heavy mineral applications in sedimentary petrology

University of Louisiana at Lafayette

Heavy Mineral Applications in Sedimentary Petrology Advanced Sedimentary Petrology, Fall 2013

Shanna Mason 11-‐18-‐2013

Abstract

Heavy Mineral analysis in sedimentary petrology is both important and precarious at the same time. The unique physical characteristics that enable their importance can also lend to their detriment. The applications of heavy minerals in sedimentary petrology are discussed within this text in two sections. The first, dealing with applications of heavy minerals in

modern depositional systems, and the second discussing provenance applications. Heavy Mineral analysis in modern depositional systems has had a plethora of research centering on hydraulic equivalents. One of the most prominent studies by Gordon

Rittenhouse analyzed heavy minerals in modern sedimentation problems of the Rio Grande. However, his research was negated through many other studies.

Provenance determination in terms of heavy minerals occurring in sediments must have the depositional environment considered carefully. Due to the unique physical characteristics of

heavy minerals, their occurrence in any assemblage is depending on their stability. Through analysis of multiple research studies on the applications of heavy minerals, it will be evident how their unique characteristics can be detrimental to their analysis. However, with an understanding of the sediment history, this text will prove through various studies that petrologists can compensate for these variables, strengthening the importance of heavy

mineral analyses.

INTRODUCTION

Heavy minerals, the fraction of a sandstone comprised of many different mineral grains with

specific physical and chemical characteristics, have long been recognized as an important

indicator of the parentage and history of sediments within a depositional environment (Briggs,

1965). The amount of research on accessory minerals, as they are also called, available for

discussion is immense. Given the early popularity of heavy mineral analysis, the recent decline

in their use gives reason to analyze the cause. This decline is, in part, due to technological

advances, but it is also due to the general realization of their susceptibility to the processes of

transport, deposition, and diagenesis. However, by assessing the history of the sediment,

analysis of these minerals can be enhanced by compensating for their environmental variables

in various ways (Bateman, 2007). This paper will focus on applications of heavy minerals in

sedimentary petrology in two sections. First their application in modern depositional systems,

and various studies conducted, will be discussed, then heavy mineral analysis in terms of

provenance. Showing how, through research, we can identify the weaknesses of heavy minerals

in certain environments and use this knowledge to improve the accuracy of their use.

Unfortunately, every application of heavy minerals in sedimentary petrology cannot be

discussed. The application of heavy minerals can expand well into other areas besides modern

depositional systems and provenance. Subsurface correlation of mineral zones, tectonic history

determined by heavy mineral analysis, and varietal studies of many other species besides

tourmaline all indicate promise towards research in the field of heavy mineral analysis that can

only add to its value.

HEAVY MINERALS IN MODERN ENVIRONMENTS

FLUVIAL SETTINGS

Much of the research dealing with heavy mineral analysis in modern depositional systems has

centered on Hydraulic Equivalents. Beginning in 1933 with William Rubey, who coined the term

‘hydraulic equivalence’ to show how minerals with different physical properties can be the

result of the same hydraulic conditions. These hydraulic equivalents were calculated using

settling velocities of heavy minerals according to Stokes Equation (see fig. 1). Stoke’s Law states

that settling velocities of spherical particles are a function of particle diameters, effective

densities, and inversely as the viscosity of fluids (Rubey, 1933). Rubey determined that the

equation outlined in figure 1 worked for particles between the diameters of 0.0002 and 0.2

millimeters. For larger particles, hydraulic equivalents will deviate until quartz particles reach

1.5mm in size, at which point fall velocities will be proportional to the square root of diameter

particles (Rubey, 1933; Tourtelot, 1968). The hydraulic equivalents of quartz, magnetite, silver

and gold, calculated by Tourtelot (1968) using the values from the equations outlined by Rubey

can be seen in Figure 2. Even though Rubey did not use his work to analyze depositional

environments, Rittenhouse knew that it could be (1944).

In his study on the modern sedimentation problems of the Rio Grande River,

Rittenhouse figured out an empirical way to assess source areas on different streams in the

Middle Valley using the Hydraulic Ratio. Between 1936 and 1941, the Rio Grande and the

tributaries that feed it, were depositing around 12,000 acre-‐feet of sediment per year. This

caused multiple issues such as; the channel and floodway capacity to discharge flood waters

was diminished, the ground-‐water table had been raised, infertile sands were being deposited

onto pastures and cultivated land, and accelerated soil erosion was occurring in relation to

channel aggradation (Rittenhouse, 1944). In conjunction with the Soil Conservation Service in

Greenville, South Carolina, Rittenhouse set out to tackle the sedimentation problems by using

heavy mineral analyses to figure out which tributary was depositing the most sediment so that

controls could be implemented to stop damage from continuing to occur. He took the hydraulic

equivalent size, determined by Rubey, and calculated a ratio that he believed to be more

reliable than other quantitative methods. The Hydraulic Equivalent sizes calculated

experimentally from two sites of the Rio Grande experiment is outlined in Figure 3. Rittenhouse

defined the Hydraulic ratios as “100 times the weight of a mineral in a known range of sizes,

divided by the weight of light minerals of equivalent hydraulic size (Rittenhouse, 1943: 1725).”

Rittenhouse said that when the hydraulic ratio is used, it helps to eliminate variations in

assemblage caused by hydraulic selectivity, or the selectivity of a stream to deposit all the

heavy minerals in the bed load (Briggs, 1965). Multiple analyses concerning the size distribution

of heavy minerals have since occurred, offering varying validity opinions of this method.

Rittenhouse based the Hydraulic Ratio on the constant relative availability of the heavy

minerals along a transverse section of a stream. During an investigation of sediments in the

Rhine River, Van Andel rejected this basis of constant availability, stating that this did not apply

to his area of study (1959). The negation of the basis of hydraulic ratios puts the validity of

Rittenhouse’s theory in question. If it cannot be applied elsewhere, it is of no use to

sedimentary petrologists (Young, 1966). Edward Young conducted a study of four quantitative

methods used in heavy mineral analysis using two samples from Rittenhouse’s Rio Grande

study. He discounted the hydraulic ratio method in part due to the laboriousness of

calculations, but also due to relative deviation results (see fig. 4). Rejecting the hydraulic ratio

method, Young obtained results favoring the weighted number percentage and weight

percentage methods for heavy mineral analysis (Young, 1966). Louis Briggs also called into

question the validity of Rittenhouse’s argument, postulating that modal separation of heavy

and light minerals increases with grain size for samples with diameters larger than 0.125mm.

He also determined that the frequency of any mineral in a sandstone depends on interactions

between minerals with different specific gravities, particle shape, availability of size to transport

mechanism, and the hydraulic selectivity of the agent (Briggs, 1965). White and Williams (1967)

studied the settling velocities of light and heavy minerals in cross bedding. Determining that

settling velocity equivalents varied between bottomset and foreset laminations due to

deposition, which can be resolved into components of suspension and traction loads (White

and Williams, 1967). Variations from hydraulic equivalent sizes can also be found when looking

at studies that focus on lacustrine and coastal depositional settings.

COASTAL AND LACUSTRINE SETTINGS

In 1959, Donald McIntyre attempted to relate the hydraulic equivalent sizes determined by

Rubey to Lake Eerie foreshore deposits. The deposits to be sampled occurred in alternating

light and dark layers that were called “lenses.” Three separate lenses were sampled and

categorized as layers A, B, and C. Hydraulic equivalent quartz sizes were then compared for five

present heavy minerals in each layer using both quartz and garnet as the basis. The accuracy of

calculated hydraulic equivalent sizes varied within each layer. The variances can be seen when

looking at Figure 5, which describes hydraulic equivalences obtained either by calculations or by

subtracting the mean grain size of quartz or garnet from the mean grain size of each of the

heavy minerals in the same layer. Using quartz as the basis, only the C layer came close to the

theoretical values. For values of the A and B layers, hydraulic sizes using quartz taken from the

samples were continuously greater than the calculated sizes. However, when garnet was used

as a base, calculated hydraulic equivalent sizes more closely related to those observed in the

samples (Mcintyre, 1959). Looking at this experiment and the numerical values exhibiting

deviations from hydraulic equivalent sizes, it is evident how subjective to environmental

conditions hydraulic equivalents are.

Bryce Hand (1967) set out to determine hydraulic equivalents using settling velocities in

his study that examined sand samples from beaches and dunes along a strip of the New Jersey

coast. Hand thought that beach deposits should mimic hydraulic equivalence theory laid out by

Rubey and Rittenhouse, because they are both deposited by a fluid medium (Hand, 1967). The

determination of his study was that the correlation was incorrect. His results showed that

actual settling velocities related to lower hydraulic equivalents sizes more so than their

calculated equivalents, which is outlined by figures 6 and 7 that show cumulative percentage

curves according to settling velocities. Hand attributed this to the stability of heavy minerals

and their ability to withstand various conditions in a deposit relative to their light mineral

counterpart. He uses the example of quartz and garnet to illustrate this point. Showing that to

make garnet and quartz actual equivalent counterparts, you must decrease the settling velocity

of garnet slightly to account for its ability to remain in a deposit longer than quartz (Hand,

1967).

These significant studies on heavy minerals, and their hydraulic equivalent sizes as seen

in modern deposition, show the amount of variation present in each environment. In some

cases, heavy minerals can be very useful in modern sedimentation problems. They can also

enable us to understand hydraulic conditions acting on various sediments loads more than light

minerals can. However, their physical characteristics lend the need for unique knowledge on

how they react in each environment. Petrologists must take a second look at their reactions to

transportation and depositions mechanisms to ensure each variable is accounted for in

quantitative analyses, leaving more space for error.

HEAVY MINERALS AND PROVENANCE

PROBLEMS WITH HEAVY MINERAL ANALYSIS IN PROVENANCE DETERMINATION

Historically, heavy mineral analysis has been most widely used by Petrologists as provenance

indicators (Briggs, 1965). Their unique physical characteristics and lesser abundance in

sedimentary rocks than light minerals give them a distinct advantage in the determination of

source rocks (Blatt, 1985). However, these unique characteristics can also be their downfall.

The declination of heavy mineral applications in sedimentary petrology in the last 20th century

is due to the revelation that these minerals are specifically more apt to post-‐depositional

processes (Van Andel, 1959). Therefore, many variables must be considered when using heavy

mineral analyses. Recent research of these variables suggest that when considered correctly,

these variables can be used to attribute to the accuracy of heavy mineral analysis rather than

take away from it. Here we will discuss how research surrounding the post-‐depositional

alteration of heavy minerals can be applied in a way that aids in the accuracy of their analysis,

then we will look at one of the many important stable minerals and its applications in

provenance determination.

Richard Bateman and John Catt (2007) identified five phases of the sedimentary cycle

that can affect a heavy mineral assemblage, and processes within each one that particularly

have an impact. They use an approach designed to compensate for the specific sedimentary

history of an assemblage in the determination of the parent rock. To do this, they examine the

various processes identified in each phase of the sedimentary cycle. By understanding the

processes they intended to show (1) the value in applying multivariate statistical techniques to

identify trends of heavy mineral data and (2) to demonstrate the value of heavy mineral data

when accompanied with other paleoenvironmental data analysis. They published research on

five case studies and the implication of the identified modifying processes on provenance

identifications in tertiary and quartenary deposits found in the British Isles (Bateman, 2007:

153). During their analysis they claim that the provenance interpretation ability of heavy

minerals is so unique that it is worth the research surrounding post-‐deposition alteration

processes, because most of them are predictable and can be compensated for in some fashion.

STABILITY OF HEAVY MINERALS IN PROVENANCE DETERMINATION

The composition of a heavy mineral assemblage must be analyzed with the various physical and

chemical processes that were active post-‐deposition of the sediment. The appearance of any

heavy mineral in an assemblage is the direct result of its ability to withstand abrasion during

transport, weathering, and diagenesis after deposition (Pettijohn, 1942). The stability of an

accessory mineral, or its ability to resist alteration, has been analyzed by a variety of authors,

each one determining an “order of stability” to interpret the presence of certain minerals in an

assemblage. This stability factor is controlled by pressure, temperature, connectivity and PH

level of pore fluids, presence of oil, variation in the mineral’s chemical composition, and the

amount of time the sediment spent in deep burial. Pettijohn, in “Sedimentary Rocks,”

illustrated the most notable authors to determine orders of stability, both in terms of

weathering and intrastratal solution, which is outlined in Figure 8. The research behind the

progressive stability of heavy minerals overtime led to the development of the Zircon-‐

Tourmaline-‐Rutile index.

Zircon, Tourmaline, and Rutile, all heavy minerals that are very mechanically and

chemically stable, have been shown to concentrate with quartz as sandstones become more

quartzose. Therefore, it has been determined that grains of these heavy minerals can be

composed into an index that progresses amongst various sandstone classifications (Hubert,

1962). This index can then be correlated to other samples to determine the depositional

environment that created the sediment in question. As the index of these minerals increases, it

is also noted that other transparent heavy mineral presence decreases. Which is why Hubert

proposed this ZTR index as an indication of the “maturity” of sandstone, in his interpretation

meaning the degree to which the sediments had been modified. The index ranges from low

values in arkoses and graywackes, to over 90% in most orthoquartzite sandstones (Hubert,

1962).

In contrast to compensation of variables involving intrastratal solution, Van Andel (1952)

proposed that in some cases the absence of unstable minerals was instead the result of

processes occurring prior to deep burial. To account for this, heavy mineral analysis used in

provenance determination of basins must look at regional heavy mineral distribution. This

regional province method required the inclusion, interpretation and sampling of multiple

geographic regions. Van Andel applied this theory to the Rio Grande in which he argued the

importance of the applicability of heavy minerals in sedimentation analysis. Flores and Shideler

(1978) supported this theory as well in their analysis of the same region, concluding that

selective decomposition, determined by the ZTR index, did not contribute to regional variations

in the Rio Grande (Flores, 1978).

TOURMALINE

Krynine (1946) studied the application of Tourmaline and its multiple varieties in provenance.

He outlined 5 major types of provenance producing Tourmaline, and the subsequent varieties

that are characteristic of each. Due to its high geochemical stability, Tourmaline can withstand

ranges of temperatures and pressures. Varieties of Tourmaline are not only applicable as an

index guide in primary occurrences, but also as reworked sediments. Krynine notes that

Tourmaline can survive multiple sediment cycles, depending on the variety. Also notable is the

authigenic occurrence of Tourmaline. As a secondary mineral, its occurrence is widespread and

therefore predictable over a geographic range. Tourmaline varietal studies can be applied to

provenance determination, such as the identification of the Gatesburg formation as the parent

rock of the Bellefonte Sandstone. They can also be applied in determination of the tectonic

history of a formation, such as the Tuscarosa Quartzite in relation to the Appalachian

Geosyncline in East Central Pennsylvania. More information on both of these determinations

can be found in Paul Krynine’s work “The Tourmaline Group in Sediments,” published in the

Journal of Geology in 1946.

CONCLUSION

Even though the unique physical characteristics that comprise a heavy mineral assemblage

leads to their environmental weaknesses, it is also those characteristics that enable them to be

of such value to sedimentary petrology. Applying knowledge gained through the research of

their susceptibilities to their analysis in varying applications can actually benefit their use.

However, this does require careful analysis of the geochemical and physical properties present

in a sample and how they relate to the sediment history.

REFERENCES

Allen, V. T., 1948, Weathering and Heavy Minerals, Journal of Sedimentary Petrology, v. 18, no.

1, p. 38-‐42.

Bateman, J. R. and J. A. Catt, 2007, Provenance and Palaeoenvironmental Interpretation of

Superficial Deposits, with Particular Reference to Post-‐Depositional Modification of

Heavy Mineral Assemblages, in Heavy Minerals in Use, eds., Mange, M. and D. T. Wright,

Oxford, Linacre house, 151-‐188 p.

Blatt, H., 1969, Intrastratal Solution and Non-‐Opaque Heavy Minerals in Shales, Journal of

Sedimentary Petrology, v. 39, no. 2, p. 591-‐600.

Blatt, H., 1967, Provenance Determinations and Recycling of Sediments, Journal of Sedimentary

Petrology, v. 37, no. 4, p. 1031-‐1044.

Blatt, H., 1985, Provenance Studies and Mudrocks, Journal of Sedimentary Petrology, v. 55, no.,

p. 69-‐75.

Blatt H., G. Middleton, and R. Murray, 1980, Origin of Sedimentary Rocks: New Jersey, Prentice-‐

Hall.

Briggs, Louis, 1965, Heavy Mineral Correlations and Provenances, Journal of Sedimentary

Petrology, v. 35, no. 4, p. 939-‐955.

Flores, R. M., and G. L. Shideler, 1978, Factors Controlling Heavy Mineral Variations on the

South Texas Outer Continental Shelf, Gulf of Mexico, Journal of Sedimentary Petrology,

v. 48, no. 1, p. 269-‐280.

Hand, B. M., 1967, Differentiation of Beach and Dune Sands, Using settling Velocities of Light

and Heavy Minerals, Journal of Sedimentary Petrology, v. 37, no. 2, p. 514-‐520.

Hubert, J. F., 1962, A Zircon-‐Tourmaline-‐Rutile Maturity Index and the Interdependence of the

Composition of Heavy Mineral Assemblages with the Gross Composition and Texture of

Sandstones, Journal of Sedimentary Petrology, v. 32, no. 3, p. 440-‐450.

Krynine, P. D., 1946, The Tourmaline Group in Sediments, The Journal of Geology, v.54, no.2, p.

65-‐87.

McIntyre, D. D., 1959, The Hydraulic Equivalence and Size Distributions of Some Mineral Grains

from a Beach, The Journal of Geology, v. 67, no. 3, p. 278-‐301.

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1120.

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Members from River Sands of Northern Austria and from Sandstones of the

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57, no. 2, p. 301-‐310.

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Implications for the Study of Placers Geological Survey Professional Paper, 594-‐F: US

Department of the Interior, Washington DC: Government Printing Office.

Van Andel, T. J., 1959, Reflections on the Interpretation of Heavy Mineral Analyses, Journal of


White, J. and E.G. Williams, 1967, The Nature of a Fluvial Process as Defined by Settling

Velocities of Heavy and Light Minerals, Journal of Sedimentary Petrology, v. 37, no. 2, p.

530-‐539.

Young, E. J., 1966, A Critique of Methods for Comparing Heavy Mineral Suites, Journal of


!Stokes!Law!of!Settling!Velocities!

! = ! !18�!!!! − !!!

! !!! = !ℊ18 !�!

!! − !!!! !!! !

Where:!! ! ! ! ! ! ! Magnetite!Example:!!ν!=!Fall!Velocity!! ! ! ! ! !g!=!gravity! !!!!=!Specific!Gravity!of!Quartz!Grain! !!!=!2.66!!! = Specific!Gravity!of!Water! !! = 1.00!!! = Specific!Gravity!of!Magnetite! !! = 5.18!!! = Diameter!of!Magnetite!Grain! !!! =!Diameter!of!Quartz!Grain! !η!=!Coefficient!of!Viscosity!of!Water!(Constant!Under!Conditions)! η!=!1.00!

!

!

!

! !

!=(2.66−1.00)%↓'↑2 

=(5.18−1.00) %↓*↑2 !

%↓* =,√1.66/4.18 , %↓' =0.63

%↓'  !

Only!MagneLte!grainns!0.63!

mm!in!diameter!will!fall!with!the!same!velocity!as!Quartz!

Grains!1.00!mm!in!diameter!

Hydraulic!Equivalent!of!Magnetite!

Figure!1:!(modified!from!Rubey,!1933)!

Figure 2: (From Rittenhouse, 1944) Figure 3: (from Tourtelot, 1968)

Figure 4: (from Young, 1966)

Figure 5: (from McIntyre, 1959)

Figure 7: (from Hand, 1967) Figure 6: (from Hand, 1967)

Figure 8: (from Petitjohn, 1975)

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