Open AccessPetrographical and mineral chemistry characteristics of mafic dykes in Nhi Ha area, Ninh Thuan and its meaning
Author(s) -
Nguyen Minh Tai,
Phạm Trung Hiếu
Publication year - 2020
Publication title -
khoa học và công nghệ: tự nhiên
Language(s) - English
Resource type - Journals
ISSN - 2588-106X
DOI - 10.32508/stdjns.v2i6.883
Subject(s) - mafic , geochemistry , geology , amphibole , pyroxene , augite , plagioclase , sericite , ilmenite , mineralogy , olivine , hydrothermal circulation , paleontology , quartz , seismology
The NE-SW and NW-SE mafic dyke rocks in Nhi Ha area intruded through Cretaceous granitoid Dinh Quan or overlapped by Quaternary sediment materials. It has block type and blue grey in color in the field. Under microscope, based on minerals and textures, divided into 2 types of mafic dyke rock, such as diabase and porphyritic diabase. Minerals chemical analysis by EPMA method: plagioclase almost are labradorite (An 60.80%), oligoclase (An from 12.31 to 14.29%), some grain had albitation (An from 6.75 to 8.46%); pyroxene with augite (Wo41,80 En44,22 Fs13,98 to Wo43,40 En37,50 Fs19,10) and diopsite composition (Wo45,45 En42,48 Fs12,07 to Wo48,16 En40,02 Fs11,81); amphiboles in basalt are magnesio-hastingsite (Ca-amphibole group). Popular alteration minerals are chlorite, epidote and sericite. Chlorite is pycnochlorite type, ratio Fe/(Fe+Mg) <0,6 show that it formed by hydrothermal alteration process with temperature from 150 to 3250C. Opaque minerals are pyrite, chalcopyrite, ilmenite, magnetite, titanomagnetite, titanite (sphene) and a little bit of rutile.