عنوان

Petrology and stable isotope geochemistry of the Nanga Parbat-Haramosh Massif, northern Pakistan

Number

TLpq304249738

.Language of Text, Soundtrack etc

انگلیسی

Title Proper

Petrology and stable isotope geochemistry of the Nanga Parbat-Haramosh Massif, northern Pakistan

General Material Designation

[Thesis]

First Statement of Responsibility

M. U. K. Khattak

Subsequent Statement of Responsibility

J. W. Shervais

Name of Publisher, Distributor, etc.

University of South Carolina

Date of Publication, Distribution, etc.

1995

Specific Material Designation and Extent of Item

158

Dissertation or thesis details and type of degree

Ph.D.

Body granting the degree

University of South Carolina

Text preceding or following the note

1995

Text of Note

The Nanga Parbat-Haramosh Massif in northern Pakistan records the Tertiary metamorphism and dynamics of the Himalayan collision and subsequent overthrusting of the Asian plate onto the Indo-Pakistan plate. The massif consists of an intercalated sequence of para- and orthogneisses, of minor metabasics and calc-silicate rocks, and of post-metamorphic pegmatite dikes. These gneisses are metamorphosed under high pressure upper amphibolite facies conditions. The P-T estimates and the P-T-t paths of the pelitic samples from the massif and the adjacent areas of the Kohistan and Ladakh arcs along two cross-strike transects (Indus and Astore Rivers) through the massif show that the massif followed a compressional (counterclockwise) and the Kohistan-Ladakh arc a decompressional (clockwise) P-T-t path. Geothermobarometry on zoned garnets from core to rim indicates that the massif rocks started their metamorphic history with 5.5 kb and 650C. During collision, the pressure and temperature rose to >10 kb and about 750C. The Ladakh garnets started to grow at >10 kb, 750C with subsequent decrease in metamorphic pressure to 8.5 kb. After the collision, the massif and the Kohistan-Ladakh rocks equilibrated at similar conditions of usd O thermometry results are consistent with the phase equilibrium studies of the massif and the Kohistan-Ladakh arc. Temperatures were calculated from O fractionations among quartz, garnet, feldspar, biotite, muscovite and amphibole. Among the analyzed samples, the whole rock usd\rm\delta\spO\sb{SMOW}usd isotopic values range from 7 to 15.3usd\perthoususd, quartz 7.4 to 16.4usd\perthoususd, feldspar 7 to 16.1usd\perthoususd, garnet 5.3 to 13.7usd\perthoususd, biotite 3.9 to 12.6usd\perthoususd, muscovite 6.7 to 12.7usd\perthoususd, and hornblendic amphibole from 4.4 to 7.2usd\perthoususd. Calculation of the O composition of fluids that were in equilibrium with different minerals in the temperature range of 500-700C reveals that there is one pre-metamorphic and one post-metamorphic fluid activity affecting the isotopic composition of the rocks of the massif. The pre-metamorphic fluids probably originated from an igneous parent, depleting the rocks in 2usd\perthoususd, especially along the major faults. The post-metamorphic fluids probably originated from prograde metamorphic reactions and were heavy enough to enrich the feldspars up to 18usd\perthoususd.

Earth sciences

Geochemistry

Geology

Mineralogy

oxygen-18

J. W. Shervais

M. U. K. Khattak

Electronic name

p

[Thesis]

276903

a

Y