Renewed Heating Research Articles

Development of a Prototype Plant for the Heat Treatment of Workpieces with Preferably Bainitic Properties

Abstract In vehicle construction, components with high tensile strengths are used, especially in the chassis area. At the same time, these components must have high toughness and be insensitive to cracking. For this purpose, hardened and tempered but also salt-bainitized components are used. The associated usual process chain after steel production consists of forming processes with subsequent cooling of the forging blanks and subsequent heat treatment with renewed heating to set the required material properties. From an energy point of view, heat treatment from the forging heat is desirable, which in addition to shortening the process chain is also associated with a reduction in CO2 emissions. A prototype system for controlled bainitization has been developed, which implements the heat treatment immediately after hot forming by utilizing the still existing forming temperature. Here, a controlled spray field generates both a quenching and an isothermal holding phase. Various sensors generate input variables to cool the workpieces in a controlled manner. This paper gives an overview of the system technology, realized cooling curves and the resulting hardness.

Polymetamorphism in high‐T metamorphic rocks: An example from the central Appalachians

AbstractContact metamorphism associated with mafic intrusives is one of several mechanisms that has been invoked to produce extensive high‐temperature (HT) metamorphism and associated partial melting of the crust. Indisputable evidence for polymetamorphism in these settings can be difficult to decipher because both melt loss and retrogression (i.e. rehydration) can erase or obscure the records of earlier HT metamorphism by modifying HT mineral parageneses and compositions. Here, a combination of detailed field and petrographical observations, inverse mineral thermometry, and thermodynamic forward modelling is used to delineate the polymetamorphic history of migmatites from the Smith River Allochthon (SRA) in the central Appalachians. Bulk rock geochemical data suggest that some metapelitic samples lost a significant amount of melt during interpreted contact metamorphism with the Rich Acres gabbro, resulting in a residual bulk composition (<50 wt% SiO2, ~30 wt% Al2O3). Garnet cores (Grt1) in SiO2‐depleted samples are interpreted to grow during this HT contact metamorphism, with Fe‐Ti oxide thermometry on spinel inclusions in Grt1, cordierite–garnet thermometry, and thermodynamic forward modelling constraining peak P–T conditions during contact heating of the migmatites to ~800ºC and ∼0.5 GPa. This is associated with an inferred peak assemblage prior to melt loss of crd+kfs+pl+grt+bt+spl (mag+usp+hc)+ilm+sil+qtz+melt. Garnet in SiO2‐depleted samples has a distinct high‐Ca rim (Grt2), which appears to record a younger metamorphic event. A combination of substantial melt loss and later rehydration appears to be a major control on the ability of SiO2‐depleted samples to faithfully record evidence for this polymetamorphism. The tectonic implications of this younger metamorphic event are not entirely clear, but it appears to record renewed burial and heating of the SRA sometime after the Taconic orogeny, which may be related to either the neo‐Acadian or Alleghanian orogenies.

도서관의 공간사용 특성에 따른 냉난방설비 리모델링의 경제성 평가

ABSTRACT:Unlike the previous approaches, we analyzed for economic efficiency of renewed heating and cooling systems as the characteristics of space. The purpose of this study is to analysis the energy consumption and economical efficiency of absorption chillers and EHP systems in renovated library. It is important that equipment selection should be considering energy cost as well as space program. In recently, many EHP systems were installed in the building for reducing the energy cost and for seeking the convenience of individual control. In contrast, though absorption chillers have the disadvantage of a central control, absorption chillers are appropriate for the conditions of the library that needs simultaneous operation. The results by payback period method, show that selection of heating and cooling systems should be consider for space program and the characteristics of space. Keywords:Building energy(건물 에너지), Library remodeling(도서관 리모델링), Electric heat pump (EHP), Absorption chiller(흡수식 냉온수기), Payback period(투자비 회수 기간)

Intracontinental orogenesis in an ancient continent–continent collision zone: Evidence from structure, metamorphism and P-T paths across a suspected suture zone within the Eastern Ghats Belt, India

In the Eastern Ghats Belt of India, deformation and granulite facies metamorphism are generally correlated with India–Antarctica collision during the assembly of Rodinia. Within the belt, Archean granulites in the west are separated from Proterozoic granulites to the east by a prominent lithotectonic contact. Recent studies assume this contact to be the suture zone related to collision, although the structural and metamorphic evolution of the Archean granulites are so far undescribed. In this study, an integrated structural and metamorphic study conducted across the contact reveals that each unit preserves unrelated early granulite facies fabrics, but subsequently shared a top-to-the-west thrusting event that imprinted a penetrative NE–SW trending, southeasterly dipping shear foliation along the boundary zone. Syn-thrusting fluid infiltration initially stabilized hydrous minerals at the cost of earlier granulite facies assemblages in both units. Renewed heating and loading then re-established granulite facies conditions in both units, with peak conditions around 8kb, 750–800°C, possibly in the mid-Neoproterozoic time. Since metamorphic conditions and P-T trajectories are similar across the contact, the pre-thrusting thermal structure in both units is inferred to be similar. This implies that both units were already amalgamated into a common footwall block prior to this shared tectonothermal event. No ophiolites, arc magmas or post-collisional granitic activity of Neoproterozoic age are associated with this contact. It is concluded that the contact between Archean and Proterozoic granulites in the Eastern Ghats Belt is not a suture but records intracontinental orogenesis within the collision belt that either predates or post-dates the Proterozoic India–Antarctica amalgamation.

Composition and thermal evolution of the lithospheric mantle beneath the Harrat Uwayrid, eastern flank of the Red Sea rift (Saudi Arabia)

Harrat Uwayrid is one of several volcanic fields that developed along the western margin of the Arabian plate during opening of the Red Sea rift. Volcanic activity started in the late Miocene and Pliocene with the eruption of alkaline flood basalts. After a period of extensional faulting, numerous cinder cones formed in the central part of the volcanic field during the Quaternary. Xenoliths of both mantle and crustal origin are abundant. The mantle-derived suite is dominated by spinel lherzolite with X Mg of olivine and X Cr of spinel ranging from 0.868 to 0.911 and from 0.074 to 0.636, respectively. In addition to lherzolite, various types of pyroxenites and wehrlites occur. Most xenoliths contain primary and/or secondary amphibole (pargasite/kaersutite), indicating at least two enrichment events, both related to the formation of the Red Sea. Chemical zonation profiles of mineral grains constrain the thermal evolution of the xenoliths and their source regions in the shallow upper mantle. Ca contents in olivine are constant in the inner parts of the grains, but increase in the outermost zones (< 35 μm). X Mg values of spinel grains adjacent to olivine often show a rimward increase in their outer zones (< 150 μm). Both types of zonation patterns are interpreted to result from heating by the host magma during transport. Zonation patterns of Al and Ca/(1 − Na) in pyroxene grains record different thermal evolutions, such as (i) simple cooling, whereby a ‘near-equilibrium’ state was rarely achieved, (ii) cooling followed by heating, and (iii) simple heating. Diffusion modelling on measured zoning profiles suggests that cooling lasted for no more than ∼ 10 Myr. Temperature estimates for pyroxene core and rim compositions, calculated by using various pyroxene geothermometers range from ∼ 800 to 1140 °C (at an assumed pressure of 1.5 GPa). In conjunction with upper pressure limits derived from the composition of spinel, these values imply relatively high temperatures for the shallow upper mantle. This is corroborated by P– T estimates for spinel lherzolites obtained by combination of the two-pyroxene thermometer based on the solvus between enstatite and diopside and the Ca-in-olivine geothermobarometer. While the high- T state that preceded cooling was probably a regional phenomenon, renewed heating was of local nature, most probably related to advective heat transport by ascending and stagnating magmas.

Stockholm CHP potential—An opportunity for CO 2 reductions?

The potential for combined heat and power (CHP) generation in Stockholm is large and a total heat demand of about 10 TWh/year can be met in a renewed large district heating system. This model of the Stockholm district heating system shows that CHP generation can increase from 8% in 2004 to 15.5% of the total electricity generation in Sweden. Increased electricity costs in recent years have awakened an interest to invest in new electricity generation. Since renewable alternatives are favoured by green certificates, bio-fuelled CHP is most profitable at low electricity prices. Since heat demand in the district heating network sets the limit for possible electricity generation, a CHP alternative with a high electricity to heat ratio will be more profitable at when electricity prices are high. The efficient energy use in CHP has the potential to contribute to reductions in carbon dioxide emissions in Europe, when they are required and the European electricity market is working perfectly. The potential in Stockholm exceeds Sweden's undertakings under the Kyoto protocol and national reduction goals.

Numerical simulation of petroleum generation and migration in the Qingshui sag, western depression of the Liaohe basin, northeast China

A two-dimensional basin-modeling study was employed to analyze the petroleum generation and migration history of the Qingshui sag in the western depression of the Liaohe basin, northeast China. The Eocene–Oligocene ES4 and ES3 members of the Shahejie Formation (ES) are the most important source rocks responsible for the major hydrocarbon accumulations. Two sandstone beds of fan-delta origin, the Dujiatai (DJT) and the Xinglongtai (XLT), are the primary reservoir rocks in the study area. The model indicates that two migration systems can be differentiated; they are separated by the thick shale beds of the middle ES3 and ES1, which acted as important regional seals for the lower and the upper systems, respectively. The DJT bed is the most important pathway for migrating hydrocarbons in the lower system, whereas the XLT bed is a significant factor in the upper system. Calibration of the model with thermal maturity data indicates that the geological evolution is consistent with typical heat-flow values for rift basins in the range between 85 and 48 mW/m2. All source units reached maturity during the major burial phase, which extended from the Oligocene to the Eocene. Simulation results further indicate that after a cooling period, renewed heating occurred, and additional hydrocarbons were generated during the last 5 m.y., particularly in the southern part of the basin. Sensitivity tests indicated that the faults, particularly the two main faults, served as important conduits for petroleum throughout most of the geological history. The main phase of migration occurred between the Eocene and Oligocene and was responsible for major accumulations in the west slope, the central anticline, and the central rise. Additional migration between 5 Ma and the present is significant in the southwestern area and may have brought about petroleum accumulation in the central depression and central rise.

Thermal and tectonic evolution of the Falkland Islands: implications for hydrocarbon exploration in the adjacent offshore region

Apatite fission track and vitrinite reflectance data combine to suggest that the Falkland Islands experienced three discrete episodes of heating and cooling during the Phanerozoic, each of which can be related to major changes in the plate tectonic setting of the islands. Combined with published data from the adjacent offshore areas, the results provide unique insights into the behaviour of the region during the phases of convergent and divergent tectonic movements that have affected the region since the Permian. Initial cooling of the Falkland Islands in the Late Permian was initially restricted to West Falkland, and was the result of differential uplift and erosion of West Falkland relative to East Falkland, coinciding with D2 Gondwanian deformation. Subsequent Early Jurassic cooling of both East and West Falkland was associated with plume-related thermal uplift preceding the separation of East and West Gondwana and the development of the Falkland Plateau Basin. The Falkland Islands experienced renewed heating during the Mesozoic, probably due to increased burial, suggesting that the offshore basins originally extended onto the present onshore region. Late Cretaceous/Early Tertiary cooling of the Falkland Islands was contemporaneous with the development of a transpressional plate boundary along the southern margin of the Falkland Plateau resulting in erosion of the islands that were situated on a flexural forebulge.

Multiple generations of extensional detachments in the Rhodope Mountains (northern Greece): evidence of episodic exhumation of high-pressure rocks

Abstract An integrated structural and petrological study shows that exhumation of high- P rocks of the Rhodope occurred in several pulses. The structurally uppermost Kimi Complex recording an Early Cretaceous high- P metamorphism was exhumed between about 65 and &gt;42 Ma. The Sidironero, Kardamos and Kechros Complexes that record Early Tertiary high- P metamorphism (at least 19 kbar at 700 °C) were exhumed at &gt;42–30 Ma. Exhumation occurred with isothermal decompression. Strain episodes depict thrusting of medium/high grade above lower grade high- P rocks, syn-thrusting extension and post-thrusting extension. Polyphase extension created several generations of detachment zones, which, in sum, excise about 20 km of material within the crustal profile. This reduction in crustal thickness is consistent with a reduction of the present crustal thickness from more than 40 km to less than 30 km in the eastern Rhodope. We mapped the post-thrusting Xanthi low-angle detachment system over 100 km, from its break up zone above the Sidironero Complex (Central Rhodope) into the eastern Rhodope. This detachment shows an overall ESE-dip with a ramp and flat geometry cutting across the earlier thrust structures. The Kimi Complex is the hanging wall of all syn- and post-thrusting extensional systems. On top of the Kimi Complex, marine basins were formed from the Lutetian ( c. 48–43 Ma) through the Oligocene, during extension. Successively, at c. 26 to 8 Ma, the Thasos/Pangeon metamorphic core complexes were exhumed. In these times representing the early stages of Aegean back-arc extension, the Strymon and Thasos detachment systems caused crustal thinning in the western Rhodope. Renewed heating of the lithosphere associated with magmatism and exhumation of hot middle crust from beneath the Sidironero Complex occurred. We focus on the geometry, timing and kinematics of extension and contraction structures related to the &gt;42–30 Ma interval and how these exhumed high- P rocks. We interpret high- P rocks exhumed in this interval as a window of the Apulian plate beneath the earlier (in the Cretaceous) accreted Kimi Complex.

Metamorphic Evolution of Garnet-Epidote-Biotite Gneiss from the Moine Supergroup, Scotland, and Geotectonic Implications

Metapelitic gneisses from the Glenfinnan Group of the Moine Supergroup, Scotland, contain sparse large and numerous small garnets, associated with complex zoned epidote and plagioclase in a biotite matrix. The large garnets show four zones (AI–AIV), whereas the small garnets show three or fewer zones, indicating successive garnet nucleation with increasing nucleation densities. Garnet zones AI and AIV grew under static conditions, whereas the formation of AII and AIII was accompanied by deformation. Garnet zones AI and AII were formed in the assemblage (all + biotite + epidote + plagioclase + quartz + fluid + apatite) garnet + chlorite + muscovite ± ilmenite ± sphene ± magnetite; zone AIII in the assemblage garnet + muscovite + sphene ± magnetite; and zone AIV in the assemblage garnet + sphene ± ilmenite. The chemical zonation and microstructures of garnet A indicate two important discontinuities; one at the transition between garnet zones AI and AII, and a second between zones AII and AIII, which correlate with complex zonation shown by epidote and plagioclase. These discontinuities may result from polymetamorphic garnet growth during different orogenic cycles affecting the Moine Supergroup. Geothermobarometric calculations and Gibbs method modelling provide evidence that garnet zone AI grew rapidly during heating from about 550 to 560°C at pressures of about 4–6 kbar. In contrast, the formation of zone AII was accompanied by nearly isothermal compression from 6 to 8·5 kbar (560 575°C), indicating crustal stacking. After a certain period of cooling, garnet zone AIII grew during renewed heating at P–T conditions of about 640°C and pressures between 5 and 9 kbar. Growth of garnet AIV was accompanied by further temperature rise, reaching maximum conditions of about 670°C at 5 kbar.

Eastern Alpine tectono‐metamorphic evolution: Constraints from two‐dimensional P‐T‐t modeling

We use two‐dimensional (2‐D) P‐T‐t modeling to constrain the thermal and rheological aspects of different scenarios for the late Mesozoic and Cenozoic tectonic evolution of the Eastern Alps, inferred from excellent data sets from the Tauern Window (TW). Models invoking subduction of the South Penninic (SP) oceanic lithosphere during thrusting and subsequent erosion of the Austro‐Alpine (AA) upper plate nappe stack are inconsistent with the observed thermal evolution within the AA and Penninic units. In these models, predictions for the AA peak thermal conditions are lower than observed. After exhumation and cooling to midcrustal levels and subduction of the continental Middle Penninic (MP) block, the AA undergoes a phase of renewed heating to almost the previous peak temperatures. Simultaneously, the Penninic units experience a phase of heating upon subduction, followed by cooling after onset of subduction of the North Penninic (NP) basin. The model predictions are inconsistent with the observed nearly isothermal uplift path of the SP after subduction and cannot explain observed inverted metamorphic peak conditions in the deeper AA (amphibolite facies) down to the higher Penninic unit (greenschist facies). A model with the beginning of subduction of the SP occurring after crustal thickening of the AA and subsequent return to normal crustal thicknesses is compatible with the P‐T‐t data. In this model, peak temperature conditions are higher in the AA, followed by a phase of strong cooling in the AA upper plate with the onset of underthrusting. This model also explains successfully nearly isothermal exhumation of the MP and inverted metamorphic peak conditions in the deeper AA. Material accreted to the hanging wall from the oceanic crust (SP) experiences a phase of cooling during ongoing subduction of oceanic lithosphere and begins to heat up to its thermal climax after the subduction of trailing continental lithosphere. The subsequent PT path of the Penninic units strongly depends on the timing and rates of underthrusting by the foreland. Observed PT paths in the MP within the TW require continuous subduction of the NP and the trailing European foreland under the exhuming MP block. Documented rapid cooling in the final uplift phase of the Penninic units in the TW requires exhumation rates up to approximately 4 mm/yr. Predictions of slightly elevated present‐day geothermal gradients in the TW area are consistent with available heat flow data. As a result of Mesozoic rifting followed by late Mesozoic crustal thickening of the AA, paleorheological reconstructions are characterized by a contrast between relatively strong oceanic lithosphere and adjacent weak continental lithosphere. Predicted decoupling of weak continental and oceanic lithosphere during subsequent subduction of the Penninic units can explain observed Late Cretaceous crustal extension in the AA units in terms of gravitational spreading. Ongoing subduction leads to an overall strength increase due to underthrusting of cool oceanic lithosphere, whereas subduction of continental lithosphere causes a strength decrease in the upper levels of the lithosphere. Continuous crustal thickening and relaxation of the depressed isotherms reduce the strength of the lower lithospheric mantle beneath the central orogen, further enhanced by rapid late‐stage uplift. Predictions for the present‐day rheological structure of the Eastern Alps support the existence of a strong upper crustal layer, two wedge‐shaped strong upper mantle layers to the north and the south of the orogen, and a weak upper mantle underlying the central orogen.

Polymetamorphism and isobaric cooling of pelitic schists from the Annex sulphide deposit, Gordonia Belt, South Africa

Abstract Muscovite‐poor pelitic schists in the wallrocks of the Proterozoic Annex sulphide deposit, near Prieska, South Africa, contain peak metamorphic assemblages including Crd + Bt + Sil, St + Sil + Bt, Crd + St + Bt and, rarely, Ky + St ° Crd. All rocks include oligoclase, quartz and commonly Fe–Mn garnet, with or without muscovite. Peak assemblages, assigned to M2 regional metamorphism in the Gordonia Belt (Namaqua Province), are syn‐ to post‐kinematic with respect to the main S2 fabric although larger staurolite grains contain S1 inclusion trails. Garnet–biotite thermometry, utilizing corrections for Fe3+, Mn, AlVI and Ti, yields peak temperatures of 571–624°C at pressures of 4.5–6.0 kbar. Consideration of the sympathetic variation of XMn in garnet with XMg in biotite and the preserved zoning patterns in prograde garnets, together with the inferred prograde transition from kyanite to sillimanite, indicates that heating occurred during mild decompression to the M2 metamorphic peak. Sillimanite and cordierite grew last in the prograde sequence, possibly related to a pulse of thermal metamorphism (M3) that is found along the margin of the Keimoes Suite batholith to the north.Retrograde assemblages, including Ms + Ky + Chl + Qtz (after Crd + Bt), Ky + Ms (after Sil) and Chl + Ms (after St) indicate a period of isobaric cooling (M4a) terminated by rehydration in the kyanite stability field at about 500°C.The size difference between prograde (1–2‐mm) and retrograde (0.05–0.1‐mm) mineral grains indicates substantial undercooling below equilibrium positions of relevant retrograde reactions prior to rehydration, and explains why cordierite that grew during M2 is almost completely destroyed. Post‐M4a regrowth of staurolite and garnet (M4b) is spatially linked to sites of M4a rehydration. It reached temperatures of 510–530°C, remaining within the stability field of kyanite.A best fit of the observed textural history to the Namaqua orogenic cycle involves collision and heating (M2/D2) followed by granite intrusion (M3), rifting (M4a) and renewed heating due to crustal loading during volcanism (M4b). The P–T path for the Annex region is consistent with those derived from elsewhere in the Gordonia Belt and, with modification, to that published already for the nearby Prieska Copper Mines.

Renewed Petroleum Generation Related to Tertiary Intrusions and Increased Heat Flow, Western Permian Basin, Texas and New Mexico: ABSTRACT

Higher paleogeothermal gradients, commencing in the Tertiary after maximum burial, have caused renewed petroleum generation in the western Permian basin. Evidence for this reheating is two distinct trends in the mean random vitrinite reflectance (R/sub m/) and depth data compiled from over 40 wells. One group, with a 0.7% R/sub m//km gradient, is from the western edge of the basin; the other, with a 0.5% R/sub m//km gradient, is from the central and eastern portions. Post-Mississippian tilting produced greater subsidence and a thicker, mostly uneroded sedimentary section in the eastern portion of the Permian basin. Continued tilting prior to the Cretaceous caused uplift and erosion that exposed the Upper Permian section in the western part. Potassium-argon ages of igneous intrusions along the western edge of the basin show they were emplaced about 35 Ma, followed by Miocene to Holocene basin-and-range-type block faulting and associated high heat flow. Isopach-reflectance contours confirm this renewed heating is post-tectonic - that is, it occurred after eastward tilting and erosion had reduced burial depth. Maximum temperatures computed from R/sub m/-depth relationships infer that paleogeothermal gradients exceeded 40/degrees/C/km (2.2/degrees/F/100 ft) in the Tertiary. This reheating thermally matured rocks as young as Guadalupian in the western Permianmore » basin and apparently caused a second episode of petroleum generation. By this time, however, the potential reservoir rocks and evaporite seals had been deeply eroded, resulting in poor conditions for trapping the renewed pulse of petroleum.« less

Vertical movement in orogenic belts and the timing of metamorphism relative to deformation

Summary Any phase of deformation in an orogenic belt that causes relative vertical movements of bodies of rock by a few kilometres or more should have a recognizable imprint in the metamorphic history. The effect seen in a P-T-t path will depend on whether the rock body examined moved relatively up or down in the orogenic pile. An upthrown block is predicted to cool soon after the onset of movement, but the resulting P-T path will be insignificantly different to that resulting from a cycle of thickening and erosion. A downthrown block will undergo renewed heating after movement, and evidence of the earlier metamorphic history will probably be overprinted. It is suggested that the recognition of phases of relative vertical movement in an orogenic belt is best made by combined studies of deformation-metamorphism textural relationships, and P-T-t paths. The Lukmanier Pass area of the Alps illustrates the textural patterns predicted: here, a phase of deformation immediately post-dates the metamorphic peak, suggesting uplift of the area relative to the Helvetic nappes to the north.

Hydrothermal brecciation in the Jemez fault zone, Valles Caldera, New Mexico: Results from continental Scientific Drilling Program core hole VC‐1

An unusual breccia sequence penetrated in the lower 30 m of Continental Scientific Drilling Program core hole VC‐1 (total depth 856 m) records a complex hydrothermal history culminating in hydraulic rock rupture and associated alteration at the edge of the Quaternary Valles caldera. The breccias, both tectonic and hydrothermal in origin, were formed in the Jemez fault zone, near the intersection of this major regional structure with the caldera's ring‐fracture margin. Tectonic breccias in the sequence are contorted, crushed, and sheared. Coexisting hydrothermal breccias lack such frictional textures but display matrix flow foliation and prominent clast rounding, features characteristic of fluidization. These hydrothermal breccias were intensely altered, during at least five major stages, to quartz‐illite‐phengite‐pyrite aggregates; traces of molybdenite occur locally. This assemblage indicates interaction with hydrothermal fluid at temperatures in excess of 200°C. The extrapolated present maximum temperature of 184°C in the breccia zone therefore represents considerable cooling since these phases were formed. Fluid inclusions in the breccias also preserve evidence of the prior passage of hotter fluids. The inclusions are principally two phase, liquid rich, secondary in origin, and concentrated in hydrothermal quartz. Older, high‐salinity inclusions, unrelated to brecciation, homogenize in the temperature range 189°–246°C. Younger inclusions, in part of interbreccia origin, are low‐salinity and homogenize in the temperature range 230°–283°C; locally coexisting liquid‐ and vapor‐rich inclusions document periodic boiling of the dilute fluids. These fluid‐inclusion data, along with the probable age of the hydrothermal breccias (&lt;1.5 Ma), the assumed depth at which they developed (about 515 m), and the contemporaneous state of stress (extensional) can be combined to model hydrothermal brecciation at the VC‐1 site. The minimum fluid pressure (Pfr) required to hydrofracture these rocks was probably about 7.5 MPa (0.0146 MPa/m). A boiling point versus depth curve based on these Pfr values graphically defines the physical conditions prevailing when the breccias were formed. When fluid pressure at the assumed depth of brecciation exceeded that curve, in response to rapid release of confining pressure possibly augmented by renewed heating, flashing hydrothermal fluid fractured the enclosing rock. Large overpressures, most likely induced by sudden seismic cracking of a hydrothermally sealed portion of the Jemez fault zone, led to local fluidization of the resulting breccias. Late quartz veining, hydrothermal alteration, and molybdenite mineralization were probably produced by the fluids responsible for brecciation.

Effect of partial cooling and repeated heating in hardening on the structure and properties of nitrided parts made of steel 25KhGM

To reduce warping of parts it is recommended [i] to cool them partially to not below 800°C before quenching. If parts are to be straightened, it is indispensable to ensure that their core is soft; this is possible if they are partially cooled to below the temperature Ar~ However, it may happen that~this is accompanied by loss of hardness of the nitrided case, which can be corrected by renewed heating to 30-50°C above Acl [2]. In connection with this it was of practical interest to investigate the effect of partial cooling and renewed heating before quenching on the structure, the hardness, and the warping of nitrided parts made of steel 25KhGM.

Anatomy, Age and Evolution of the Baltoro granite batholith, Pakistani Karakoram

DOI = 10.3126/hjs.v5i7.1319 Himalayan Journal of Sciences Vol.5(7) (Special Issue) 2008 p.137