كليدواژه :
اوليژيست , كوارتز , سازند آغاجاري , سري هرمز , سنندج سيرجان , منشأيابي
چكيده فارسي :
سازند آغاجاري با سن ميوسن مياني تا پليوسن، آخرين واحد گروه فارس است. سنگ‌رخساره‌هاي شناخته شده در نهشته‌هاي اين سازند شامل ماسه‌سنگ آهكي، مارن، آهك و سيلتستون آهكي است. ستبراي اين سازند در برخي از مناطق پس‌خشكي بندرعباس به بيش از 3000 متر هم مي‌رسد. مطالعات صحرايي و ميكروسكوپي روي 50 نمونه‌ي برداشت شده از اين سازند در محدوده‌‌ي مورد پژوهش و نمونه‌هاي گرفته شده از سري هرمز (مربوط به چند گنبد) نشان مي‌دهد كه اين سازند داراي دانه‌هاي آواري (عمدتاً كوارتز پلي‌كريستالين و كوارتزهاي با خاموشي موجي)، خرده‌هاي سنگواره‌ها، كاني‌هاي تيره (اكسيد و هيدروكسيدهاي آهن)، آلبيت، ارتوكلاز و كاني‌هاي فرعي مسكويت و كلريت است كه همگي در يك زمينه‌ي آهكي قرار دارد. آزمايش‌هايXRF و ميكروپروب سه نمونه از اوليژيست‌هاي موجود در سازند آغاجاري و سري هرمز، بيانگر اين است كه منشأ اوليژيست‌ها احتمالاً به فرسايش سري هرمز بازمي‌گردد. فراواني كوارتزهاي داراي خاموشي موجي در سازند آغاجاري نيز منشأ دگرگوني را براي آنها نشان مي‌دهد و احتمالاً توسط عوامل حمل و نقل از پهنه‌ي ساختاري سنندج ـ سيرجان به اين حوضه‌ي رسوبي منتقل شده‌است.
چكيده لاتين :
1- Introduction
Aghajari Formation as the last unit of Fars Group cropps out in Hormuzgan Province with a
considerable thickness. This Formtion is composed of red sandstones and green to reddish grey
silty marls. According to Kalantari (1992), this formation has the age range of Middle Miocene
to Pliocene. The thickness of this formation reaches to 3000m in northern Bandar Abbas
(Gholamalian, 2012). The great thickness, broad expansion, slothness (with attention to the
calcareaus matrix) and presence of some amounts of Iron rich minerals as grains are
charactristics of this formation mineralogical composition. Also these rocks contain
polycrystalline quartz, wavy extinction quartz, fossil fragments and some minor minerals such
as moscuvite, chlorite, albite, orthoclase in addition to oligiste. In order to identify the origin of
the mentioned minerals; several samples are studied by microscope and Some are processed
by chemical analysis. In addition, the origin of oligiste particles in was considered; so some
samples containing this mineral were collected from Hormuz Series of Siahoo, Anguran,
Zendan and Hormuz salt diapirs.
2- Methodology
The studied area is located in 74 km North of Bandar Abbas, near the Siahoo and Aghasin
villages. We should Go 64 km northward from Bandar Abbas and then 10 km eastward in order
to access the studied section. The studied section is approximately 4 km before the Aghasin
village. Fifty samples were collected from Aghajari Formation and Hormuz Series for
the sake of this study; 22 of them were for chemical analysis and 20 for microscopic thin and
polished sections. Three oligiste samples are collected from salt domes for comparison to the
Iron rich mineral grains of Aghajari Formation. Oxidic and elemental XRF analysis of samples
performed on 22 samples. In addition, point analysis of microprobe exercises are done on the
rock forming grains of Aghajari Formation and Hormuz salt plug oligisites with XRF method.
Thin and polished sections are studied by polarizan and reflective micoscopes.
3- Results
Microscopic investigations on the thin sections of Aghajari Formation Showed the mineralogical
content of rocks. Average mineralogical component of grains in this sandstones includs %45 to
%50 quartz (%20 wavy extinction quartz and %25 to %30 polycrystalline quartz), less than
%10 albite and orthoclase, %3 to %5 black oligiste and %30 to %35 calcareous matrix.
Quartz is the main mineral in the grains. Polycrystalline and wavy extinction quartzes can
generally form in metamorphic phases. On the other hand, angular to semi-rounded quartz
Grains show short distance transportation. It seems these quartz grains are originated from the
Sanandaj – Sirjan metamorphic belt rocks. Weak mineralogy and grain size sorting and high
thickness of Aghajari Formation show fast sedimentation and short distance transportation of
grains. On the other hand, comparison of microprobe spot XRF analysis of oligiste grains
shows the chemical composition similarity of this mineral in Hormuz series and Aghajari
Fomation sandstones. So these mineral grains are transported from Hormuz series salt plugs to
the sedimentary environment during deposition of Aghajari Fomation in the Late Miocene to
the Pliocene.
4- Discussion & Conclusions
Results of XRF analysis, microprobe and microscopic investigations prove the presence of
Fe2O3 as oligiste grains in the Aghajari Formation sandstones. Results of point analysis of
these particles are similar to those of Hormuz series; showing the probable origin of oligiste
particles in the sandstones. A large amount of quartz is present in the Aghajari Formaion
sandstones that cannot be transported from salt plugs, because there are a few amount of this
mineral in the Hormuz Series.
Wavy extinction quartz grains are abundant in the Aghajari Formation sandstones and have
been originated from Sanandaj - Sirjan metamorphic belt.
Presence of some mineral particles such as: albite, moscuvite, and chlorite in the Aghajari
sandstones prove short distance transportation, probably from the Sanandaj - Sirjan
metamorphic belt.
In fact, Aghajari sandstone particles are synchroneously transported from two main sources;
Sanandaj - Sirjan metamorphic rocks are the origin of quartz grains and oligiste fragments are
originated from the Zagros Range salt domes.
