scholarly journals METAMORPHIC EVOLUTION OF GARNET–BIOTITE–MUSCOVITE SCHIST FROM BARRU COMPLEX IN SOUTH SULAWESI, INDONESIA

2015 ◽  
Vol 6 (2) ◽  
Author(s):  
Nugroho Imam Setiawan ◽  
Yasuhito Osanai ◽  
Nobuhiko Nakano ◽  
Tatsuro Adachi
Keyword(s):  
Geothermal Gradient ◽  
Metamorphic Rocks ◽  
Metamorphic Evolution ◽  
First Report ◽  
Geothermal Gradients ◽  
South Sulawesi ◽  
Pelitic Schist ◽  
T Path ◽  
Tectonic Environments

This paper explains the first report in metamorphic evolution of pelitic schist from Barru Complex in South Sulawesi, Indonesia. Garnet-biotitemuscovite schist was examined petrologically to assess the metamorphic evolution history, which has implications on tectonic condition of this region. The rock mainly composed of garnet, biotite, muscovite, epidote, quartz, rutile, hematite, and plagioclase. Inclusions in the garnet preserve records of prograde stage of this rock, which are epidote, titanite, quartz, and apatite. Garnet, biotite, muscovite, quartz, rutile, and plagioclase are concluded as equilibrium assemblages at peak P-T condition of this rock, which estimated at 501–562 ºC and 0.89–0.97 GPa. The result is still on the ranges of the estimated geothermal gradient P-T path of eclogite from Bantimala Complex. Similar geothermal gradients of metamorphisms might be indicated that these metamorphic rocks were metamorphosed on the similar tectonic environments. Keywords: Pelitic schist, Barru Complex, South Sulawesi, metamorphic evolution.

scholarly journals STUDY OF THE METAMORPHIC EVOLUTION OF A CARBONATE-BEARING METAPERIDOTITE FROM THE SIDIRONERO COMPLEX (CENTRAL RHODOPE, GREECE) USING P-T AND P(T)-XCO2 PSEUDOSECTIONS

2017 ◽  
Vol 43 (5) ◽  
pp. 2667
Author(s):  
E. Mposkos ◽  
I. Baziotis
Keyword(s):  
Phase Diagram ◽  
Fluid Phase ◽  
Bulk Rock ◽  
Prograde Metamorphism ◽  
Metamorphic Evolution ◽  
Rock Composition ◽  
Bulk Rock Composition ◽  
Hp Metamorphism ◽  
T Path

The carbonate-bearing metaperidotite from Sidironero Complex, north of the Xanthi town is composed primarily of olivine and orthopyroxene megacrysts and of Ti-clinohumite, tremolite, chlorite, dolomite, magnesite, talc, antigorite and spinel group minerals. The metaperidotite underwent a prograde HP metamorphism probably isofacial with the neighboring amphibolitized eclogites. Calculated P-T and P(T)-XCO2 phase diagram sections (pseudosections) for the bulk rock composition showed that XCO2 in the fluid phase was extremely low (≤0.008) at the first stages of the metamorphism and increased up to 0.022 at the peak P-T conditions ~1.5 GPa and 690 0C. The prograde metamorphism probably started from a hydrated and carbonated assemblage including talc+chlorite+magnesite+dolomite and proceeded with tremolite and antigorite formation before olivine growth, and orthopyroxene formation after olivine growth (Ol-1). Matrix dolomite, breakdown of chlorite (Chl-1) to Cr spinel+olivine and of Ti-clinohumite to olivine+Mg-ilmenite occurred during decompression. The P-T path is constrained by the absence of clinopyroxene in the metaperidotite.

scholarly journals Evaluation of geothermal energy resources in parts of southeastern sedimentary basin, Nigeria

2021 ◽  
Vol 23 (1) ◽  
pp. 195-211
Author(s):  
I.M. Okiyi ◽  
S.I. Ibeneme ◽  
E.Y. Obiora ◽  
S.O. Onyekuru ◽  
A.I. Selemo ◽  
...  
Keyword(s):  
Spectral Analysis ◽  
Heat Flow ◽  
Curie Point ◽  
Geothermal Energy ◽  
Sedimentary Basin ◽  
Geothermal Gradient ◽  
Geothermal System ◽  
Magnetic Vector ◽  
Geothermal Gradients ◽  
Vector Inversion

Residual aeromagnetic data of parts of Southeastern Nigerian sedimentary basin were reduced to the equator and subjected to magnetic vector inversion and spectral analysis. Average depths of source ensembles from spectral analysis were used to compute depth to magnetic tops (Z), base of the magnetic layer (Curie Point t Depth (CPD)), and estimate geothermal gradient and heat flow required for the evaluation of the geothermal resources of the study area. Results from spectral analysis showed depths to the top of the magnetic source ranging between 0.45 km and 1.90 km; centroid depths of 4 km - 7.87 km and CPD of between 6.15 km and 14.19 km. The CPD were used to estimate geothermal gradients which ranged from 20.3°C/km to 50.0°C/km 2 2 and corresponding heat flow values of 34.9 mW/m to 105 mW/m , utilizing an average thermal conductivity -1 -1 of 2.15 Wm k . Ezzagu (Ogboji), Amanator-Isu, Azuinyaba, Nkalagu, Amagunze, Nta-Nselle, Nnam, Akorfornor environs are situated within regions of high geothermal gradients (>38°C/Km) with models delineated beneath these regions using 3D Magnetic Vector Inversion, having dominant NW-SE and NE-SW trends at shallow and greater depths of <1km to >7 km bsl. Based on VES and 2D imaging models the geothermal system in Alok can be classified as Hot Dry Rock (HDR) type, which may likely have emanated from fracture systems. There is prospect for the development of geothermal energy in the study area. Keywords: Airborne Magnetics, Magnetic Vector Inversion, Geothermal Gradient, Heat Flow, Curie Point Depth, Geothermal Energy.

scholarly journals An anticlockwise metamorphic P-T path and nappe stacking in the Reisa Nappe Complex in the Scandinavian Caledonides, northern Norway: evidence for weakening of lower continental crust before and during continental collision

2018 ◽  
Author(s):  
Carly Faber ◽  
Holger Stünitz ◽  
Deta Gasser ◽  
Petr Jeřábek ◽  
Katrin Kraus ◽  
...  
Keyword(s):  
Partial Melting ◽  
Continental Crust ◽  
Large Scale ◽  
Structural Data ◽  
Geothermal Gradient ◽  
Continental Collision ◽  
Crustal Thickening ◽  
Northern Norway ◽  
Nappe Complex ◽  
T Path

Abstract. This study investigates the Caledonian metamorphic and tectonic evolution in northern Norway, examining the structure and tectonostratigraphy of the Reisa Nappe Complex (RNC; from bottom to top, Vaddas, Kåfjord and Nordmannvik nappes). Structural data, phase equilibrium modelling, and U-Pb zircon and titanite geochronology are used to constrain the timing and P-T conditions of deformation and metamorphism that formed the nappes and facilitated crustal thickening during continental collision. Five samples taken from different parts of the RNC reveal an anticlockwise P-T path attributed to the effects of early Silurian heating followed by thrusting. An early Caledonian S1 foliation in the Nordmannvik Nappe records kyanite-grade partial melting at ~ 760–790 °C and ~ 9.4–11 kbar. Leucosomes formed at 439 ± 2 Ma (U-Pb zircon) in fold axial planes in the Nordmannvik Nappe indicate that compressional deformation initiated while the rocks were still partially molten. This stage was followed by pervasive solid-state shearing as the rocks cooled and solidified, forming the S2 foliation at 680–730 °C and 9.5–10.9 kbar. Multistage titanite growth in the Nordmannvik Nappe records this extended metamorphism between 444 and 427 Ma. In the underlying Kåfjord Nappe, garnet cores record lower P-T (590–610 °C and 5.5–6.8 kbar) but a similar geothermal gradient as the S1 migmatitic event in the Nordmannvik Nappe, indicating formation at a higher relative position in the crust. S2 shearing in the Kåfjord Nappe occurred at 580–605 °C and 9.2–10.1 kbar, indicating a considerable pressure increase during nappe stacking. Gabbro intruded in the Vaddas Nappe at 439 ± 1 Ma, synchronously with migmatization in the Nordmannvik Nappe. In the Vaddas Nappe S2 shearing occurred at 630–640 ºC and 11.7–13 kbar. Titanite growth along the lower RNC boundary records S2-shearing at 432 ± 6 Ma. It emerges that early Silurian heating (~ 440 Ma), probably resulting from large-scale magma underplating, initiated partial melting that weakened the lower crust, which facilitated dismembering of the crust into individual nappe units. This tectonic style contrasts subduction of mechanically strong continental crust to great depths.

scholarly journals Intrusion of UHP metamorphic rocks into the upper crust of Kyrgyzian Tien-Shan: P-T path and metamorphic age of the Makbal Complex

2010 ◽  
Vol 105 (5) ◽  
pp. 233-250 ◽  
Author(s):  
Michio TAGIRI ◽  
Shingo TAKIGUCHI ◽  
Chika ISHIDA ◽  
Takaaki NOGUCHI ◽  
Makoto KIMURA ◽  
...  
Keyword(s):  
Tien Shan ◽  
Metamorphic Rocks ◽  
Upper Crust ◽  
T Path

The uplift of high-pressure-low-temperature metamorphic rocks

1987 ◽  
Vol 321 (1557) ◽  
pp. 87-103 ◽  
Keyword(s):  
Tectonic Setting ◽  
Geothermal Gradient ◽  
Dominant Mode ◽  
Metamorphic Rocks ◽  
Return Flow ◽  
Accretionary Wedge ◽  
Moderate Amount ◽  
Low Viscosity ◽  
Buoyancy Forces ◽  
Flowing Material

The uplift of high- P -low- T metamorphic rocks has been attributed to buoyancy, diapirism, or hydrodynamically driven return flow. Buoyancy forces can return material subducted into the mantle only if subduction slows or ceases, reducing the downward traction. The buoyancy forces will be reversed within the crust, because of the increased density of high- P assemblages, and therefore can not cause the subducted material to rise beyond the base of the crust. Diapirism and hydrodynamic flow processes require a low-density, low-viscosity matrix, and can only explain the emplacement of relatively small bodies of high- P rock entrained in the flowing material. The tectonic setting of coherent regional high- P —low- T terrains can be explained in terms of the mechanical behaviour of an accretionary wedge with negligible yield strength, where underplating is the dominant mode of accretion. Underplating thickens the wedge from beneath and increases its surface slope. This causes the upper part of the wedge to extend horizontally, even though convergence is continuing. Continued underplating beneath and extension above can allow the oldest high- P rocks to rise to within reach of a moderate amount of erosion on a time scale of the order of 10 Ma. As long as subduction continues beneath the wedge, the geothermal gradient will not relax to a normal value. This process explains (a) the evidence that high- P -low- T rocks are commonly uplifted while convergence is continuing; (b) the absence in many cases of significant overprinting by higher- T assemblages; (c) the position of the oldest and highest pressure rocks in the upper rear of orogenic wedges; (d) the lack of adequate tectonic thicknesses of overlying rock to explain the metamorphism; and (e) the common occurrence of post-metamorphic faults that excise parts of the metamorphic zonation.

Viscous relaxation of mineral Inclusions and its implications for reaction overstepping calculations in metamorphic rocks

2020 ◽  
Author(s):  
Evangelos Moulas ◽  
Xin Zhong ◽  
Lucie Tajcmanova
Keyword(s):  
Independent Method ◽  
Metamorphic Rocks ◽  
Additional Method ◽  
Natural Systems ◽  
Long Period ◽  
Mineral Inclusions ◽  
Large Peak ◽  
Viscous Relaxation ◽  
T Path ◽  
Temperature Time

&lt;p&gt;Over the recent years, Raman elastic barometry has been developed as an additional method &lt;span&gt;to calculate&lt;/span&gt; metamorphic conditions in natural systems. A major advantage of Raman elastic barometry is that it does not depend on thermodynamic databases and classic geobarometry methods &lt;span&gt;but&lt;/span&gt; relies on mechanical calculations. As a consequence, Raman elastic barometry offers an independent method for estimating the pressure conditions &lt;span&gt;that prevailed at the&lt;/span&gt; &lt;span&gt;time of entrapment&lt;/span&gt; of mineral&lt;span&gt;s&lt;/span&gt; du&lt;span&gt;ring&lt;/span&gt; growth of their host&lt;span&gt;s&lt;/span&gt;.&lt;/p&gt;&lt;p&gt;The di&lt;span&gt;fference between&lt;/span&gt; the pressure calculated &lt;span&gt;using&lt;/span&gt; elastic geobarometry and &lt;span&gt;that calculated by phase&lt;/span&gt; equilibria methods has recently &lt;span&gt;been employed to&lt;/span&gt; &lt;span&gt;estimate&lt;/span&gt; the extent of metamorphic reaction overstepping in natural systems. &lt;span&gt;Quantification of&lt;/span&gt; the &lt;span&gt;latter however implicitly assumes that the rheology&lt;/span&gt; of the inclusion-host system &lt;span&gt;is perfectly&lt;/span&gt; elastic. This assumption may no&lt;span&gt;t&lt;/span&gt; hold at high temperatures, where viscous creep of minerals takes place.&lt;/p&gt;&lt;p&gt;The amount of viscous relaxation of &lt;span&gt;a host-inclusion&lt;/span&gt; system is a path&lt;span&gt;-&lt;/span&gt;dependent quantity which mostly depends on the temperature-time (T-t) path &lt;span&gt;followed&lt;/span&gt;. &lt;span&gt;Here&lt;/span&gt;, we present examples of visco-elastic relaxation of mineral inclusions and calculate the apparent reaction overstepping which results by assuming that the mechanical system is purely elastic. &lt;span&gt;Our modelling shows&lt;/span&gt; that host-inclusion systems &lt;span&gt;that&lt;/span&gt; experienced large peak temperatures for long period&lt;span&gt;s&lt;/span&gt; of time will retain inclusion residual pressures that &lt;span&gt;cann&lt;/span&gt;ot be simply related to the growth of the&lt;span&gt;ir hosts&lt;/span&gt; and should &lt;span&gt;therefore not&lt;/span&gt; be used for reaction overstepping calculations.&lt;/p&gt;

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