ANALYSIS OF STREAM SEDIMENT PROVENANCE

Introduction

Provenance analysis of sediments is aimed at reconstructing the parent-rock assemblages of sediments and the climatic physiographic conditions under which sediments formed.
Almost every rock on Earth is broken down into sediment, and the sediment is then carried away somewhere else by gravity, water, wind or ice. This process of transport breaks rocks into ever smaller particles from boulder to clay size, by physical abrasion. And at the same time most of the minerals in the sediment are chemically changed, leaving just a few resistant ones. Also, long transport in streams can sort out the minerals in sediment by their density, so that light minerals like quartz and feldspar can move ahead of heavy ones like magnetite and zircon.
Stream sediments are mixture of sediment soils and rocks from the drainage basin upstream of the collection site. Sediments constitute an integral and dynamic part of stream basins, originating from the weathering of minerals and soils upstream. Natural concentrations of heavy metals as a result of the weathering processes of mineral deposits can be quite high in stream sediments close to the deposit, but decrease with increasing distance downstream, due to dissipating energy and dilution of sediments from other un-polluting sources. Sedimentary provenance studies started in the 19th century with the microscopic investigation of accessory (Heavy) minerals of recent sands. Commonly, the stream sediments include unaltered primary minerals, precipitated materials and adsorbed elements. The dispersion of immobile and semi-mobile elements. Major elements such as Si, Al, Fe, Ca, Mg, K, Na, and trace elements such as As, Ba, Cd, Ce, Co, Cr, Cu, Li, Mn, Ni, P, Pb, Sn, Sr, Ti, V, Zn are the elements possible to contain in the stream sediments. Those are associate with so many minerals such as zircon, ilmenite, magnetite, garnet, limonite, olivine, hematite, pyrite, augite, rutile, spinel, siderite, topaz, tourmaline etc.
There are four potential important processes that can modify a heavy mineral assemblage,
• source area weathering
• transport abrasion
• hydraulic sorting
• post-depositional digenesis

Objectives

• Identification of provenance of Sirimalgoda oya

• Identification of minerals under optical microscope

• To gain a comprehensive practice on sediment classification.

• To have a comprehension on the sediments properties

Study Area

Location: Sirmalgoda oya which is tributary of the Badulu oya

Coordination N 6058’26.9652

E 8105’17.0628

Procedure

Stream sediments of Sirimalgoda oya were collected by panning
They were dried in the oven under 900oC and kept until reach the room temperature
Then the representative sample was made
Non-magnetic and magnetic minerals were separated using hand magnet
1*1 inch square was drawn on the center glass plate that used in microscope and it was differentiated for small equal segments
Drop of glycerol was placed on that glass plate
Small amount of minerals were taken out from the non-magnetic mineral sample and distributed it on that segments equally
Then the sample was observed under reflective microscope. Non-magnetic sample was also observed
Mineral counts were taken in one segment of the glass plate.

Observations

In non-magnetic sample,

Glassy, sub angular grains (A)
Angular sharp cornered irregular orange color grains (B)
Thin transparent platy grains (C)
Reddish brown irregular prismatic grains (D)
Rod shaped yellow color grains (E)
Well rounded black color grains (F)

In magnetic sample,

Reddish black grains (G)
Bluish Black angular grain (H)

Calculations

Mineral percentage calculation

Assume the mineral name as M,

Count of the M grains in one segment = x
Total no of grains in the same segment = y

M mineral percentage in the sample = (𝑥 /𝑦) * 100

In our sample, Nonmagnetic,

Total mineral count in one segment = 75

According to that here are the percentage calculations in observed mineral

A = 70.66%
B = 20.00%
E = 2.66%
D = 1.33%
Other = 5.33%

Magnetic sample

Total mineral grains count = 150

According to that here are the percentage calculations in observed mineral

G = 86.66%
H = 9.54%
Other = 3.8%

Conclusions

Using handout which was given us and other references, the observed mineral grains identified.

A - Quartz
B - Garnet
C - Muscovite
D - Rutile
E - Zircon
F - Ilmenite
G - Hematite
H - Magnetite

There were some unidentified mineral grains also. Quarts are the mainly present in non- magnetic mineral sample and hematite are the most presence in magnetic sample.

Discussion

Finger print method was used to collect samples from the stream. That means potential sediment sources can be characterized using a number of diagnostic physical and chemical properties. Comparison of these fingerprints with equivalent information for suspended sediment samples permits the relative importance of the potential sources. Samples were collected along the stream basin but opposite to the stream flow. The separation of two samples points was approximately 1km.

Heavy mineral concentrate may be prepared from bulk stream sediment using screening, gravity, and magnetic techniques in the laboratory. As alternative simpler and quicker method is to concentrate the heavy minerals by panning in the field. Panning is carried out using a flat bottomed metal or plastic pan. A large pan is filled with sediment and water from a stream and swirled around, so that the moving water sorts the grains by their density.

We could not take the samples along the stream basin for study the provenance. Only take the samples in one place of Sirimalgoda oya. Also we could not do the sieving part of the practical due to lack of time.

References

Google. 2014. Google. [ONLINE] Available at: https://www.google.lk/?gws_rd=cr&ei=iuQnUrK2DcqCrge_4IH4CQ#q=Stream+se diment+provenance+. [20/07/2014, 10.55 PM]
Stream Sediments Geochemical Investigations for Gold and Associated Elements in Wadi Haimur Area, Southeastern Egypt 2014. Stream Sediments Geochemical Investigations for Gold and Associated Elements in Wadi Haimur Area, Southeastern Egypt. [ONLINE] Available at: http://www.moluch.ru/archive/28/3128/. [20/07/2014, 11.34 PM].

Introduction

Objectives

• Identification of provenance of Sirimalgoda oya

• Identification of minerals under optical microscope

• To gain a comprehensive practice on sediment classification.

• To have a comprehension on the sediments properties

Study Area

Location: Sirmalgoda oya which is tributary of the Badulu oya

Coordination N 6058’26.9652

E 8105’17.0628

Procedure

Stream sediments of Sirimalgoda oya were collected by panning
They were dried in the oven under 900oC and kept until reach the room temperature
Then the representative sample was made
Non-magnetic and magnetic minerals were separated using hand magnet
1*1 inch square was drawn on the center glass plate that used in microscope and it was differentiated for small equal segments
Drop of glycerol was placed on that glass plate
Small amount of minerals were taken out from the non-magnetic mineral sample and distributed it on that segments equally
Then the sample was observed under reflective microscope. Non-magnetic sample was also observed
Mineral counts were taken in one segment of the glass plate.

Observations

In non-magnetic sample,

Glassy, sub angular grains (A)
Angular sharp cornered irregular orange color grains (B)
Thin transparent platy grains (C)
Reddish brown irregular prismatic grains (D)
Rod shaped yellow color grains (E)
Well rounded black color grains (F)

In magnetic sample,

Reddish black grains (G)
Bluish Black angular grain (H)

Calculations

Mineral percentage calculation

Assume the mineral name as M,

Count of the M grains in one segment = x
Total no of grains in the same segment = y

M mineral percentage in the sample = (𝑥 /𝑦) * 100

In our sample, Nonmagnetic,

Total mineral count in one segment = 75

According to that here are the percentage calculations in observed mineral

A = 70.66%
B = 20.00%
E = 2.66%
D = 1.33%
Other = 5.33%

Magnetic sample

Total mineral grains count = 150

According to that here are the percentage calculations in observed mineral

G = 86.66%
H = 9.54%
Other = 3.8%

Conclusions

Using handout which was given us and other references, the observed mineral grains identified.

A - Quartz
B - Garnet
C - Muscovite
D - Rutile
E - Zircon
F - Ilmenite
G - Hematite
H - Magnetite

There were some unidentified mineral grains also. Quarts are the mainly present in non- magnetic mineral sample and hematite are the most presence in magnetic sample.

Discussion

References

Google. 2014. Google. [ONLINE] Available at: https://www.google.lk/?gws_rd=cr&ei=iuQnUrK2DcqCrge_4IH4CQ#q=Stream+se diment+provenance+. [20/07/2014, 10.55 PM]
Stream Sediments Geochemical Investigations for Gold and Associated Elements in Wadi Haimur Area, Southeastern Egypt 2014. Stream Sediments Geochemical Investigations for Gold and Associated Elements in Wadi Haimur Area, Southeastern Egypt. [ONLINE] Available at: http://www.moluch.ru/archive/28/3128/. [20/07/2014, 11.34 PM].