evolution of massive sulphide deposits – an example from Deri, southern Rajasthan, India

1998 ◽  
Vol 62 (2) ◽  
pp. 197-212 ◽  
Author(s):  
Anju Tiwary ◽  
Mihir Deb ◽  
Nigel J. Cook
Keyword(s):  
Thermal Evolution ◽  
Regional Metamorphism ◽  
Massive Sulphide ◽  
Ductile Deformation ◽  
Sulphide Deposit ◽  
Fine Grained ◽  
Thermal Metamorphism ◽  
Sulphide Ores ◽  
History Of ◽  
South Delhi Fold Belt

AbstractPyrite is an ubiquitous constituent of the Proterozoic massive sulphide deposit at Deri, in the South Delhi Fold Belt of southern Rajasthan. Preserved pyrite microfabrics in the Zn-Pb-Cu sulphide ores of Deri reveal a polyphase growth history of the iron sulphide and enable the tectono-thermal evolution of the deposit to be reconstructed.Primary sedimentary features in Deri pyrites are preserved as compositional banding. Regional metamorphism from mid-greenschist to low amphibolite facies is recorded by various microtextures of pyrite. Trails of fine grained pyrite inclusions within hornblende porphyroblasts define S1-schistosity. Pyrite boudins aligned parallel to S1 mark the brittle–ductile transformation of pyrite during the earliest deformation in the region. Isoclinal to tight folds (F1 and F2) in pyrite layers relate to a ductile deformation stage during progressive regional metamorphism. Peak metamorphic conditions around 550°C, an estimation supported by garnet–biotite thermometry, resulted in annealing of pyrite grains, while porphyroblastic growth of pyrite (up to 900 µm) took place along the retrogressive path. Brittle deformation of pyrite and growth of irregular pyritic mass around such fractured porphyroblasts characterize the waning phase of regional metamorphism. A subsequent phase of stress-free, thermal metamorphism is recorded in the decussate and rosette textures of arsenopyrite prisms replacing irregular pyritic mass. Annealing of such patchy pyrite provides information regarding the temperature conditions during this episode of thermal metamorphism which is consistent with the hornblendehornfels facies metamorphism interpreted from magnetite–ilmenite geothermometry (550°C) and sphalerite geobarometry (3.5 kbar). A mild cataclastic deformation during the penultimate phase produced microfaults in twinned arsenopyrite prisms.

Low-pressure regional metamorphism in the Pyrenees and its implications for the thermal evolution of rifted continental crust

1987 ◽  
Vol 321 (1557) ◽  
pp. 219-242 ◽  
Keyword(s):  
Large Scale ◽  
Thermal Evolution ◽  
Tectonic Setting ◽  
Regional Metamorphism ◽  
Low Pressure ◽  
Maximum Temperature ◽  
Thermal Gradients ◽  
Temperature Heat ◽  
Isotope Studies ◽  
Strike Slip Movement

During late Palaeozoic (Hercynian) low-pressure regional metamorphism in the Pyrenees, exceptionally high thermal gradients existed within the upper crust, and temperatures as high as 700 °C were attained at depths as shallow as 10 km, resulting in large-scale crustal anatexis. Stable isotope studies indicate that the crust was flushed by circulating ground waters to depths of 12 km, but the amount of fluid involved below 8 km was probably not much greater than 50% of the rock mass, and this fluid apparently did not penetrate the pre-Palaeozoic basement below 12 km. There is no evidence for continental collision in the region at that time, and these data, together with other geological and geophysical constraints, suggest that the most plausible tectonic setting for the metamorphism is a zone of continental rifting, possibly associated with strike-slip movement. Thermal modelling suggests that a transient, high-temperature heat source in the lower crust is required to account for the observed metamorphic P - T arrays. Among a range of possible solutions, a basaltic sill, 6-8 km thick and emplaced at 14 km could generate a maximum temperature array similar to those observed in the Pyrenees.

Effect of predation on adult pronghorn Antilocapra americana (Antilocapridae) in New Mexico, Southwestern USA

Mammalia ◽  
2019 ◽  
Vol 83 (3) ◽  
pp. 248-254 ◽  
Author(s):  
Louis C. Bender ◽  
Octavio C. Rosas-Rosas ◽  
Matthew J. Hartsough ◽  
Cristina L. Rodden ◽  
Patrick C. Morrow
Keyword(s):  
New Mexico ◽  
Survival Rates ◽  
Nutritional Condition ◽  
Arid Environments ◽  
Antilocapra Americana ◽  
Southwestern Usa ◽  
The Mean ◽  
Southwest Usa ◽  
Two Populations ◽  
Predation Rates

Abstract The effect of predation on ungulate populations remains contentious, despite a lack of evidence showing impacts in arid Southwestern USA populations where low precipitation and frequent drought limit ungulate nutritional condition. These conditions can increase predisposition of prey to mortality, which is prerequisite for predation to be compensatory. Consequently, we tested the effect of predation on adult pronghorn Antilocapra americana (Ord 1815) in two populations in arid New Mexico by modeling transformed annual survival rates as a function of predation rates. For this conservative test, a slope=0 indicates complete compensation, whereas a slope=−1 indicates complete additivity. The corrected slope of mortality potentially attributable to predation was >−0.14, and this result was consistent among individual populations. Thus, predation was primarily compensatory. Primarily compensatory predation was related to the relatively low condition of pronghorn individuals, as predated individuals were all below the mean condition of the population, similar to results seen in previous tests of the compensatory versus additive predation hypothesis in the arid Southwest USA. Conditions that predispose individual ungulates to mortality are present more often than not in arid environments, and thus managers should not assume that predation is limiting, regardless of predation rates.

scholarly journals Zircon (U-Th)/He Thermochronologic Constraints on the Long-Term Thermal Evolution of Southern New Mexico and Western Texas

Lithosphere ◽  
2020 ◽  
Vol 2020 (1) ◽  
pp. 1-25
Author(s):  
Nathan Z. Reade ◽  
Julian M. Biddle ◽  
Jason W. Ricketts ◽  
Jeffrey M. Amato
Keyword(s):  
New Mexico ◽  
Elevated Temperatures ◽  
Thermal Evolution ◽  
Near Surface ◽  
Tectonic History ◽  
Inverse Models ◽  
Final Development ◽  
Thermal Histories ◽  
Lower Temperature ◽  
Forward And Inverse Modeling

Abstract Zircon (U-Th)/He (ZHe) dates are presented from eight samples (n=55) collected from three ranges including the Carrizo and Franklin Mountains in western Texas and the Cookes Range in southern New Mexico. ZHe dates from Proterozoic crystalline rocks range from 6 to 731 Ma in the Carrizo Mountains, 19 to 401 Ma in the Franklin Mountains, and 63 to 446 Ma in the Cookes Range, and there is a negative correlation with eU values. These locations have experienced a complex tectonic history involving multiple periods of uplift and reburial, and we use a combination of forward and inverse modeling approaches to constrain plausible thermal histories. Our final inverse models span hundreds of millions of years and multiple tectonic events and lead to the following conclusions: (1) Proterozoic exhumation occurred from 800 to 500 Ma, coinciding with the break-up of Rodinia; (2) elevated temperatures at approximately 100 Ma occurred during final development of the Bisbee basin and are a likely result of elevated heat flow in the upper crust during continental rifting; (3) a pulse of cooling associated with Laramide shortening is observed from 70 to 45 Ma in the Cooks Range and 80 to 50 Ma in the Franklin Mountains, whereas the Carrizo Mountains were largely unaffected by this event; and (4) final cooling to near-surface temperatures began 30–25 Ma at all three locations and was likely a result of Rio Grande rift extension. These data help to bridge the gap between higher and lower temperature isotopic systems to constrain complex thermal histories in tectonically mature regions.

Oriented growth of sillimanite in andalusite, Placitas – Juan Tabo area, New Mexico, U.S.A.

1987 ◽  
Vol 24 (3) ◽  
pp. 580-590 ◽  
Author(s):  
R. H. Vernon
Keyword(s):  
New Mexico ◽  
Regional Metamorphism ◽  
Stacking Faults ◽  
Local Scale ◽  
Strain Accumulation ◽  
Oriented Growth ◽  
Screw Dislocations ◽  
Time Path ◽  
Granite Emplacement ◽  
Nucleation Sites

In metapelitic schists near the Sandia granite in the Placitas – Juan Tabo area, New Mexico, nucleation sites for sillimanite are very variable, but growth of sillimanite in andalusite is common, either as bundles of fibrous ("fibrolitic") sillimanite crystals or as coarser grained parallel prisms or dendritic crystals of sillimanite. Optical relationships indicate a coaxial relationship between the andalusite and the sillimanite but with a and b axes interchanged. Stacking faults formed by dissociated screw dislocations in the andalusite may have provided nucleation sites for sillimanite. Some large sillimanite grains appear to have formed by coarsening of fibrous sillimanite, but others show no evidence of such coarsening. Some fibrous sillimanite occurs in folia in zones of inferred noncoaxial strain accumulation. Some occurs in radiating or crystallographically controlled aggregates in low-strain zones between sillimanite folia. These aggregates do not necessarily indicate postdeformation growth, except on a very local scale, and many of the fibrous sillimanite aggregates have been deformed. Hence, the sillimanite is a product of syndeformational rather than post-deformational metamorphism, as previously suggested, although regional metamorphism and granite emplacement may have been broadly synchronous. The andalusite–sillimanite microstructural relationships indicate a prograde P–T–time path similar to those occurring in other low-pressure (andalusite–sillimanite) metamorphic areas.

Evolution of silicic magma in the upper crust: the mid-Tertiary Latir volcanic field and its cogenetic granitic batholith, northern New Mexico, U.S.A.

1988 ◽  
Vol 79 (2-3) ◽  
pp. 265-288 ◽  
Author(s):  
Peter W. Lipman
Keyword(s):  
New Mexico ◽  
Thermal Evolution ◽  
Volcanic Rocks ◽  
Volcanic Field ◽  
Granitic Rocks ◽  
Flow Sheet ◽  
Magmatic System ◽  
Calc Alkaline ◽  
Porphyritic Granite ◽  
Plutonic Rocks

ABSTRACTStructural and topographic relief along the eastern margin of the Rio Grande rift, northern New Mexico, provides a remarkable cross-section through the 26-Ma Questa caldera and cogenetic volcanic and plutonic rocks of the Latir field. Exposed levels increase in depth from mid-Tertiary depositional surfaces in northern parts of the igneous complex to plutonic rocks originally at 3–5 km depths in the S. Erosional remnants of an ash-flow sheet of weakly peralkaline rhyolite (Amalia Tuff) and andesitic to dacitic precursor lavas, disrupted by rift-related faults, are preserved as far as 45 km beyond their sources at the Questa caldera. Broadly comagmatic 26 Ma batholithic granitic rocks, exposed over an area of 20 by 35 km, range from mesozonal granodiorite to epizonal porphyritic granite and aplite; shallower and more silicic phases are mostly within the caldera. Compositionally and texturally distinct granites define resurgent intrusions within the caldera and discontinuous ring dikes along its margins; a batholithic mass of granodiorite extends 20 km S of the caldera and locally grades vertically to granite below its flat-lying roof. A negative Bouguer gravity anomaly (15–20 mgal), which encloses exposed granitic rocks and coincides with boundaries of the Questa caldera, defines boundaries of the shallow batholith, emplaced low in the volcanic sequence and in underlying Precambrian rocks. Palaeomagnetic pole positions indicate that successively crystallised granitic plutons cooled through Curie temperatures during the time of caldera formation, initial regional extension, and rotational tilting of the volcanic rocks. Isotopic ages for most intrusions are indistinguishable from the volcanic rocks. These relations indicate that the batholithic complex broadly represents the source magma for the volcanic rocks, into which the Questa caldera collapsed, and that the magma was largely liquid during regional tectonic disruption.Volcanic and plutonic magmas (1) changed from early high-K calc-alkaline to alkalic prior to caldera eruptions; (2) differentiated to a weakly peralkaline rhyolite and equivalent acmiteartvedsonite granite cap (underlain by calc-alkaline granite) when the caldera formed at 26·5 Ma; then (3) reverted to calc-alkaline compositions. Concentrations of alkalis and minor elements such as Rb, Th, U, Nb, Zr, and Y reached maxima at the caldera stage. The volcanic rocks constitute intermittently quenched samples of upper parts of Questa magma bodies at early stages of crystallisation; in contrast, the comagmatic granitic rocks preserve an integrated record of protracted crystallisation of the magmatic residue as eruptions diminished. Multiple differentiation processes were active during evolution of the Questa magmatic system: crystal fractionation, replenishment by mantle and lower crustal melts of varying chemical and isotopic character, mixing of evolved with more primitive magmas, upper crustal assimilation, and perhaps volatile-transfer processes. As a result, an evolving batholithic cluster of coalesced magma chambers generated diverse assemblages of broadly cogenetic rocks within a few million years. Evolution of the Questa magmatic system and similar high-level Tertiary granitic batholiths nearby in the southern Rocky Mountains provides broad insights into magmatic processes in continental regions such as the overall shapes of batholiths, time and compositional relations between cogenetic volcanic and plutonic rocks, density equilibration of magmas with country rocks, and thermal evolution of continental crust.

Guns, Alcohol, and Intimate Partner Violence: The Epidemiology of Female Suicide in New Mexico

Crisis ◽  
1999 ◽  
Vol 20 (3) ◽  
pp. 121-126 ◽  
Author(s):  
Lenora Olson ◽  
Frank Huyler ◽  
Arthur W Lynch ◽  
Lynne Fullerton ◽  
Deborah Werenko ◽  
...  
Keyword(s):  
Intimate Partner Violence ◽  
New Mexico ◽  
American Indians ◽  
Partner Violence ◽  
The United States ◽  
Intimate Partner ◽  
Injury Death ◽  
Female Suicide ◽  
Blood Alcohol Levels ◽  
Associated Risk Factors

Suicide is among the leading causes of death in the United States, and in women the second leading cause of injury death overall. Previous studies have suggested links between intimate partner violence and suicide in women. We examined female suicide deaths to identify and describe associated risk factors. We reviewed all reports from the New Mexico Office of the Medical Investigator for female suicide deaths occurring in New Mexico from 1990 to 1994. Information abstracted included demographics, mechanism of death, presence of alcohol/drugs, clinical depression, intimate partner violence, health problems, and other variables. Annual rates were calculated based on the 1990 census. The New Mexico female suicide death rate was 8.2/100,000 persons per year (n = 313), nearly twice the U. S. rate of 4.5/100,000. Non-Hispanic whites were overrepresented compared to Hispanics and American Indians. Decedents ranged in age from 14 to 93 years (median = 43 years). Firearms accounted for 45.7% of the suicide deaths, followed by ingested poisons (29.1%), hanging (10.5%), other (7.7%), and inhaled poisons (7.0%). Intimate partner violence was documented in 5.1% of female suicide deaths; in an additional 22.1% of cases, a male intimate partner fought with or separated from the decedent immediately preceding the suicide. Nearly two-thirds (65.5%) of the decedents had alcohol or drugs present in their blood at autopsy. Among decedents who had alcohol present (34.5%), blood alcohol levels were far higher among American Indians compared to Hispanics and non-Hispanic Whites (p = .01). Interpersonal conflict was documented in over 25% of cases, indicating that studies of the mortality of intimate partner violence should include victims of both suicide and homicide deaths to fully characterize the mortality patterns of intimate partner violence.

Child and Adolescent Suicide Deaths in New Mexico, 1990-1994

Crisis ◽  
2000 ◽  
Vol 21 (1) ◽  
pp. 36-44 ◽  
Author(s):  
DD Werenko ◽  
LM Olson ◽  
L Fullerton-Gleason ◽  
AW Lynch ◽  
RE Zumwalt ◽  
...  
Keyword(s):  
New Mexico ◽  
Cause Of Death ◽  
American Indians ◽  
Adolescent Suicide ◽  
Suicide Attempts ◽  
Medical Examiner ◽  
Contributing Factors ◽  
Targeted Interventions ◽  
And Gender ◽  
Youth Activity

The suicide death rate in New Mexico is consistently higher than the national rate. Among adolescents, suicide is the third leading cause of death nationally, but in New Mexico it is the second leading cause of death. This study describes the pattern of adolescent suicide deaths in New Mexico. We conducted a retrospective review of all medical examiner autopsies for adolescent suicides (ages 20 years and younger) in New Mexico from 1990-1994. Records were reviewed for demographics and possible contributing factors such as depression, previous attempts, and alcohol and drug use. We identified 184 suicide deaths among children and adolescents ages 9-20 years for an overall rate of 12.9 per 100,000. Our rates for ages 5-9 years (0.2), 10-14 years (3.8), and 15-19 years (22.3) are over twice the U.S. rates. Suicide deaths resulted primarily from firearms (67%), hanging (16%), poisoning (6%), inhalation (4%), and other methods (7%). Method varied by ethnicity (p = .01) and gender (p = .03); males and non-Hispanic Whites were overrepresented among firearm deaths. Firearm ownership was known in 60 (48%) of the firearm deaths. Of these, 53% of the firearms belonged to a family member, 25% to the decedent, and 22% to a friend. Over one-third of decedents (41%) experienced mental disorders, primarily depressed mood and clinical depression. Previous suicide attempts were noted for 15% of the decedents. Some 50% of the decedents had alcohol or drugs present at the time of death; among American Indians/Alaska Natives, 74% had drugs or alcohol present (p = .003). Targeted interventions are needed to reduce adolescent suicide in New Mexico. We suggest raising awareness about acute and chronic contributing factors to suicide; training physicians to look for behavioral manifestations of depression; and involving physicians, teachers, and youth activity leaders in efforts to limit firearm accessibility, such as advising parents to remove firearms from their households.

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