Document Details
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Document Type |
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Article In Journal |
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Document Title |
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Abnormal Concentrations of Boron, Gold and Heavy Metals in the Pleistocene and Recent Terraces at Wadi Al Hamd, Northwestern KSA التركیزات الغیر اعتیادیة التّمركز الشّاذّة للبورون، ذهبيّ و ثقيل المعادن في المساكن الحديثة و العصر الجليديّة في الوادي الحامد ,كيه إس إيه الشّماليّ الغربيّ |
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Subject |
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Abnormal Concentrations of Boron, Gold and Heavy Metals in the Pleistocene and Recent Terraces at Wadi Al Hamd, Northwestern KSA |
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Document Language |
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English |
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Abstract |
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The contents of boron, gold and some other heavy metals in
the Quaternary terraces at Wadi Al Hamd area are abnormally high.
The boron content can be used as paleo-indicator of salinity and pH
conditions during deposition. These B-rich terraces lack detrital
tourmaline which is the commonest source of the element.
The Quaternary terraces of Wadi Al Hamd comprise a lower
consolidated very coarse part of Pleistocene age followed by a much
finer Recent upper unconsolidated alluvial terraces. The Pleistocene
terraces contain abnormal B content (161-345 ppm) in their coarse
carbonate cement of conglomerate which is a strong indication of up
to 12 during cementation. A relatively lower paleo-pH value of 8-9 is
assigned to the topmost part of the Pleistocene terraces as B content in
its quartz-arenite is lower (161-185 ppm). The upper Recent alluvial
terraces are composed of silt and mud with kaolinite/illite (K/I) ratio
in the range of 2.5 to 3 and have lower B content (16-40 ppm) owing
to the dominance of kaolinite. The given boron content in the latter
suggests low pH (amounting 5-6.5).
It is believed that B is incorporated into the crystal structure of
calcite cement possibly in the form of B (OH)-4 which is dependant on
the pH value, being more enhanced by the incorporation of H+ into the
calcite structure. It is also believed that the organic matter plays a
significant role in B fixation on plant remains of the clayey parts of
the upper terraces.
The Ba and Sr contents show lowest values in the quartz-arenite
at the top of the Pleistocene terraces suggesting elemental
fractionation in more reducing conditions. This also suggests sea
transgression after the deposition of very coarse conglomerate in a
lacustrine and hence the quartz-arenite was deposited under reducing
conditions. There is also distinct variation in the contents of two
analyzed REE (namely Ce & La) and geochemically-related Y.
The silt-sized fractions of the mud cracks and the upper
unconsolidated terraces are characterized by the presence of free
native gold. Considerable amount of economic gold amounting up to
1.4 and 6.1 g/t are assigned to both lithologies, respectively. On the
other hand, the exposed older Pleistocene terraces lack gold that might
be accumulated at unexposed depths due to gravity settling. |
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ISSN |
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1012-8832 |
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Journal Name |
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Earth Sciences Journal |
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Volume |
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20 |
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Issue Number |
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1 |
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Publishing Year |
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1430 AH
2009 AD |
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Article Type |
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Article |
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Added Date |
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Monday, February 7, 2011 |
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Researchers
| طلال القاضي | Qadi, Talal | Researcher | Doctorate | |
| اسعد مفتي | Mufti, Asaad | Researcher | Doctorate | |
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